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Reference Desk

January 4

Champagne and soft drink bubbles

Where do these bubbles come from it often appears that they start from the middle of the fluid in random positions what governs this? they simply flow constantly from what appears to be a point of no gaseous pressure significance. (7121989 01:55, 4 January 2006 (UTC))

The carbon dioxide bubbles form from carbonic acid present in both. As for the location of nucleation sites, where the bubbles form, they can be node points on sound waves when you ping the glass, a small particle in the fluid, etc. StuRat 02:19, 4 January 2006 (UTC)

Very interesting question. As StuRat said, the bubbles form wherever there are particles in the fluid, or on the sides where there are imperfections in the glass. A fun thing to do is put a raisin in the soda. It will become covered with bubbles until it floats up to the top, where the bubbles pop and it falls again. —Keenan Pepper 08:09, 4 January 2006 (UTC)

X-ray machines at airports

1) HOw is it that the X-rays from these machines do not in the sightest damage film from cameras or laptops yet still be strong enough to penetrate luggage?

2) How is a thin strip of plastic able to protect those working around these machines from tissue damage?

3) Finally, When viewing objects being scanned there are usually two screens used by operators, one of a darker image and another in greenish tints what does each one do? (7121989 01:55, 4 January 2006 (UTC))

The X-ray machines used to scan carry-on luggage are not as strong as the ones to scan checked luggage as the items being scanned are generally smaller and can be more easily checked by hand. This is why the carry-on x-ray does not cause damage to film, electronics or people. The screens are different because one is looking for metal (such as knives or guns) and the other is looking for organic material (explosives, drugs, live animals). See How Stuff Works for a good explanation of airport X-rays. --Canley 02:18, 4 January 2006 (UTC)

I think also that X-ray machines, both medical and for security, have become much much more sensitive, and so can use much less radiation than they used to. For medical machines, in addition to the obvious radiological benefit, it allows subtler detail to be visible. A few years ago I needed a foot x-ray, and on looking at it you could see the granular structure of my foot bones - it wasn't just white for bone, black for not-bone. That added sensitivity will be vital for looking for those soft things like explosives. -- Finlay McWalter | Talk 02:37, 4 January 2006 (UTC)

Photographic film isn't really very sensitive to X-rays; it's sensitive to visible light. In the bad old days of very high intensity airport X-rays, people did find fogging on their higher-speed films, but today's moderate or low-intensity scanners don't pose a threat to normal films. (Medical X-ray films aren't directly sensitive to X-rays either; a fluorescent plate is used to convert X-rays to visible light.) But I don't think it's just plastic that's protecting workers and bystanders; I think you'll find it's a plate of lead or other heavy metal. Sharkford 16:59, 4 January 2006 (UTC)

Possibility of X-ray goggles

By X-ray googles i don't mean goggles that emit X-ray's, which i know is odd i simply refer to a (portable) device able to penetrate clothing (and no not just of beautiful yound women, security too!) and reveal an image we can see, is this possible without using harmful high energy waves, if not what alternatives are there which come close? (7121989 01:55, 4 January 2006 (UTC))

There are many devices that use infrared (heat) cameras. Many clothing items allow heat to pass through. Any item between the body and the clothing will then show up easily. There is a lot of concern about these because show the outline of the body beneath the clothing. Also, pubic hair blocks visible body heat, so it the outline is visible. In the United States, anything related to nudity must be forbidden. So, we won't have publicly advertised infrared security systems anytime soon. As for hidden infrared security systems, they are probably installed and used in many locations already.

Want to make your own? Get a camera with a cheap pickup. It will have an infrared filter to block the infrared light (that makes the picture fuzzy). Remove the filter that blocks infrared and replace it with one that blocks visible light. Presto - you have an infrared camera. Then, hang out at the pool (where clothing is designed to allow the most heat to pass through), get arrested for taking semi-nude photos, and try to explain that you are just trying to make security better. --Kainaw 02:29, 4 January 2006 (UTC)

Cheap CCD cameras are only sensetive to near infrared, and thus are only giving you a view of things that are slightly redder than red (it may see through some fabrics but only ones that pretty transparent to visable light). True heat cameras generally use expensive cooled CCDs. The cutting edge for this security scanning technology is Terahertz radiation. --Martyman-(talk) 07:07, 4 January 2006 (UTC)

That is accurate, but I think it needs to be put more simply. Infrared vision does not equal thermal vision, and unless all the babes are wearing several layers of "Congo Blue" filter gel (or if her body is, for some reason, hotter than 250 degrees C), you'll just get freaked out by how weird people look. Why would anyone want to make Geordi-LaForge-porn, anwyay? -Bethefawn 0206; 1.8.06

This was also asked at the miscellaneous ref desk. Please don't double post. DirkvdM 10:53, 5 January 2006 (UTC)

See Backscatter X-ray - it is effectively a "X-ray goggles". Samw 22:34, 6 January 2006 (UTC)

Help with heat!

Hello, I don't have a calorimetre and I need to find the specific heat of lemon juice and any kind of antacid! I can't calculate specific heat, so If anyone can help me by just telling me that would really help out!!! Thank you all so much! Aberforthbil1657

• Specific heat

Here's a sample equation:

Calculate the specific heat capacity of copper given that 204.75 J of energy raises the temperature of 15g :of copper from 25˚C to 60˚C.

q = m x Cg x (Tf - Ti)

q = 204.75 J

m = 15g

Ti = 25˚C

Tf = 60˚C

204.75 = 15 x Cg x (60 - 25)

204.75 = 15 x Cg x 35

204.75 = 525 x Cg

Cg = 204.75 ÷ 204.75 = 0.39 J˚C^-1 g^-1

Sorry, I can't do LaTeX.

Here's a short guide for the military , and Britannica's . Do you know how to do the experiment? -- Mac Davis ญƛ. 05:50, 4 January 2006 (UTC)

pain and screaming

What is the reason that people scream when subjected to intense pain? I understand the reasons for pain and its beneficial nature, but the reason as to why people scream when they hit their finger with a hammer, for instance, eludes me. Is there a reason?

--24.29.92.197 02:26, 4 January 2006 (UTC)

To enlist the assistance of other members of the tribe ("help, I'm being bitten by a lion") or to warn them of danger ("beware: I'm being bitten by a lion"). -- Finlay McWalter | Talk 02:30, 4 January 2006 (UTC)

Ever wonder if humans scream differently when wanting others to come help or wanting them to run away? --Kainaw 02:36, 4 January 2006 (UTC)

Or how about other animals? — Knowledge Seeker দ 06:18, 4 January 2006 (UTC)

Nah, we animals react in the same way in both cases, we're just programmed to scream, without thinking whether it is meant to attract others for help, or to warn them, or whether it is futile. Pigs/cows, etc. scream out loud in intense pain in slaughterhouses, and I guess humans will do the same, regardless of the fact that it's not going to make any difference. The screaming is not a result of a design, but it just happened that the mutants that screamed had better rate of survival in the natural selection process. And it's a reflex action, it doesn't involve thinking and decision making ("should I request help or should I warn?"). deeptrivia (talk) 06:29, 4 January 2006 (UTC)

Wouldn't say whether it is a reflex action: it is more like a subconscious thing. After all, it only seems that animals with some developed brain: jellyfish don't scream, for instance, nor do a lot of insects. Dinosaurs and reptiles, probably moan in pain or something, or maybe that's a cliché from watching Walking with Dinosaurs. Anyhow, it's probably not so much that screaming has an evolutionary function, than having a brain does. It's just a primitive, basic, quick and forceful way to communicate: I mean, after all, having a language, or developing spears and bow and arrows aren't really evolutionary features than advantages that developed due to the evolutionary feature of having a brain. Then again, perhaps I'm arguing semantics: but there is a difference. A brain is more flexible because it can think of new ways to communicate; and perhaps change communication: after all, you can suppress your scream, and convert it into a more effective way of communication, if possible. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 13:58, 7 January 2006 (UTC)

Also because screaming, through some mechanism that eludes me at present, helps stimulate the release of catecholamines (adrenaline/epinephrine etc) for the fight/flight reponse, and endorphines (the endogenous opioids) for pain relief. Mattopaedia 00:12, 8 January 2006 (UTC)

earth

i am working on a class project and i want to know how high u can jump on earth--66.38.206.223 02:39, 4 January 2006 (UTC)

Well, you're on Earth, why don't you try it and measure how high you can jump? You could also look at the records for the sport High jump. See also Jumping and Gravity. --Canley 02:59, 4 January 2006 (UTC)

How can she know how high you can jump on the Earth unless you tell her? deeptrivia (talk) 15:50, 4 January 2006 (UTC)

Why do you assume he/she is on Earth? The question only makes sense if he/she has never been to Earth, so doesn't know what 10 m/s gravity feels like. =P —Keenan Pepper 08:23, 4 January 2006 (UTC)

Doesn't the question specifically ask "how high u can jump on earth"? It all depends how you define how high you can jump. Is it the highest from the ground? Then high jump records are what you need to look for, specifically Javier_Sotomayor who has jumped higher than anyone. However, there is also the highest jump above ones head. It currently stands at 59cm. David D. (Talk) 08:30, 4 January 2006 (UTC)

source

The high jump as an international athetics event has a rule that the competitor must jump using only one foot. So these records don't tell the whole story: it may be possible to jump higher using both feet. Gdr 12:07, 4 January 2006 (UTC)

It is not possible to jump higher with two feet than one. In the high jump, the trailing leg is used to provide much of the upwards momentum during 'take off', converting the lateral momentum of the run up into vertical motion. Watch the way the trailing leg kicks during a Fosbury flop. It is nowhere near possible to jump higher using both feet. For one, you wouldn't be able to have a fluent run up, thus there'd be no momentum to convert into upwards motion. Proto t c 12:41, 4 January 2006 (UTC)

I assume Gdr is refering to the vertical jump test. It is described at the following link as below (note i am not sure how reliable this article is since they cite an incorrect world record for the high jump).

"The best measure of jumping ability one that does not depend on the jumper's height is the standing vertical jump. The individual stands facing a wall, and with arm extended and feet on the floor, makes a mark on the wall at the top of his or her reach. The person jumps vertically, making a second mark at the peak of the jump. The distance between these two marks measures the vertical leap. This is an accurate measure of leaping ability, as each part of the jumper's body rises the same distance. A typical athlete has a vertical leap of 1 1/2 to 2 feet; the best male jumpers attain heights of 3 1/2 to 4 feet."

The claimed maximum height for the vertical jump is 4 ft (I could not find a verifiable wordl record) and equates to reaching a maximum height of 122 cm. This is quite a bit lower than Sotomayors 143 cm world record high jump. David D. (Talk) 00:08, 5 January 2006 (UTC)

What is a hepatitis a?

See the search box on the left of the screen? Try searching for "hepatitis" and see what turns up. --Robert Merkel 02:53, 4 January 2006 (UTC)

Solutions

If I have a solution with several components such as milk, water, and ammonia, how can I find the specific heat of the solution? I know the specific heat of the individual reactants but I don't know how to determine the specific heat of the overall solution. If anyone knows please list in J/g degrees celsius, Thanks! johnbog456

If a chemical reaction is involved, then I guess it's not really possible to get the sp. heat of the products from that of reactants. deeptrivia (talk) 03:24, 4 January 2006 (UTC)

As long as there is no chemical reaction (ammonia and milk might react; not sure) The specific heat of a mixture is the sum of (the specific heat of each part * the proportion of the mass of each part). Post again if that doesn't make sense to you. (found at http://www.carnicom.com/drought1.htm )

There seems to have been lots of similar questions lately. --AySz88^-^ 05:44, 4 January 2006 (UTC)

Yeah, that's right. Basically heat capacity (mass*sp. heat)is additive. So, (m1+m2)*C = m1*c1+m2*c2, where C is the sp. heat of the overall soln.deeptrivia (talk) 05:51, 4 January 2006 (UTC)

Cracking a Linux box

I half don't expect and answer to this or I'm afraid I already know the answer. Can I crack the root password on a Linux box without root access? I set one up several months ago and it has been sitting on my network contently doing nothing. Today when I tried to log in as root I found I'd forgotten my password. I tried all the various combinations I might have used to no avail. I still have a regular user but that's about worthless. It's running slakware 9.0 and I've upgraded the kernel to 9.4.22. I figure I might be able to make a boot/root floppy set and run setup. Will that work? Can I do the same from an iso image CD. I'd start searching Google, but I've gotten spoiled by Misplaced Pages's reference desk. It's not as fast but I don't have to choose from sixteen gizzilion possibilities. Thanks.--◀Puck▶ 04:48, 4 January 2006 (UTC)

Try booting with init=/bin/sh in the kernel command line. —Keenan Pepper 07:33, 4 January 2006 (UTC)

I'm going to try that with an ISO CD, but I was kind of hoping to do it remotely. I don't have a keyboard or monitor attached and I don't really want to have to lug one into the other room. If I have to go through all that I may just wax the whole thing and put the slakware distro on it, assuming that will even work on a p133. Thanks.--◀Puck▶ 07:54, 4 January 2006 (UTC)

Hmm, remotely. Let's think about that. If you can get root access without a password remotely, then anyone can, right? =P The reason why the init=/bin/sh thing isn't a security hole is because you need physical access to the box. —Keenan Pepper 08:17, 4 January 2006 (UTC)

That was kind of what I meant by I'm afraid I already know the answer. Security bites at times.--◀Puck▶ 08:55, 4 January 2006 (UTC)

Others mentioned local root exploits. If it's been several months and you haven't accessed the machine to apply patches, there is probably a local root exploit you could use to gain access. Basically go to http://www.securityfocus.com/vulnerabilities, pull down linux and kernel or your specific distribution and look for the local root exploits. They're not just going to show you how to do it, so if you didn't already know how to use an exploit you're not going to be able to easily. Better solution is to go get physical access and use a livecd as others mentioned. - Taxman 18:13, 6 January 2006 (UTC)

Boot from a rescue CD which gives you write access to the boot partition with root access. If you don't have a suitable CD, then take out the hard disk and mount it in another Linux box. On a Linux box where you know the root password, look at /etc/passwd or /etc/shadow (depending on your configuration) and note the encrypted version of your password there. Then edit the passwd or shadow file on the disk of the system you've forgotten the password for. You now have a known password on that system.-gadfium 08:06, 4 January 2006 (UTC)

I think the slackware install CD will give write access, if not I know I've got knopix around here somewhere. I do have another box where I know the root password. So what you're saying is if I edit /etc/shadow on the box I'm locked out of so that root has the same hash as the box I can get into that should fix it? That makes sense if I'm understanding you right.--◀Puck▶ 08:55, 4 January 2006 (UTC)

One other thought: are you trying to login as root at the console? It is likely to be forbidden from remote sessions. It's easy to mistake this symptom as "forgotten password". Notinasnaid 10:25, 4 January 2006 (UTC)

I vaguely recall that when remote root is disabled you get an message saying so. I rarely disable remote root becuase the boxes are inaccessable to the outside world unless you can get through two NAT boxes. Anyway, I'm logged in as my regular user and trying to su. I've most definitely forgotten the password.--◀Puck▶ 10:37, 4 January 2006 (UTC)

For completeness, if the box is running old software for which there are local root exploits, you could use that root exploit to get root and reset the password. Note that if you can exploit it, so can anybody else with shell access to the box (or can use a remote exploit to execute that command as an unprivileged user), so fix the hole after you use it. --Robert Merkel 12:54, 5 January 2006 (UTC)

Forgot my user password on Windows XP Professional

On my desktop, I forgot my user password, and the hint word doesn't make any sense to me any more. How can I get into my account again? deeptrivia (talk) 05:22, 4 January 2006 (UTC)

Take it to a computer repair place, and tell them. That's the easiest way. -- User:Mac Davis

Yeah, it is, but if you have to do it often, such as when supporting people who can't understand how to use ntpasswd, using it works like a charm every time. It's probably what the guys at the repair place will use. I just wish I had the same thing for my Linux box.--◀Puck▶ 07:47, 4 January 2006 (UTC)

For Linux, just stick in a Knoppix CD, mount your normal root partition and edit /etc/shadow under it. The install CD for your distro probably also works, you just need to get into a shell somehow (try Ctrl-Alt-F2). —Ilmari Karonen (talk) 12:42, 4 January 2006 (UTC)

Thanks, that was informative. I'll check ntpasswd out! deeptrivia (talk) 22:31, 4 January 2006 (UTC)

Movement of the Earth

Earth has a bit of information under the subheading Earth in the solar system and there is also some information at Planetary orbit.--Ali K 07:57, 4 January 2006 (UTC)

And don't forget precession. StuRat 22:46, 4 January 2006 (UTC)

seeking widest possible concensus

I'm seeking a concensus on the subject of mergers at eumetazoa. TheLimbicOne(talk) 14:46, 4 January 2006 (UTC)

shadows caused by albedo

I was wondering if there is a specific term for the shadow created from a reflective body such as the moon. In a sense, we know something is a shadow from a "direct" source of light whether it be natural(the sun) or artificial(a light bulb) but as far as these producing the light to something else and then this specific body reflecting the light: shouldn't there be a different term?

Your input would be much appreciated. I've been pondering this thought for some time now.

Sincerely,

Christopher Cole Chardon, Ohio

Now you've done it. I'm going to have "Moonshadow" playing in my head all day. Well, at least it's not "My Sharona". --Trovatore 15:47, 4 January 2006 (UTC)

It took me a long time to understand the question, but I suppose you simply mean "What should one call a shadow that is cast by reflected light?" I don't see why there should be a different term and anyway, most light we see is reflected. Consider what what shadows would be like if the Sun's light weren't reflected all over the place by the atmosphere (or whatever). They would be totally absolutely completely pitchblack. Most of the light around us is reflected light. And I imagine that light that is created in the Sun gets reflected many times there, too, so even our main source of light is mostly reflection (don'\t know this, just seems plausible). DirkvdM 11:03, 5 January 2006 (UTC)

RHEUMATOID ARTHRITIS CURE

(no text in body of question)

• Please read the instructions at the top of the page and try again. - Mgm| 19:09, 4 January 2006 (UTC)

• I don't believe there is a cure, just ways to treat it. Aspirin, for example, relieves pain and reduces associated swelling. StuRat 22:40, 4 January 2006 (UTC)

element lead

what is the melting point of the element lead?

• I added a few square brackets to your question. Does that help? —Ilmari Karonen (talk) 22:24, 4 January 2006 (UTC)

(If you're confused, that means "click on the lead link".) --AySz88^-^ 04:34, 5 January 2006 (UTC)

amphibians

...are animals that live in the water and on land. What else would you like to know? -User:Lommer | 22:52, 4 January 2006 (UTC)

Energy Conservation 2

If a virtual particle appears in a vacuum, hits another particle, losing energy, and bounces off into it antiparticle, then then wouldn't energy conservation be violated because it has lost some of the borrowed energy? Thanks 216.209.153.49 23:24, 4 January 2006 (UTC) Max

If you look above, to here, the question has already been answered. GeeJo _{(t) (c)} • 23:43, 4 January 2006 (UTC)

It's the same guy. -lethe 23:47, 4 January 2006 (UTC)

I answered above. -lethe 01:45, 5 January 2006 (UTC)

Universal IDs

Greetings:

I'm trying to find material relating to the concept of "Universal ID", which, in my case, is defined using the following scenario:

" A group of government officials and information managers at major corporations who point out that the proliferation of single-use identifying keys for individuals is causing major inefficiency, embarrassing and costly cases of mistaken identity, and considerable waste of time and money. They propose a single lifetime ID for every Canadian resident that would be used for everything from tax returns to grocery check-cashing cards."

And I have to argue along the lines of:

"a universal ID would lead to loss of privacy and essential freedoms, and would be open to considerable abuse."

I would highly appreciate any pointers to wikipedia entries, books, journal articles, web site materials pertaining to "universal ID" in the above sense.

Regards,

129.97.252.63 23:30, 4 January 2006 (UTC)

I believe Identity card is what youre looking for, but I don't think it examines the Canadian case in great detail. GeeJo _{(t) (c)} • 23:45, 4 January 2006 (UTC)

I'm not sure how much they've written about this topic in particular, but the folks at the would certainly have something opposing it. Similarly, you might want to search . --George 14:27, 5 January 2006 (UTC)

January 5

Lungs

How do the lungs Work?

Perhaps you didn't realize this is an encyclopedia. Have you tried looking up lung? -- Rick Block (talk) 00:24, 5 January 2006 (UTC)

Oxygen Planet

Ok, in theory if i took a planet the size of earth same atmospherical structure but 100% oxygen consistency, landed on this planet (with a suit) and lighted a match, would the planet exploded? I have been told 'No' by various sources, why not?

And as another interesting point when I light a match on Earth why doesn't 20% or so of the earth atmosphere explode? (7121989 00:50, 5 January 2006 (UTC))

Oxygen alone isn't an optimal fuel for an explosion. Oxygen atoms will combine with other oxygen atoms to create 0₂. When you heat up the O₂ to break it apart and force it to combine with another oxygen atom, you don't get much heat surplus. Now, if you use a molecule that is a little unstable, provide it with something it wants (usually oxygen), and then add heat to give it a nudge, the molecule will break, release a lot of heat, and the halves will combine with the oxygen. So, all in all, you really need fuel, heat, and oxygen to get something good going. Consider going to a planet that has an atmosphere of well mixed 50% oxygen and 50% methane - then light a match. Of course, I doubt you'd ever get the chance since some flaming meteorite will beat you to it. --Kainaw 00:59, 5 January 2006 (UTC)

Of course the planet's surface might also be flammable, but then the same would apply - a meteor would probably have beaten you to it. Other than that there are two (potential) fuel sources. First there is the match, which will burn up incredibly fast - you'll see small 'poof' and then nothing. The second source is you. Better make that a very non-combustible suit or the little 'poof' will be followed by a somewhat bigger one... DirkvdM 11:11, 5 January 2006 (UTC)

Of course, the heat of atmospheric entry would have blown the entire place up even if a meteor hadn't wandered along yet. 198.62.217.2 13:11, 6 January 2006 (UTC)

Or lightning. Eek. Bethefawn 2206, 6.1.06

A new form of fire?

What other examples are there of fire, in the sense of rather than rapid oxidisation, an exothermic reaction with another element or compound?

With these examples could one make a new type of more efficient combustion which can remain more prolonged?

Or, just came up with this the other extreme, cold fire, an rapid endothermic reaction which emits cold as it sucks in lights and sinks to the ground like a really cold dark heavy smoke, is it possible to be created? (7121989 00:50, 5 January 2006 (UTC))

Similar to the question above, your question is limited to oxygen combustion. There is nuclear fusion and fission also - neither of which requires oxygen and both are capable of being prolonged for very long times. However, I cannot think of any chain reaction that absorbs energy. You might try to call a black hole a chain reaction that absorbs energy, but I'd say you are being very liberal with the idea of a chain reaction. --Kainaw 01:01, 5 January 2006 (UTC)

There really can't be any other form, since that is the definition of fire. An endothermic reaction like your "cold fire" is not self sustaining and won't have the power to suck in light, something that only black holes can do. Matter can absorb light or heat that hits it directly, but won't "suck it in." There's no such thing as emitting cold, since cold is a lack of heat. An endothermic reaction like the one inside a chemical cold pack will absorb heat from the environment, but it won't necessarily be dark, nor will it exist in the form of smoke or have a particular density. Night Gyr 01:10, 5 January 2006 (UTC)

Rust is oxidation of iron. Is it exothermic? User:Zoe| 16:41, 5 January 2006 (UTC)

I believe it is, but it happens at such a slow rate that the temperature difference generated is negligable. -User:Lommer | 17:58, 5 January 2006 (UTC)

Yes, and reversing rusting is endothermic - I can't remember the chemical, but I did it in chemistry class and the beaker happened to turn cold. I can't remember if it was an acid (most likely not, because it simply just allows it to slide off, it doesn't reverse the reaction as more just excise the rusted parts). Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 10:11, 8 January 2006 (UTC)

Most expensive chemical element and compund

What is the most expensive chemical element and compound by market price currently? and i have also heard ridiculous prices on antimatter, but has it ever been made, surely none exists now? (7121989 01:34, 5 January 2006 (UTC))

Bear in mind, the most expensive elements are all only available in very, very small quantities, usually as the result of high-energy collisions in particle accelerators, and aren't feasibly producable in reasonable quantities. As such, any cost-figure attached to elements are simply scaled up from the cost per atom. Because of this, any element of about 110+ is going to be hideously, mind-bogglingly expensive. As for antimatter, yep, it's been produced. It's used in PET scans among other things, though again, only on the order of a relative handful of particles. GeeJo _{(t) (c)} • 04:11, 5 January 2006 (UTC)

What's the most expensive stable element? Common Man 03:04, 6 January 2006 (UTC)

Cesium, probably. Of course, "stable" can be a tad subjective (of course, I'm just playing with semantics here) - protons eventually do decay. ;-) Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 20:01, 7 January 2006 (UTC)

lizard regeneration

Is it possible for a new lizard to grow from a piece of tail broken off an original? I know that it can grow a new tail if it loses one, but can one grow from the piece that has fallen off?

Salamanders are better than lizards at leg regeneration. The "fallen off piece" does not grow a new salamander. For an up-to-the-minute review of limb regeneration and how some of our new understanding may be applied to human organ regeneration, see this week's issue of Science: alteripse 02:19, 5 January 2006 (UTC)

While lizards can't do that, note that planaria, a type of flatworm, can do so. StuRat 10:26, 5 January 2006 (UTC)

Also, the Crown-of-Thorns starfish, a major blight on Australian reefs, can do this. The method of population control used was to hack them to bits and throw the bits into the ocean, an unfortunately each of the little bits grew into a new starfish, increasing the numbers dramatically. smurrayinchester 15:43, 5 January 2006 (UTC)

The secret of regeneration in general is in the cells' genetic programming: they have to learn to recognise certain chemical signals in order to grow again, trigerring off a complex biochemical pathway (as it does in germination), or develop into a new stage (often they are all intermediary) - often mature, specialised cells in humans can't do that, either that, or we don't know the signals yet. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 10:14, 8 January 2006 (UTC)

Some trees can also do that trick. You can grow a willow tree from a larger willow branch. – b_jonas 15:52, 8 January 2006 (UTC)

Earths location

Lets say the Earth was 1 foot closer to the sun as it is now...how much would that affect the climate here in Earth?— Preceding unsigned comment added by 68.117.16.64 (talk • contribs) 2006-01-05 05:32:13 (UTC)

None.--◀Puck▶ 05:47, 5 January 2006 (UTC)

Go outside and stand in the sun. Then get a stool and stand on that a foot higher. Any difference? The Earth's orbit wobbles a bit and has been speculated to cause changes in climate, e.g. the ice ages, but that's likely to be more than a foot. enochlau (talk) 05:51, 5 January 2006 (UTC)

Interesting question. The Earths orbit is elliptical so as it goes round the sun at certain times of the year it is closer than at other times. The 1 foot you mention is a trivial difference. At its closest distance to the sun, perihelion, the Earth is 147 million km from the Sun. At its greatest distance, aphelion, it is 152 million km from the Sun. So there is a difference during the year of approximately 5 million km. The Earth is closest to the Sun in July January and furthest away in January July. David D. (Talk) 05:52, 5 January 2006 (UTC)

Actually this year Earth was at closest, perihelion, on Jan 4 (yesterday), it will be farthermost away, aphelion, July 3.USNO Data.--◀Puck▶ 06:07, 5 January 2006 (UTC)

To demonstrate how insignificant this difference would be, let's do some calculations. The amount of light which hits the Earth from the Sun is inversely proportional to the square of the distance. Since the average distance is around 93 million miles, this is about 491 billion feet. The difference in the squares of 491 billion feet and 490,999,999,999 feet is about 0.0000000004%, so it would change the Earth's temp by about that percentage. This would work out to around 0.000000002 degrees F. These calcs are very approximate, but give some idea of how insignificant the change would be. StuRat 10:06, 5 January 2006 (UTC)

Of course the Earth's orbital period would have to decrease too, but even if there is an exponential relation between the two (how do they relate again?) then that would also be too minute a change.

But how much would the distance have to change for it to have any effect? And suppose global warming would really get out of control, could we use nuclear explosions (like in the tv series Space: 1999) to achieve this? And while we're at it, alter the rotational period too, so we get 100 or 1000 days per year, so timekeeping can be made nice and decimal too. :) DirkvdM 11:33, 5 January 2006 (UTC)

About the relations, I suspect you would need to use some elliptic equations in order to replot the new orbit after you've pushed it in by one foot. ;-) Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 10:17, 8 January 2006 (UTC)

Use nukes to move the earth? No, no ... no. All of about 0% of an explosions energy (no matter how big) affects the momentum of the planet. The most effective way to move the planet would be to sling HUGE amounts of matter in the opposite direction, at high speed. A Moon-sized chunk should get you a few percent further out from the Sun, if you could get it faster than ~11km/s (escape velocity). And then you'd have to make sure its orbit won't ever intersect the Earth's new orbit, or KaPOW! Tzarius 23:09, 5 January 2006 (UTC)

In case one is wondering how the Earth can be closer to the Sun in winter, the answer is that the effect of Earth's axial tilt completely overwhelms any difference made by the varying distance. Plus, it's summer south of the equator. -- Cyrius|✎ 07:51, 6 January 2006 (UTC)

Which would mean that the differences between summer and winter would be much greater in the southern hemisphere if it weren't for the fact that it's mostly ocean, which has a stabilising effect. I think. DirkvdM 10:07, 7 January 2006 (UTC)

How to copy/paste wikipedia articles including images

To make a long story short, I would like to be able to copy and paste entire wikipedia articles (including text and images) onto my usb drive so that I can take those articles and view them on a different (offline) computer. When I select everything on a wikipedia article and copy and paste it into a microsoft word document, all I get is text, no images. If I individually select the pictures and copy/paste them it works fine, but that would take an extremely long time. How can I do this efficiently? (Please note that I have no intention whatsoever of using this for any illegal or immoral reasons) Flea110 06:53, 5 January 2006 (UTC)

If you're using IE, have you tried File --> Save As... ? The resulting files are somewhat messy and inefficient, but it might work, and it's fast and easy. --AySz88^-^ 06:59, 5 January 2006 (UTC)

I'm actually using firefox, and I just tried using the 'save page as' function. I saved the page to the desktop, and when I opened that file (still on the first computer), the page was a little garbled (but certainly readable) and the pictures showed up fine. When I transferred the file to the offline computer, the text showed up fine, but the where the images should have been there were little red "x"s in the corners, and it displayed the text name of each image. Can anyone think of anything else? (thanks for trying, aysz88) Flea110 07:13, 5 January 2006 (UTC)

That's because IE bundles the html file, the css file (if present), the image files, and possibly other used files into one file on your harddrive (a .mht file, multipart html file). So when you copy it to the other computer, everything works fine. Firefox, unfortunately, DOESN'T do it. It puts all files except the HTML file in a separate folder next to the HTML file. If you want to transfer it to another computer after that you'll have to copy both the HTML file and the folder. It's a pity really - the MHT feature is one of the few REALLY GOOD features of IE, I think. There seems to be a Firefox extension to fix the problem and add the feature to FF though, but I haven't tested it. TERdON 21:52, 5 January 2006 (UTC)

I actually just received the answer to this question from a friend via msn messenger. In case anybody else is wondering, here's how it's done. File--> Save As, (be sure 'web page, complete' is selected) and save it DIRECTLY to the usb drive. It works fine then. aysz88, you were right after all, but my mistake at the time was not saving it DIRECTLY to the usb drive. Ahh.. Feels so good to solve a problem. Flea110 07:46, 5 January 2006 (UTC)

Glad you got the answer to your problem. :) --AySz88^-^ 07:56, 5 January 2006 (UTC)

An alternative would be to use HTTrack, a very powerful tool (so be careful what you do). It will not only download the page but also all the pages it links to. In case of Misplaced Pages this would download the whole site because everything is ultimately interlinked. Actually, without restraints, it would download the entire internet. To only get the pics you can limit the linkdepth to one and specify only image links (or something similar - I haven't used it for a long time). DirkvdM 11:45, 5 January 2006 (UTC)

astrology

Is the prediction by astrology correct? Is the basis of astrology is firm?

Answer to first question is sometimes. Answer to second is no. David D. (Talk) 07:09, 5 January 2006 (UTC)

The predictions seem correct because typically a horoscope contains four or five vague "predictions" (You will meet a stranger, you will face challenges today). According to probability, at least one of these should come true in some way, and since people want to believe the horoscope, they will see minor coincidences as fulfillment of the prophecy. smurrayinchester 08:16, 5 January 2006 (UTC)

Let's define our terms here. Without necessarily wanting to add credence to astrology, there is a huge difference between the "astrology" advice columns in the daily newspapers which use Sun signs only, that apply to 1/12 of the entire population; and a serious natal chart drawn and interpreted by a professional astrologer that uses an individual's precise birth data and which applies to that person alone. The latter is astrology (whether you think it has any validity or not), the former is not. JackofOz 08:33, 5 January 2006 (UTC)

And I stand by my answer above. Smurrayinchester is correct when he says that people want to see it work and will shoe horn the predictions into known events or cherry pick their character traits to fit. For those with a less cynical view I suspect it is often self fulfilling (obviously this is a POV comment). In this sense it may be comforting and even positive with regard to ones life. David D. (Talk) 08:41, 5 January 2006 (UTC)

I wouldn't dispute any of that. I'm just saying that, mostly, what people think of as "astrology" is a misnomer, it's something that has virtually no relevance to true astrology at all. JackofOz 08:51, 5 January 2006 (UTC)

Oh, maybe it was not clear, i agree with your comments. May be I am missing this too. I thought the astrologers were all about prediciting character and to a certain extent fate. Certainly I would not call the daily horoscopes astrology, although i thought they did 'pretend' to make some similar statements but there is just no method i.e. fiction David D. (Talk) 09:00, 5 January 2006 (UTC)

Also note that the "theory" behind astrology, if it can be called that, is based on the actions of Greek and Roman gods. If you don't believe in Roman gods, like Mars/Ares, you shouldn't believe that people born when Mars is visible will have the traits of that god (combative, for example). There is a basic incompatibility in believing in Christianity or any other modern religion and also believing in astrology. There is also a basic incompatibility in believing in science and astrology. StuRat 10:22, 5 January 2006 (UTC)

This is not true at all. Astrology was never so limited and many Christians (and scientists) were astrologers throughout the early modern period. Our history of astrology does a fairly good job of outlining that. A belief in astrology does not necessitate a belief in Roman or Greek mythology, it simply requires the believe that "heavenly bodies" could have influences on individual people. The place where astrology and Christianity usually butted heads was the issue of free will, not in gods. --Fastfission 03:12, 6 January 2006 (UTC)

See Forer effect. --Robert Merkel 12:47, 5 January 2006 (UTC)

dandruff

how to cure dandruff

Read the article Dandruff. There's a section on Treatment. --Canley 09:10, 5 January 2006 (UTC)

agriculture

How can science help agricultutre?--~~how science can help agriculture?--219.94.50.118 10:37, 5 January 2006 (UTC)

Is this, by any chance, homework? Notinasnaid 11:37, 5 January 2006 (UTC)

Must be a very important question, because (s)he asks it twice. DirkvdM 11:47, 5 January 2006 (UTC)

Here's a hint to start you off when you do your own homework: agricultural science. --Robert Merkel 12:48, 5 January 2006 (UTC)

computers

what is an operating system? who is considered the father of modern computers?

See Operating system. As for the father of modern computers, depends on what you call a modern computer and whether you're thinking about hardware or software. Blaise Pascal and Charles Babbage constructed mechanical computers. Ada Lovelace is said to be the first programmer (in which it would be a 'mother' - you male chauvinist pig :) ). If by 'modern computer' you mean the use of transistors then it could be Julius Edgar Lilienfeld (funny, I thought the transistor was a British invention 'stolen' by the Japanese). If you mean the third generation computers, with integrated circuits, then it would be Jack Kilby. See also History of computing hardware. DirkvdM 12:06, 5 January 2006 (UTC)

Some other luminaries include Alan Turing, who in large part founded computer science, Claude Shannon, who developed digital circuits, J. Presper Eckhart and John William Mauchly for the ENIAC and the design of the stored program computer, John von Neumann for writing up Eckhart and Mauchly's work and circulating it, and Konrad Zuse, for apparently doing most of this independently in Germany before the collapse of Nazi Germany interrupted his work. But the modern computer was the product of many people developing a lot of technologies and figuring out how to combine them, working in collaboration and sometimes in competition, and it's simply impossible to assign one person credit for it all. --Robert Merkel 12:43, 5 January 2006 (UTC)

Thus I have read: "The Atanasoff-Berry Computer was the world's first electronic digital computer. It was built by John Vincent Atanasoff and Clifford Berry at Iowa State University during 1937-42." This would be without transitors. Tubes and/or relays , I guess. see http://www.cs.iastate.edu/jva/jva-archive.shtml John Atanasoff --GangofOne 00:55, 6 January 2006 (UTC)

Yes, you can Atanasoff to the list, but the ABC wasn't a modern "computer" as we would understand it. It was a major development that pioneered a number of key features of modern computers, but it was a special-purpose machine as distinct from the later ENIAC and the von Neumann machines that followed it. --Robert Merkel 03:46, 6 January 2006 (UTC)

Pure copper 3,000 yrs ago

What procedure would people in the bronze age have used to produce pure copper from copper oxide?

From about 5000BC, smelting, usually charcoal-fuelled, was used to process the ores into pure copper. GeeJo _{(t) (c)} • 13:52, 5 January 2006 (UTC)

Particle accelerators

Hi just wondring if anyone could help me on this. How has the UNILAC accelerator been used to increase our knowledge about chemical elements? How does the technique work and how does it rely on an understanding of the structure of atoms? Thanks

Why is science such important in our daily life?

See the articles UNILAC, Linear particle accelerator and Science. --Canley 22:12, 5 January 2006 (UTC)

Eye Strain

Is it possible to strain your eyes by reading or watching tv with little or almost no light? It is an old wive's tale that I would like to know the rationality and/or proof behind. Any help will be greatly appreciated! -- Chloe

How Stuff Works has a pretty good explanation on the subject. GeeJo _{(t) (c)} • 14:06, 5 January 2006 (UTC)

Thanks! That was very helpful! any other sources are still greatly appreciated. -- Chloe

That article was about reading in low light. Reading is done at close range, which means it requires your eyes' focusing muscles to work harder. (Unfortunately, the article "Accommodation (eye)" is a stub.) Watching TV, you're not sitting so close to the screen, so this is less of an issue. (And at a movie theater you're even farther from the screen and your eyes are practically focused at infinity, so being in the dark matters even less.) -- Anonymous, 21:20 UTC, January 5.

Also, the brightness on the TV should be adjusted to match the brightness of the room. A dim TV in a bright room causes as much eye strain as a bright TV in a dim room. StuRat 22:13, 5 January 2006 (UTC)

Speed of a horse

How fast can the average horse run? --163.153.132.5 14:42, 5 January 2006 (UTC)

For a sprint (100 yards)? Or for miles? Notinasnaid 16:15, 5 January 2006 (UTC)

I don't know much about horses, but the fastest horse in the Melbourne Cup last year ran 3200 m (10 500 ft) in 3m 19 sec. That's an average speed of 58 km/h (36 mi/h). Average horses must be a bit slower than that.--Commander Keane 23:15, 5 January 2006 (UTC)

According to a quick google search(animals speed):

• A normal 'quarter horse' can run 47.50mph (top speed) for a quarter mile
• A ridden horse can go 40mph
• The distance record for a horse may be 100 miles in 9 hours

Also, it turns out lots of people use the exact same chart of animal speeds. Black Carrot 02:56, 7 January 2006 (UTC)

I've read in a book that a gallopping horse goes 43 km/h. – b_jonas 15:45, 8 January 2006 (UTC)

Teaching myself Geology

I am teaching myself geology for a course and i am looking through some old exams, some help please i am lost on this q. What name is given to the process which causes surface layer rock to break off? --15:33, 5 January 2006 (UTC)

I don't believe you; you're eroding people's patience. Proto t c 15:48, 5 January 2006 (UTC)

I believe we can weather it. Weathering = breaking up of rock into smaller particles. Erosion = movement of those particles from one area to another. This should be in even the most basic geology/Earth science texts. TheSPY 15:59, 5 January 2006 (UTC)TheSPY

erasables( computer storage devices)

RAM / ROM ? Tzarius 22:49, 5 January 2006 (UTC)

Or WOM of course :) GeeJo _{(t) (c)} • 02:28, 6 January 2006 (UTC)

astatine

How many protrons does the element Astatine have? How many nuetrons does the element Astatine have? Thank you Amy T207.118.208.184 23:37, 5 January 2006 (UTC)

From Astatine: The atomic number gives you the number of protons in an atom; in this case it's 85. The atomic mass gives you the total number of protons and neutrons; in this case it's 210. To find the number of neutrons, subtract 85 from 210. Sometimes there are many common isotopes of the element, in which case the number of neutrons would vary; in this case, it looks like there's only one common isotope. enochlau (talk) 23:41, 5 January 2006 (UTC)

How many electrons does the element astatine have? Thank you Amy T207.118.208.184 23:50, 5 January 2006 (UTC)

As many as it has protons. (Unless it's ionized, in which case it may have more or less.) —Ilmari Karonen (talk) 01:37, 6 January 2006 (UTC)

January 6

Size of internet, size of wikipedia

If you were able to download the entire internet, how much space would it take up on a (rediculously massive) hard drive? How about if you were able to download all of wikipedia? Flea110 01:13, 6 January 2006 (UTC)

Don't know about the entire Internet, but for Misplaced Pages, see Misplaced Pages:Database download. —Ilmari Karonen (talk) 01:34, 6 January 2006 (UTC)

I thought wikipedia was the whole thing. -lethe 02:28, 6 January 2006 (UTC)

Wow, it's mindboggling! deeptrivia (talk) 02:34, 6 January 2006 (UTC)

The Internet Archive Wayback Machine is about 1 petabyte in size and is growing at a rate or 20 terabytes a month according to its FAQ (compaired to a mere 40 gigs for a wikipedia database dump). The Wayback is presumably larger than the internet because it includes multiple versions of each site. Then again, because its all accessable online its really part of the internet itself, making the actual size of the internet somewhat larger. If you were to include the size of all such caches, including search engine indexes, not to mention material available through filesharing networks and Bittorent, and twenty-some years of newsgroups, the number quickly becomes astronomically large.

Or for a more succinct response, a quick googling yields this.... Jasongetsdown 03:22, 6 January 2006 (UTC)

Since 1 GB of hard disk space costs about half a € storing Misplaced Pages would cost about 8 €. Storing the Internet would however cost half a million €. DirkvdM 08:13, 6 January 2006 (UTC)

New Scientist found a website which offered the entire web for download at 22.2877482 petabytes, or 23 931 287 382 megabytes . Trying to download it however resulted in "Insufficient memory on drive C: for the internet. Insert disc in drive A". smurrayinchester 17:02, 6 January 2006 (UTC)

LOL. DirkvdM 10:11, 7 January 2006 (UTC)

Don't forget that the internet is much bigger than just the web. While the web may have lots of web sites and images on it, the internet at any moment has a whole lot of other bytes flying around, including emails, IMs, P2P traffic, etc. That is to say that the more-static web is a tiny fraction of the more-dynamic internet. I recall hearing an ISP study that showed that WWW (web) traffic was actually less than 20% of their traffic. --Quasipalm 19:41, 6 January 2006 (UTC)

And of course you couldn't (or else shouldn't :) ) download other people's emails. DirkvdM 10:11, 7 January 2006 (UTC)

Digital cable to DVD Recorder

Can i hook a Wireless Transmitter to my Digital Cable and then hook my wireless receiver to my DVD recorder to record things from Digital Cable?

Generally, no, because digital TV is always encrypted to stop people accessing channels they do not pay for. This has the side effect that you can't get the raw digital video feed out of the set top box. See Television encryption for more details on this. You can attach a TiVo type device to a digital TV box because it uses an analog interlink. So, you could build a device that takes an analog signal from your digital cable box, re-encodes it as a compressed digital video stream, sends it to a computer which has a DVD burner in it, and then burn it to that. But this would be quite a significant feat of DIY home engineering ;) If you want to record programs from your digital cable box, a PVR like TiVo is still the best way to do it, alternatively I think some home DVD recorder devices can be connected directly to your box like VCR tape recorders could be. Hope that helps -- Anonymous Guy

NSAIDs for dogs

My dog is taking an NSAID called carprofen (no article yet). Why shouldn't dogs take human NSAIDs like aspirin or ibuprofen? Why shouldn't people take carprofen? —Keenan Pepper 02:57, 6 January 2006 (UTC)

All I can tell you is what a Google search turns up, so take it with a grain of salt. Carprofen has apparently gone through some human trials in Europe, but was never put on the market for economic reasons. Dogs can be given aspirin, but the toxic doses are relatively low and ulcers are likely. Veterinary aspirin is available. Ibuprofen causes stomach ulcers far more readily in dogs than in humans. -- Cyrius|✎ 07:46, 6 January 2006 (UTC)

Free circuit simulator software

I'm looking for a compreensive circuit simulator that can manage things like spark gaps, flyback transformers, an arbitrary number of inductive couplings, etc. I found a nifty one in Java but it doesn't support flyback circuits, and the controls are rather annoying to deal with. The program I'm looking should run on Windows XP.

Anyone knows of such a thing? ☢ Ҡieff⌇↯ 03:49, 6 January 2006 (UTC)

blogs

Blogs? Wouldn't that be better on the humanities reference desk? ☢ Ҡieff⌇↯

Would my ISP be able to know what websites I visit

Would my ISP be able to know what websites I visit? I am in a very small town and there are only two companies offering services here. One ia a big telecom company which I at present use. But, the other company is a new, small and a local company which has given some 50 connections in my town. I plan to move to the small ISP because it is cheap. But, I am afraid whether they would be able to see what websites I visit. Can anyone please tell me? Do you have any other advice or tips?

• Yes, they could, but they probably won't unless you get involved in something which would result in the police requesting the information from them. If they got a website, try reading their Privacy Policy. If I remember correctly, employees are not allowed to look up such info unless there's good reason to. - 131.211.210.11 08:24, 6 January 2006 (UTC)
• Your ISP can potentially see everything you do (except when visiting secure web sites, where they can see where you go, but not what you type). Your e-mails too. In some places they may be allowed to record this information. In some places they may be required to do this, in case the police later want to investigate something. The solution is to not visit illegal sites, I guess. Notinasnaid 10:14, 6 January 2006 (UTC)

• on a side note visiting certian websites will probably get you put on an FBI watchlist, doesn't take much these days, certianly wikipedia users are all on such a list, very subversive website, grounds for concern--172.174.71.47 14:25, 6 January 2006 (UTC)

• Heck using the phrase 'FBI watchlist' on the internet is probably enough to get you on such a list--172.174.71.47 14:26, 6 January 2006 (UTC)

• We've got our Eye on you. And you. - Taxman 16:36, 6 January 2006 (UTC)

How do you know if a site is 'illegal' before you visit it? And whose law determines what is illegal on an international medium? DirkvdM 10:19, 7 January 2006 (UTC)

You could also get an encrypted connection to a proxy service and use some sort of onion routing or freenet type thing from there. Not perfect, but does make it hard to tell where you are visiting. - Taxman 16:38, 6 January 2006 (UTC)

I would suggest Tor, being widely supported free / open software. No proprietary protocols or single business in control. Tzarius 06:07, 7 January 2006 (UTC)

These rules might also vary by nation. Depending on how you connect to the Internet, a bunch of other people in addition to your ISP might know all about what you doing. Even though secured websites are protected from normal spying, they are not protected from keylogger spyware. User:AlMac| 07:06, 7 January 2006 (UTC)

About the privacy policy. Who guarantees that they stick to that? My ISP has the ability to follow my actions. Who has the ability to follow my ISP's actions? And would they be interrested in protecting my privacy (they'll probably be in the business of violating privacy themselves and without incentive thieves don't snitch on thieves, do they?) DirkvdM 10:19, 7 January 2006 (UTC)

Electrophysiology

I am an electronics engg student. My interest is to study about a subject that links electronics with biology or rather human physiology. Is it apt for me to do my higher studies in "ELECTROPHYSIOLOGY"? If yes plz let me know about the books i've to refer to and the universities in the U.S.A and the U.K. which offer this course. --210.214.157.86 09:01, 6 January 2006 (UTC)

UCAS, who have a list of all the courses available in the UK, don't recognise "Electrophysiology". However, they do have several courses for cybernetics: . Doubtless the US has similar. smurrayinchester 17:27, 6 January 2006 (UTC)

A quick read of our article on electrophysiology might also help. At UCLA we had an undergraduate program in biomedical engineering which sounds like it may be of interest to you. I'm sure there are other schools with similar degree programs as well . --David Iberri (talk) 22:12, 6 January 2006 (UTC)

aromol?

Can someone Please tell me what Aromol is? It is in Smith's Rosebud Salve and I want to know what it is? I have looked everwhere and can't find anything on it? So please someone help me, what is Aromol? Thanks

You could always try contacting the manufacturer and asking them. --Anonymous, 10:00 UTC, January 6, 2006

optics - experiment

how to make an achromatic doublet ? mail answer to :

It's pretty much summed up by this diagram:

Flint glass and crown glass can be replaced by any two materials with different dispersion. —Keenan Pepper 13:35, 6 January 2006 (UTC)

• Also, if you look at our chromatic aberration article, you will see how to calculate the focal lengths of each part of the lens you need, if you know some data about the materials. --Bob Mellish 16:11, 6 January 2006 (UTC)

viral/ infectious diseases

Are there any viruses, bacteria, etc., that live in the cold weather? I know that the cold weather just weakens the immune system and makes the body more succeptible to infection, but i was just wondering whether or not there are any viruses that actually just live in the cold environments and are strong enough to infect people. Thanks! ----- Eryn

Short answer: yes. Long answer is more complicated. There are bacteria and viruses that thrive in extreme environments: freezing and boiling hot environments, but these rarely affect (or infect) humans. Shall we assume that you are only interested in bacteria and viruses that can cause human disease and the degree of cold is the winter temperature range away from the poles where most of us live (like down to 10 degrees below water freezing)? Moderate freezing cold will kill many bacteria and some viruses, but the main effect of cold on bacteria is just to slow down reproduction and activity (which is why refrigeration retards bacterial growth). Bacteria and viruses vary greatly in their abilities to survive outside a host but the temperature is less of a factor in this than availability of water and food and absence of harmful substances like soap or high osmolality or intense sunlight. Dehydration will kill most bacteria faster than cold will, but some viruses can survive dehydration and some can survive indefinitely being frozen. Some pathogenic bacteria require direct person-to-person contact (e.g., bacteria of gonorrhea or the AIDS virus), but others (e.g., the spores of tetanus) can survive in the environment for long periods of time in various forms. For example, there has been concern about whether smallpox or influenza viruses can remain infectious in graves. The most recent example was the investigation a few years ago of 1919 flu victims buried in the permafrost of extreme northern arctic islands for 80 years. Precautions were taken to avoid releasing potentially infectious material. That said, I don't know of any cases of smallpox or plague or influenza known to have been contracted from graves or crypts. Cold weather does have an effect on transmissibility of respiratory viruses by affecting human behavior and perhaps altering mucous membrane defenses. Complex topic. alteripse 13:45, 6 January 2006 (UTC)

Thanks... I know this is a complicated question. You were very helpful. However, are there any specific instances in which entering a cold environment would promote the spread and possible contraction of a virus or bacteria into a human body? And if so, what are they???? ----- Eryn

Ah, this sounds simple, so I'll wade in. This site explains the #1 myth, ie. if you go outside 'You'll catch your death of cold!', which is usually uttered by an old lady in a Jane Austen novel. --Zeizmic 18:05, 6 January 2006 (UTC)

Thanks for your input. I think i worded my second question poorly though. Are there any bacteria, viruses, etc., that live only in the cold weather and are then contrsacted by humans or animals? For example, a virus taht lives and thrives outdoors in cool temperatures and then infects the first host that it encounters. possibly this bacteria/virus stayes dormant until contact with a host is made.... (Maybe this has been answered already in a previous reply and i just dont see it.) But if there is such a virus/bacteria, a name or description would be most helpful. Thanks! ----- Eryn

I asked our disease control doctor here (MUSC hospital). She said that there are many bacteria and viral-like lifeforms documented in the South Pole. In her opinion, it is heat that is harmful to them, not cold. They usually freeze and thaw well. They overheat and die easily - which is why running a fever is a good thing. --Kainaw 20:39, 6 January 2006 (UTC)

Physicists

Hi, I read in several places that the fundamental building block of the universe is information or events...I know how it sounds, but I haven't read it in new agey looney pages, I read it in like, news articles, and in some physics pages which I cannot remember,but I can't distinguish real science from far fetched claims...so, do you think this is true or somewhat true? because I am aware that the building blocks of matter are quarks and subatomic particles like gluons and stuff.

also, quite apart from that, here's this quote :We are now synergetically forced to conclude that all phenomena are metaphysical; wherefore, as many have long suspected — like it or not — 'life is but a dream.' - Buckminster Fuller. see? I mean, stuff like this... what do u think of what he says?, or am I taking it too litarally and he meant something else.--Cosmic girl 14:35, 6 January 2006 (UTC)

Comment: I think, apart from subtle philosophical difference, information in this context can mean energy of which matter is another manifestation, and events can mean time. Space is left out, but again, some people think space it no existence independent of matter. I find this statement a bit vague though. deeptrivia (talk) 16:02, 6 January 2006 (UTC)

Comment2: Well, I don't know the context, but he's probably referring to something related to the wave-particle duality and uncertainty principle. For more about the "life is a dream" proposition, see Advaita_Vedanta#Advaita_and_Science, Advaita_Vedanta#Three_levels_of_Truth, Advaita_Vedanta#Are_the_world_and_God_wholly_false.3F. deeptrivia (talk) 16:12, 6 January 2006 (UTC)

Thank u :), but what I actually meant to ask was if this notions are somewhat supported by current respectable science? or just by speculation, like eastern philosophies.--Cosmic girl 16:21, 6 January 2006 (UTC)

Yeah, this wasn't intended as a reply, just some comments. Advaita_Vedanta#Advaita_and_Science should give an idea though of how far physicists entertain these views. deeptrivia (talk)

I've seen similar scientific speculations, in particular in the book Information - The New Language of Science by Hans Christian von Bayer. As I understand it, the basic idea is to think about a hypothetical perfect theory of everything -- what if you knew all the equations governing reality at the lowest level, and had all the data about everything (knew the full quantum wavefunctions etc), then you could imagine the whole universe evolving as a computational process -- in other words, we don't need to assume any reality beyond the information process. What I got from Bayer's book is that physicists are finding applications for information theory in physics, so that the physical information encoded in a system of particles may in fact have real physical meaning. The traditional basic connection is between entropy in statistical physics and information theory. But I'm no expert on any of this - I can't tell if these physicists have simply confused their models with reality. 84.239.128.9 19:09, 6 January 2006 (UTC)

cool, so you mean that, information theory implies that nothing outside or besides the universe is required for the universe to exist? I mean, nothing besides the information and computations of our universe?... if so, how can it know that? I mean, can't the universe be like a big videogame? it can seem the only thing for us, but we can never know that which lies outside the computer that contains it ... maybe we can only know the software... it sounds really crazy and hard to understand, but i think that the information theory has space for a videogame conception of reality, or a simulation for that matter, but I know nothing about physicists, so I need the expert's opinion. --Cosmic girl 19:30, 6 January 2006 (UTC)

The expert is just another character in the video game. But anyway, take a look at Edward Fredkin, Steven Wolfram; they attempt to show reality is a large computation in some machine. GangofOne 03:04, 7 January 2006 (UTC)

I really suck at math and physics, but I believe that if everything is quantizied ( I'm sure I spelled that wrong :S )if everything is, I think the universe is no diferent than a videogame... but then, if it is, we can't know much about philosphy since the physics of the real universe (the one outside) aren't known to us...and maybe are even irrational to our brain...but that would surely signify there is a trickster God ...or a kid out there, haha --Cosmic girl 16:52, 7 January 2006 (UTC)

You should really check out interesting things like physical information and quantum entanglement. Information represents order: it can affect energy almost take on physical properties because of the laws of thermodynamics about things tending towards disorder. For example, destroying information in a hard drive, or in a computer processor, will result in a rise of entropy and therefore heat. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 20:25, 7 January 2006 (UTC)

who are the five google billionaires?

who are the five google billionaires?

Omid Kordestani, David Drummond, Shriram Kavitark Ram, Sergey Brin and Jonathan Rosenberg --Quasipalm 19:30, 6 January 2006 (UTC)

A query regarding Pepper Pad

Have anyone of you used a Pepper pad? I am just interested in buying a pepper pad, but want to know this- I heard that its resolution is 800x600.

I just want to know how would a 8.4" screen placed horizontally compare with a screen placed vertically with respect to size. Would the 8.4" Pepper pad be equialant to a 15" CRT monitor in 800x600 resolution or would it be equivalent like viewing a 14" CRT screen? Or would it be equivalent to viewing some other screen with someother resolution? Can you please tell me the equivalents?

Can we view full page in a Pepper pad without sideways scrolling?

Thanks for making me look that up That was really interesting! This seems to be the legendary Linux PDA that everybody has said will come one day. The resolution is good enough to get in most web pages without scrolling (just set your computer to this and see!). The specs look good, but you really need to get some independent reviews. Never be the first on the block! I find the info a bit misleading, since they seem to be marketing to the 'ipod' generation, with all sorts of promises, like browsing in your car. This thing only has Wifi which has a raft of access problems. There is no such thing as free broadband wireless (which is what they seem to be implying). My Blackberry costs $100 a month, for very slow Internet access. --Zeizmic 18:18, 6 January 2006 (UTC)

how does the cable car work?

Depending what you mean by cable car, see the links on this page. smurrayinchester 16:54, 6 January 2006 (UTC)

Is the pen mightier than the keyboard and mouse?

Which one do you feel is better of the following. A touchscreen pen? or a mouse with keyboard? Which do you think is the easier, and which one do you prefer if given a choice?

Personally, I'd go for the mouse and keyboard. Sum0 17:57, 6 January 2006 (UTC)

Habit. I began using a keyboard in 1978. I didn't use a mouse until about 1992. So, to this day, I am more comfortable with a keyboard for 90% of my tasks and a mouse for simply moving windows around. If I were to have started with a mouse, I would probably use the mouse more. If I had started with a touchscreen pen, I'd probably use the touchscreen pen more. If I had started with a neural implant, I'd probably use the neural implant more. --Kainaw 19:30, 6 January 2006 (UTC)

The touchscreen pen seems to have the disadvantage that the weight of your arm is not supported, as it is with a mouse. Thus, after hours of use, your arm will get tired. StuRat 20:47, 6 January 2006 (UTC)

It depends on the application. For regular computing like editing Misplaced Pages, writing emails, browsing the internet, etc. I'm comfortable with a mouse and keyboard combo. But at my work a keyboard would just clutter things, so a touch screen is preferred. Dismas| 22:14, 6 January 2006 (UTC)

I have a tablet PC... you can actually rest your arm on the screen with no problems, it's strong enough. For text entry, e.g. in my law lectures, I still find keyboard faster and more accurate. But in my maths lectures, I'll write with my stylus instead of writing on paper, because it's searchable. For other applications, I actually find that if there isn't much text entry (because handwriting is slow and inaccurate), using the stylus is far more natural, e.g. when casually browsing the net, or playing cards. enochlau (talk) 04:52, 7 January 2006 (UTC)

As said before, depends on the purpose. Generally, I prefer the keyboard over anything else (including the mouse) because it's easier on my mouse arm, much more versatile (try typing with a mouse :) )and much faster once you know the shortcuts (if any - which is the main reason I still prefer Photoshop over GIMP, even though that means rebooting to msWindows). I don't have a touchscreen but a tablet and I haven't gotten the hang of that yet, but that's a matter of what one's used to. I suppose it would be better for graphical stuff (using a mouse in a graphical application is the worst for my mouse-arm), but for quick notes and diagrams and such I still use old fashioned pen and paper. DirkvdM 12:02, 7 January 2006 (UTC)

how to teach newborn to swim?

Why would you want to? 198.62.217.2 17:37, 6 January 2006 (UTC)

This is actually common, 198. It can be a good idea for saftey reasons to introduce "swimming" at an early age. Read more here: --Quasipalm 19:25, 6 January 2006 (UTC)

My older sister almost drowned quite a few times as a toddler before she was finally taught to swim. It seems she simply didn't know any better and walked off piers or into the deep ends of pools. Since then me and my three other siblings were all taught to swim as infants. None of us had any near-drownings, and we all love the water. Seems like a good reason to me.

As the the how, I've only seen it done in special classes. You usually first teach how to blow bubbles under water, and then when that comes naturally, you have one parent release the kid and another call them and they do the rest. — Laura Scudder ☎ 20:45, 6 January 2006 (UTC)

• Infants are surprisingly good at swimming in an controlled environment (after all they have been swimming for 9 months before). All you need to do is make sure they know to close their mouth and not breath for a little time, while underwater. Liz Barker's baby Dexter went to a swimming class long before he turned 1. - Mgm| 11:22, 8 January 2006 (UTC)

Los Angeles-class submarine mast pattern

Does anyone know the story behind the giraffe-like black-and-white pattern on the masts of this photograph of a surfaced Los Angeles-class submarine? (In case that link doesn't work, it's the sixth picture on this page. Sum0 17:56, 6 January 2006 (UTC)

I can't find an answer either, but if I had to guess, it's probably camouflage for when the sub is running just under the surface with its masts extended. -- Cyrius|✎ 02:54, 7 January 2006 (UTC)

deepest part on the planet

what is the deepest part on the planet below sea level?

The Mariana Trench Black Carrot 18:31, 6 January 2006 (UTC)

Challenger Deep is the exact point. deeptrivia (talk) 01:03, 8 January 2006 (UTC)

Earth's core. DirkvdM 12:04, 7 January 2006 (UTC)

Finding Research Papers Online

I'm working on a project for science fair, and having some trouble tracking down the earlier research papers my sources cite. Google doesn't turn anything up, and I don't know many good search sites. How do professional scientist find papers? Black Carrot 18:37, 6 January 2006 (UTC)

Try Google Scholar rather than just Google. Also, if you leave near a University or College, just pop in the library and ask what journals you should search. Most major universities have free access to journals as long as you're on a campus computer. Good luck. --Quasipalm 19:18, 6 January 2006 (UTC)

Thanks. That's a start, but it doesn't have the papers I'm looking for, probably because they're a bit obscure and outside the mainstream. I'm using my project to test Rupert Sheldrake's experiments with 'the sense of being stared at'. Any other suggestions? Black Carrot 20:28, 6 January 2006 (UTC)

There is a psychology database similar to Medline and I think it includes parapsychology research. It will be available through most college or university libraries. Ask a librarian for help. The best starting point is often a paper that you do have, because the librarian can see how it is catalogued in the database and can then help you look for older but similar papers. There are a couple of American universities that have supported "paranormal" research, usually in association with the psychology dept, often under the name of parapsychology. You could call one of those depts and ask a secretary if a faculty member would be willing to talk to you once for an "interview to help with a school science project" and you might get lucky enough to get a few minutes of time. If so, ask their opinion of the research in that area and ask for suggestions on how to most efficiently find published research on the topic. They may be able to suggest specific journals, search terms or even authors to look for. Good luck. alteripse 20:53, 6 January 2006 (UTC)

You may also go directly to Rupert Sheldrake's books. He may describe his research there, or at least point you to more information in the notes. However, you may have trouble since often these sorts of pseudoscience authors take great care to hide their research from scrutiny. --Quasipalm 20:57, 6 January 2006 (UTC)

If your campus is subscribed, you'll also be able to use http://www.sciencedirect.com and http://www.engineeringvillage2.org. deeptrivia (talk) 23:35, 6 January 2006 (UTC)

You should check if your school or local library (etc.) subscribes to databases such as Thomson Gale Group or EBSCO host; These sites contain digital copies of articles from various scientific journals, some of which may be found as a hard copy in your library. If you live in a state such as Pennsylvania that has something similar to the AcessPA system, you can get access to these databases free with a library card. --Dragoon235 04:17, 7 January 2006 (UTC)

inventing a source of perpetual energy

How close are mankind from inventing a source of perpetual energy?

As close as we always were. As far as anyone knows, it's prohibited by the laws of physics. -- SCZenz 18:41, 6 January 2006 (UTC)

With one exception. The universe is believed to obey the law of conservation of energy. Therefore, the universe has a universal constant supply of energy. It never loses or gains any. It is just perpetually there. --Kainaw 19:27, 6 January 2006 (UTC)

It's a closed system, though. Doesn't count. Tzarius 06:13, 7 January 2006 (UTC)

Though that doesnt stop people from trying. History of perpetual motion machines shows the various attempts at creating one. GeeJo _{(t) (c)} • 19:37, 6 January 2006 (UTC)

Of course, there are many energy sources that will last for billions of years, so are as good as perpetual, like hydro, solar, tidal, wave, wind, and geothermal energy. And while each chunk of fuel for a nuclear reactor may only last a few years, there is enough nuclear fuel to power the world virtually forever. Renewable sources, like wood, are also good forever if properly managed. Only fossil fuels will be "used up" someday soon, perhaps decades or centuries, that's not certain. StuRat 20:40, 6 January 2006 (UTC)

What if we were to figure out how to accelerate the transition from bio-waste into crude oil? Then, fossil fuels would also be a renewable energy source. We could keep pumping out those greenhouse gasses until we need a huge umbrella to cut down on solar heat. --Kainaw 20:46, 6 January 2006 (UTC)

Well, you definitely can get methane from bacterial action on waste products, but I call this a "biofuel", not a "fossil fuel", to show it's source isn't "fossils". I don't know of any way to generate crude oil or coal from current waste products using bacteria, but I don't see why you would want to, as those forms both require refining and pollution controls while methane is ready to burn as is. StuRat 23:00, 6 January 2006 (UTC)

It's a bit more abstract, but the questioner might like to read Conservation of energy which states that energy is never created or destroyed, but is a constant. However, the Second law of thermodynamics states that the energy of an isolated system, while constant, is in a constant process of equalling out, meaning that the contained energy becomes more and more difficult to obtain in a general sense. --Quasipalm 20:52, 6 January 2006 (UTC)

While energy can theoretically be changed into mass according to ${\displaystyle E=mc^{2}}$, this doesn't appear to happen anywhere on Earth. Energy seems to end up in the least usable form, which is heat. While usable energy can be generated from a heat differential, as in the case of geothermal energy, constant temperature heat is not a usable form of energy. StuRat 22:52, 6 January 2006 (UTC)

Conversions from mass to energy do happen on Earth, but on a small scale; see Binding energy for example - in nuclear fusion/fission. enochlau (talk) 04:55, 7 January 2006 (UTC)

Have to disagree. ${\displaystyle E=mc^{2}}$ is true always and everywhere, in every energy transition. It tells the equivalence of mass and energy. What it doesn't tell you is how to do it, or even if there is a way to do it, just that IF you do it, this is what you get. If I burn a gram of gasoline I get 42 kilojoules. I compare the mass of the oxygen and gasoline that went in and the CO2 and H2O that came out, the numbers of atoms are exactly equal, but the products have a mass 4.6e-13 kg less than the reactants. 42 kJ = 4.6e-13 kg c^2 Just because 4.6e-13kg is too small for you to measure conveniently doesn't mean it isn't happening. -- GangofOne 07:08, 7 January 2006 (UTC)

I'm not quite sure what you mean. In combustion, the energy is not achieved through ${\displaystyle E=mc^{2}}$; it comes from the formation of bonds in the CO₂ and H₂O. smurrayinchester 09:47, 7 January 2006 (UTC)

You say, in combustion the energy comes from the energy difference in the broken bonds and the reformed bonds, true, but it is still true that the rest masses of the reactants is greater than the rest masses of the products, and that mass difference is equal to the energy produced divided by c^2, regardless of the fact that this wasn't mentioned in chemistry class (because the mass is too small to measure). I encourage you to not let go of this question, ask around wikipedia, ask at Wikipedia_talk:WikiProject_Physics . I will explain more if asked. One thing to think about: In a nuclear reaction, (which I assume you accept as an E=mc^2 process), it's the same thing-- breaking of one bond and forming others (except it's bonds of the strong force, whereas in chemistry it's electromagnetic forces.) GangofOne 12:57, 7 January 2006 (UTC)

Yes, chemical bonds affect mass, if I recall correctly. For example, the quarks that make up atomic nuclei are pretty light: it's the gluons that carry the nuclear forces and result in the sheer mass of the nucleus. The more stable something is, the less energy it needs in its bonds to make it stable, and therefore it weighs lighter than its component parts in a less stable state.

If you don't mean 'eternal' too literally, the Sun. Almost all other energy sources are derivatives of solar energy. Plants get their energy from the Sun and animals from the plants, so all biofuel is solar energy. Fossil fuels are dead plants. Wind is caused by uneven solar heating of the atmosphere. And hydro-energy comes from water evaporated by the Sun. The only exceptions I can think of are tidal energy (caused by planetary movement) and geothermal energy. And of course nuclear energy, but that's also the source of the Sun's energy. DirkvdM 12:14, 7 January 2006 (UTC)

Well, nuclear energy's source is ultimately Population III stars and Population II stars that formed before the sun - their immense mass would have formed the heavy metals like uranium et al in their dying stages. Which of course, some became unstable, resulting in fissionable material. Fission isn't the source of the sun's energy, anyway, but it was the product of stars. Geothermal energy (also aided by nuclear decay) is also due to star formation somewhat. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 09:39, 8 January 2006 (UTC)

As far as I know, there is research done with the ultimate purpose to make a power station operating on nuclear fusion. Such a power station would give much more energy cheaper than any energy source we currently have available. It would also eliminate the problem of digging nuclear waste as it doesn't produce any. So, in some sense, it would be "a source of perpetual energy" for some values of perpatual.

See fusion power and Timeline of nuclear fusion to see what state these researches are currently. – b_jonas 15:08, 8 January 2006 (UTC)

mining the moon

When mining the moon, what useful minerals would i find?

According to Moon, you will find uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium, aluminium and hydrogen. It doesn't state the quantities of each. --Kainaw 20:12, 6 January 2006 (UTC)

Also note that the cost of getting the minerals back to Earth would far exceed their value. StuRat 20:33, 6 January 2006 (UTC)

You're assuming that they actually want to get it down to the Earth though. If they have a mining operation in place, then with just a bit more money (What's a few billion more?) they could refine the minerals there and start a sustainable colony. Dismas| 00:16, 7 January 2006 (UTC)

Then they would need to get oxygen and water (not to mention a smelting plant) up to the colony on the moon, which would be just as prohibitively expensive. StuRat 00:45, 7 January 2006 (UTC)

Supposedly the most valuable thing (probably the only economically exportable good) to mine on the Moon is Helium-3.--Pharos 05:09, 7 January 2006 (UTC)

Well, till we get a space elevator, that is. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 20:27, 7 January 2006 (UTC)

Even so, the thing that makes mining practical on Earth is that geological (and sometimes biological) processes create local concentrations of useful materials that far exceed the global levels. The moon is geologically and biologically dead; as I understand it that moon rock is pretty much the same everywhere upon the moon. The only things worth mining (except for helium-3) might be any asteroids that have crashed into the moon - however, it might be easier in the future just to mine the asteroids in the asteroid belt directly.

Why does a pendulum work?

(no question)

A mass at one end the pendulum is pulled downard by gravity. It accelerates, but it redirected by a pivot point so that the momentum is going back upward. Gravity then pulls it down again. This repeats. A pendulum will eventually stop due to air resistance, friction in the rotation joint, and so on. By adding energy (like the big weights in a grandfather clock), you can keep a pendulum going. For more, see pendulum. --Kainaw 20:44, 6 January 2006 (UTC)

The characteristic of a pendulum which makes it ideal for time-keeping is that the period (amount of time for it to complete one full swing) is constant, even as the magnitude (distance of the full swing) reduces due to air resistance and friction. Thus, a pendulum can be used to measure time until it comes to a complete stop. StuRat 22:45, 6 January 2006 (UTC)

I've always had trouble buying that. It seems like, if it takes a certain amount of time to get, say, from out horizontally to pointing at the floor (multiply by 4 for period), it will take less time to get from lower than horizontal to the floor. --Black Carrot 04:32, 7 January 2006 (UTC)

The Black Carrot is right to be suspicious; it's not actually quite true. (See the pendulum article for a look at the math, but it's not simple.) However, it is a very good approximation. If the pendulum starts out horizontally, its full weight is acting perpendicular to the string and this sets it in motion very fast. If it starts out near the bottom of the swing, its weight is almost parallel to the string, so the force on it is a lot less, and so is its speed. As it works out, the period is not exactly the same in the two cases, but it's very close to the same (especially for small angles).

Try it yourself. Take a ball of string and some tape. Unreel a few feet of string and tape the string to the ball where it comes off the ball. Tape the end of the string to the top of a doorframe. Set the ball to swinging just a couple of inches and time it for 10 swings back and forth. Then swing it up to a high angle, let it go, and time it again. I just did this and the times I got were between 19 and 20 seconds for 10 swings every time: my error in timing was probably larger than the difference between a long and a short swing. Of course, you will get different numbers according to how long you make the pendulum, but they will still agree with each other. (Because friction reduces the length of swing very fast with such a light pendulum, you might also try timing just 2 or 3 swings, but then the relative error of measurement is greater.)

In order for it to be accurately true that the period is fixed, the pendulum would have to follow a cycloidal path rather than a circular one: see tautochrone curve. However, this turns out not to be useful for practical clockmaking, because the mechanism necessary to do that introduces too much friction. Instead, pendulum clocks were designed so that the drive mechanism would keep the angle of the swing relatively small, and as constant as possible. For the really accurate pendulum clocks that astronomers used before electronics superseded them, very long pendulums were were used (like say 10 feet), but they would swing a very short distance (just a few inches).

--Anonymous, 05:45 UTC, January 7, 2006

Fooling credit score calculators

Is there any truth in Jaron Lanier's claim that people can and do arrange their finances in bizarre ways in order to get an improved credit score? ~~ N (t/c) 21:19, 6 January 2006 (UTC)

The rules seem to be sufficiently bizarre that such opportunities would present themselves. For example, a similarly bizarre policy by airlines of charging more for a one-way trip than the corresponding round-trip led to the technique of buying a round-trip ticket and only using the first half. StuRat 02:04, 7 January 2006 (UTC)

Neural Net Image Categorization

Most of the information I can find on neural nets is either very basic and general, or owned by a company and unavailable to outsiders. Where can I find information on the construction of neural nets that leans towards the conceptual (I only know Java, and don't have time to decipher other languages) and towards a large number of inputs, say on the order of millions? Black Carrot 21:46, 6 January 2006 (UTC)

I hope you realize such a neural net will require massive computing power to run at a reasonable speed. Also, what is the application ? Fluid dynamics ? StuRat 22:38, 6 January 2006 (UTC)

I do realize that it will take some work to apply it the way I'm hoping to, but I don't think it's impossible, and I'm certainly willing to try. There are worse ways to waste time. I especially hope to find ways, as you mention, to reduce the number of inputs to a more manageable level, but I don't think I can go below the tens of thousands. I'm trying to find a way to search the web for actual images. Google is great, but it only does keyword searches, and I would like to be able to do more than that. I'd like something that can sepearate a set of pictures into a Yes pile and a No pile accurately, such as Tree v Not Tree. Naturally, neural nets lept to mind. The structures I've found so far, however, don't lend themselves well to this. It's not that they can't be set to sort into the right piles, it's that you have to have the piles sorted in the first place for backpropagation to work, and then the setup is fairly rigid, not dealing well with cases outside its specific expertise, and not dealing too well with new cases being added. The ideal search, though, would involve a progressive narrowing down, and would anticipate related cases. I've come up with some things I haven't seen anyone write about that I think would help, but I think things would go a lot faster if I could find out what the people who've been working on this for years have thought of. Any suggestions are appreciated. Black Carrot 01:04, 7 January 2006 (UTC)

Wow, that's quite an ambitious project. It sounds like the problems you are having are quite similar to those for voice recognition software. Specifically, the software can recognize the difference between "circumvent" and "circumnavigate" if programmed specifically for that task and adjusted for a given voice, but does a poor job of identifying a random word in a random voice. Also, such software needs to "learn" differences between similar words, which requires a great deal of user input to "train" it. I'm not even sure how you would define which picture is a tree and which is not, considering cases like a tree and a person, a tree branch, a tree sprout, a bush, a flower, etc.

I have thought of a much less ambitious search method, which could search for copies of an exact picture, possibly with a different scale. This could compare number of pixels of each color and look for a given ratio, as well as looking for colors to be in the same relative position on the pic. Complications such as mirror images, pics trimmed differently, non-uniform scaling, and different color balances would require quite a bit of coding to solve, but does seem doable. I've often found a pic via a web search which is just what I want as far as subject, but is too small. I would like a way to search for a full sized copy of the pic, even if the page doesn't contain the keywords I used in the initial picture search. Is that a project which would interest you ? StuRat 01:31, 7 January 2006 (UTC)

'Fraid not. I would expect that to be one of the functions of what I'm going for, but it's not by itself what I want. Besides, how many duplicate pictures are there floating around?

You see the problem pretty clearly. What I think I have to go for is something that, in its structure, mimics the way we see things. Not that it mimics the brain, that would be a waste of time and I don't have the background anyway. Here's how I see it. The integer inputs(from 0-255 in Java), form a massively multidimensional graph, at each point of which the output(a real number, ideally either 0 or 1) can be represented by a color, either red or blue, with black or white at the boundaries. Makes a nice, manageable picture, except for the countless thousands of unimaginable axes. I think 'phase space' is the technical name for things like this. Now, the most basic form of neural net (sans sigmoid) will draw a beautiful diagonal gradient, which is useless to me. A single-layer network that makes use of the sigmoid function will have a straight line(plane, hyperplane, however many dimensions) between one clear area of blue and one clear area of red, at any slant and position you want. Good start. A two-layer one will draw as many of those as you want(with colors strengthening each other where they overlap), then shove all the outputs above a certain value to one color, and all the ones below it to another, and you have a shape on the graph, most any basic shape you want. Great. Add another layer, and you can have a bunch of shapes scattered across the graph, making it nice and flexible. Now, within those shapes the output will be 0(No), and beyond them it will be 1(Yes), or vice versa, and you can clearly see which pictures(which points) will be accepted and which will be rejected. Dandy. Except that that's not what the graph needs to look like to mimic the trends in the positions of actual images. It's hard to say exactly what it would look like, but I can get the concepts down and let the program take care of the rest. A few characteristics of the goal graph: area around image points, axis-parallel lines out from points, perpendicular rotation of shape about origin, image point shadows, threads between points, and quite a few others I haven't nailed down. I've solved the first one. The idea there is that, for any clear picture, there is some amount of error or static you can add to each pixel and still keep the picture essentially and recognizably what it is. On the graph, this means that there is a certain distance out you can go in any direction (direction=one color of one pixel in the image, or movement parallel to an axis) or combination of directions from the point that represents the clear image, and still be in essentially the same place. So, if that point is one color, the area around it must be as well, but not the area beyond that. It's possible to draw a nice simple square/box/hypercube around that area with a two-level bit of neural net, but with the number of sides needed(two per axis, >80000 axes), that box is prohibitively expensive in terms of how many nodes the net contains. I eventually worked out that if, instead of multiplying each input by a weight, then summing them and running them through the sigmoid, you add a bias to each input, square each result, then do all the rest, it draws a nice little resizable egg of whichever color around any point you want, with one layer, startlingly few nodes, and the added benefit that the list of the biases, laid out in a rectangle, is the clear picture you started with. So, that's where I'm coming from. Any suggestions? --Black Carrot 03:59, 7 January 2006 (UTC)

Wow, you've really given this a lot of thought, I'm impressed. I still think the number of calculations necessary to search all of Google for all pictures of trees would take way too long to be practical for a search at present, but perhaps it would be good to have the technology ready and waiting for when such computing capacity comes along. Of course, just like voice recognition, I doubt if once you have the program optimized to find trees if it will be any good at finding, say, birds, until you alter the program significantly, then the same for every other object it needs to recognize.

I think some of the steps necessary for this to work might be valuable in and of themselves, however. I listed one above, another that interests me is "reverse pixelization". That is, I would like to be able to take a bitmap of a line and a circle, say, and create a vector representation of the geometric elements. One application would be to take a low res picture and generate a higher res pic of the same thing. Edge recognition is one aspect of any such program, that might be mentioned under machine vision.

Well, as I say, I'm quite skeptical that you will get the full program to work anytime soon, but still think it is valuable for it's side benefits. And, if you can write and sell such a program, I'm sure it would be worth millions! StuRat 06:14, 7 January 2006 (UTC)

I have done this before. The approach outlined is feasible, but I think you need to make your project a bit more well defined before you will be able to achieve much. It seems that you know what you need to look for, but to really get your project up and running, I would suggest that you simplify the problem first before proceeding. Try this: take a 8 by 8 grid, and see if you can create a neural network which can distinguish the characters A, O and E written on the grid in a pixelated form. Also, for your tree recognition scheme, you may want to consider alternative measures of classification which do not rely on the network of sigmoidal functions. There are plenty of quality papers on complexity analysis, image processing which will be handy. You may also want to search for imaging journals which deal specifically with diagnosis and such - many image processing/recognition algorithms are well established and used in the medical field. --HappyCamper 06:23, 7 January 2006 (UTC)

I definitely agree with starting with small, simple tasks and working your way up. Then again, this approach is recommended for any complex problem. StuRat 07:29, 7 January 2006 (UTC)

You might wanna look into Military Image Recognition Systems. --Jvh, 7 January 2006

Neural nets are (amoungst other, equivilent descriptions) a statistics object. It might be worth persuing them from that angle, particularly if you're looking for rigourus descriptions. Also, with the resoulution upscaling, there's a lot of work on statistics applied to images that would be useful background reading. Syntax 22:42, 7 January 2006 (UTC)

StuRat- I don't see why a well-designed system would take any more processing than what they already do, which is substantial in itself. Actually running something once through a net doesn't take much, and training it isn't that different from running something through it a few thousand times, so although I wouldn't be able to set it up on my laptop, I think the technology to do so is already sitting in Google's basement. Also, what I was talking about above is a system for describing the entire theoretical graph of all images in existence. Once I've got some idea of how that would work(like the example above), an idea of what mathematical and computational structure it would take to efficiently seperate all recognizable images from the near infinity of static surrounding them(and it is near infinity, try calculating the area of the graph), I'm pretty sure any net I base on it will work for all search terms. If you meant, once I'd done a search on trees it would be hard to move it to something else, that's no problem. I expect to start with a blank net each time I run a search anyway. I believe software is available that turns pictures into collections of vectors, if you're looking for it. My brother is into art, and his pad does that. As to the selling- I hope so, but I kind of like the idea of providing it for free. Also, according to the google searches I've been doing for hints on how to build nets, there are companies that are already marketing things a lot like this, and I'm not interested in competing for business.

HappyCamper- What do you mean by 'done this before'? Which bit? Professionally, or as a hobby? And what about the outline is feasible? What's undefined about it? Is it important to use A, O and E specicifically, or any set of letters? Or all letters? Using specific drawings of them, or a range of styles? What papers or how-tos, specifically, would you recommend, and how do I get to them?

Jvh- I wouldn't think they'd be sharing any of that information, but if you know how I can get it, I'd love to learn it.

Syntax- ???

Also, six clarifying statements, which I think should be more common in long discussions: I would prefer to use just neural nets, I don't care about the complexities of optimization until I have something up and running, I (as a highschooler) don't have access to anything and don't have experience finding it, I'm pretty sure going below 150x150 pixels would radically change the structure of what I'm doing (how we recognize things begins to change at that level) which means anything that works at 8x8 has limited application except as general practice, I support general practice as a way of getting an intuitive grasp of a system and have been doing it for quite a while already, and I don't care about most of the things the papers I can get to are about, like facial recognition and 3D recognition, just making a reliable searching tool.

One further question: does anyone know how to take a y=1/x graph and get a higher-dimensional version of it? I've decided I can combine two functions(area around image points, axis-parallel lines out from points) by taking each point that represents a clear image, and drawing curves asymptotically out in all axial directions. With three inputs(axes,dimensions), this would resemble six cones attached to the corners of an octahedron. With two inputs, this would resemble the graphs y=1/x and y=-1/x combined, meaning that if I made a two-input, two-level, three-node net out of the formulae O1= I1*12, O2= -I1*I2, and O3= O1+O2, or more accurately, O1= sig(B1+W1*((I1-B2)*(I2-B3))), O2= sig(B1-W1((I1-B2)*(I2-B3))), and O3= sig(-W3(O1+O2-.5)), where W means weight and B means bias, I would have what I wanted. This has proved difficult to extend to three inputs, and beyond. Another I need, beside the one above, is another way of taking 1/x to higher dimensions, three planes perpendicular to each other with curves asympotically approaching them, which would resemble a cube with all six corners carved out.

I appreciate all the help. --Black Carrot 23:06, 7 January 2006 (UTC)

BTW, since this is getting pretty long, should we move it to my talk page? --Black Carrot 23:13, 7 January 2006 (UTC)

can normal people get atum bombe?

using household stuff

No, not unless you keep enriched uranium and plutonium in the cupboard next to the enriched flour. If so, you need to be extra careful when baking bread. StuRat 00:02, 7 January 2006 (UTC)

See Radioactive Boy Scout Dismas| 00:04, 7 January 2006 (UTC)

January 7

Penis

Is it average for a 14 year old to have a 6 3/4 inch long penis and have 4 inches gurth?

That depends on if you are looking at a naked 14 year old girl at the time. StuRat 00:10, 7 January 2006 (UTC)

Studies on penis size are generally done on adults. So you probably will not find a study anywhere that gives averages for teenagers. Although, according to the Human penis size article, you're off to a good start. Dismas| 00:12, 7 January 2006 (UTC)

I second the above. I'm very familiar with the research on human penis size, and there has never been any research on 14 year olds (for obvious reasons). That said, let me warn you that there has never been high-quality research done on human penis size, regardless of age - it's just not a practical undertaking. The best we can say, given the limits of our current research, is that the average American penis is between 5 and 7 inches. So you're doing fine. --George 05:18, 7 January 2006 (UTC)

You are not as familiar as you think you are. I put a reference to such a study on the talk page of that very article last year at someone's request; it is still there. alteripse 01:42, 8 January 2006 (UTC)

"Very familiar" ? As the measurer or the measuree ? LOL StuRat 07:14, 7 January 2006 (UTC)

Alas, it's mostly an academic familiarity at this point. But I'm always seeking volunteers... --George 00:48, 8 January 2006 (UTC)

Wow, wikipedia really does have everything. Check out Penis#Size. It says, "the human penis is larger than that of the common chimpanzee, both proportional to body size and in absolute terms; one study has found that the average human penis is 5 inches (12.7 cm) in length when fully engorged with blood during arousal." No source though. --Quasipalm 15:53, 7 January 2006 (UTC)

exactly why would anyone like to know this subject???????

Penis data envy ? StuRat 18:45, 7 January 2006 (UTC)

Who was that? Black Carrot 23:17, 7 January 2006 (UTC)

Ethanol as fuel

If the U.S. capitalizes on the ethanol gas, how much do you think gas would go down? How much would Americans be saving?

Cars can run up to about 25% ethanol with conventional engines, which would make some difference, but not too much, on a global scale, especially since 10% ethanol is already used in many areas. On the other hand, if car engines were retooled to use 99% ethanol (with 1% gasoline in a special tank for cold weather starting), then that would have quite a significant impact on world petroleum consumption and thus prices. Unfortunately, ethanol prices would likely skyrocket, at least until production caught up with demand. A mixture of technologies, like ethanol, diesel, electric, hydrogen fuel cell, and compressed natural gas, is likely to avoid the type of supply shocks we get when solely dependent on one type of fuel. For example, if a family owns a gasoline car and an ethanol car, they could switch which one they drive dependent on the relative prices of each. This price elasticity would cause price stability, unlike the current inelastic price curve for gasoline, which causes price instability. Flexible fuel vehicles are thus ideal for managing prices. StuRat 00:16, 7 January 2006 (UTC)

Pay close attention to Brazil. They are in the middle of an attempted transition between petrol and ethanol. There are problems. Many of them appear to be solved. --Kainaw 00:35, 7 January 2006 (UTC)

However, Brazil has warmer weather than the US, so doesn't need the same alternate cold-weather gasoline starting tank. StuRat 00:38, 7 January 2006 (UTC)

Or, you could just provide better insulation for the tank. Gasoline would probably be cut down into a "backup" fuel source should the temperature dip below 13 degrees Celsius. The thing about ethanol is at least it's renewable: you can just keep on growing sugarcane or glucose-producing plants. I mean heck, someone could probably invent some new process to convert cellulose into ethanol. I guess the alcoholic beverage industry would probably boom with this, perhaps. (This reminds me that someone could possibly make a joke about ethanol as fuel, and "drunk" driving. Heh heh.) Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 12:45, 7 January 2006 (UTC)

The problem isn't that ethanol freezes in the tank, but rather that when it evaporates in the carbuerator it lowers the temp too much, which causes moisture in the air to ice up and block the carb. After it has been running for a while, engine heat can be used to counter this tendency. But, using gasoline until the engine reaches operating temp is a good fix until then. StuRat 17:08, 7 January 2006 (UTC)

I was thinking more about the flash point (since ethanol freezes at negative 114 degrees Celsius and freezing isn't so much of a concern anyhow), but then you just reminded me what a great coolant ethanol actually is. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 20:35, 7 January 2006 (UTC)

I wonder if the evaporative cooling of ethanol could be used to significantly cool the passenger compartment on hot days, prior to burning the ethanol in the engine. This would have the disadvantage that a broken heat exchanger could potentially spray ethanol into the passenger compartment (instead of the current antifreeze), so a more reliable heat exchanger design would be needed. Somehow I doubt if the cooling would be sufficient to replace A/C, but perhaps could help it out a bit. Alternatively, if used to cool the engine, perhaps a slightly smaller radiator would be needed. In the case of a tiny engine, perhaps air-cooling would be sufficient, like the old VW Beetle. This could improve fuel economy by eliminating the weight of a conventional liquid cooling system. StuRat 20:49, 7 January 2006 (UTC)

Two notes: Brazil has some very cold areas both in the mountains and in the deep south. So, it does have a problem with starting in cold weather. The common solution is a mini-gasoline tank for cold weather starting. As for why ethanol causes a problem. The boiling point of gasoline is 40°C and ethanol is 60-80°C (I'm going from memory, I'm sure the articles here have the specific temp). So, in cold weather, ethanol doesn't vaporize as well and liquid doesn't like to burn. --Kainaw 20:40, 7 January 2006 (UTC)

I would state it slightly differently, that vaporizing ethanol takes more energy, in the form of heat, than gasoline, so the temp drops more when it is vaporized in the carb, thus causing the icing mentioned previously. StuRat 20:56, 7 January 2006 (UTC)

computer display screen readability

Hello,

What makes some handheld computer and cell phone displays easier to read than others, both indoors and outside? If i was looking at a specification for different types of displays, what attributes contribute to readability the most?

thank you so much for answering my question!

--Linda

A backlight is very important, as is the text size, those should be in the specs. However, the contrast of the display relative to the background and the reflectivity and hardness of the glass or plastic bezel (and thus the resistance to scratches) is not something you are likely to see in the specs, so you should check each one out in person, if possible. One warning, don't fall for the stupid plastic film that "shows you" what it will look like when running, actually test it out. StuRat 00:26, 7 January 2006 (UTC)

I always have trouble pertaining to the subject at hand. I can never read what is on my laptop while i'm on the bus. I would also say that text size is important, but you may also want to keep your files private from peering eyes. i've also found that my laptop has had a clearer and brighter screen ever since i have gotten that new screen protector that is on television.

The vibrations from the bus will make it even more difficult to read. Hmmm, that sounds like something that could be improved, maybe with goggles with LCD screens inside them. That way, the screen would move in synch with your eyes. StuRat 20:36, 7 January 2006 (UTC)

internet? problem

hey i am really having a hard time. can you give me a website to find background information on linear dynamics? i've been working on it for 10 hours and can't find anything about background stuff. grateful for all help. --sami

Hi Sami. Have you seen Dynamical system#Linear dynamical systems already? --Quasipalm 03:55, 7 January 2006 (UTC)

pendullum

ON which principle does pendulum of clock work?I have a clock which has pendulum to show seconds measurement.It is not getting any energy from gear etc..but still it oscillates continuously.It is just placed on a pivot and after giving just slight push it gains its original motion with increased oscilations.How it doesn't loose energy by friction?

It does lose energy by friction, just very slowly. You will eventually need to push the pendulum again, unless it is one of those you also plug in. That type uses electricity to give the pendulum a little push with each swing. StuRat 07:11, 7 January 2006 (UTC)

It doesn't have to be electric. Wind-up pendulum clocks feed energy from the spring into the pendulum to keep it swinging. If you look closely, you will always find a mechanism that gives energy to the pendulum. --Heron 15:53, 7 January 2006 (UTC)

There's a fun desk toy that's based around a pendulum that never stops, and climbs back up to full swing if you reduce its arc. It uses a magnet in the weight and an electromagnet in the base that turns rhythmically on and off, or north and south, or something like that, based on an electric timer on a chip. Every time the pendulum swings near the base, it's given a little magnetic kick to keep it going. Of course, that would be a pretty pointless pendulum to use for a clock, since you could just hook the clock straight up to the chip and cut out the middleman. Apparently, people do it anyway, if StuRat is right. --Black Carrot 23:26, 7 January 2006 (UTC)

Yes, they do it because people like clocks that look traditional, but don't require winding, lifting weights, etc. If you think about it, the old rotating dial clocks are all quite silly and old-fashioned now that we have easier to read digital clocks, but many people still prefer those, too. StuRat 09:00, 8 January 2006 (UTC)

VIRUS

How would I go about to make a virus from normal pathogens and atoms that you would find in many house holds?

There are machines that can assemble short DNA strands from the amino acids, but I don't think they are yet to the point where they could build even a simple retrovirus, which is basically just DNA. To build a virus at present, you would start from an existing virus and alter it to have the desired characteristics. StuRat 07:06, 7 January 2006 (UTC)

It would be an interesting consequence of structural biology when we could start engineering retroviruses from scratch as biological weapons. Morbid, as well. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 13:50, 7 January 2006 (UTC)

Just to be pedantic, the Retroviridae are RNA viruses. That is, they have an RNA genome and require enzymes such as reverse transcriptase and integrase to convert their RNA to DNA and integrate it into the host cell genome, or use the host's transcription machinery to make viral proteins. The thing that eludes me is: Why don't retroviruses just start using host transciption to make viral proteins directly from their native RNA? Why not just bypass that whole reverse transcription thing? All I can think of is the extra transcription may allow for incresed genetic variability through spontaneous mutations (transcription errors), but I'm just guessing. Anyone else know? -- Mattopaedia 00:57, 8 January 2006 (UTC)

For one, not having its RNA converted to DNA would mean it couldn't incorporate into the host's genome and therefore wouldn't be replicated. --David Iberri (talk) 16:17, 8 January 2006 (UTC)

If you want to do it with household equipments, not a laboratory, I guess it's much easier to build a computer virus. – b_jonas 14:42, 8 January 2006 (UTC)

Eye sight question (dim light)

I know that reading and other nearwork may lead to myopia, but does darkness have anything to do with it? Say reading with a very little light, or using a computer late at night with no lights on? Thanks in advance. Gflores 07:11, 7 January 2006 (UTC)

I think I answered a very similar question earlier. It is important to have the room light match to light on or from the object you are viewing. That is, dim the lights when reading a dim computer screen, and brighten them when reading a bright computer screen. StuRat 07:18, 7 January 2006 (UTC)

The short answer is yes, because in dim light you may inconsciously hold the book closer to your eyes or lean too close to the computer monitor. – b_jonas 14:39, 8 January 2006 (UTC)

global warming

if the effects of global warming starts to increase which city/region would be most affected?.....thank you! — Preceding unsigned comment added by 59.92.36.232 (talk • contribs)

It greatly depends on exactly what the patterns are and is very uncertain, and it depends on whether the warming is greater in some areas or others. Presumably, Holland might start to suffer the effects first, or any low-lying areas. (Israel, perhaps). Climate modelling is an interesting field. You might want to check out effects of global warming.

Which region is way too specific (let alone which city). Firstly, it is quite certain now that pumping all sorts of gases (most notably CO2) in the atmosphere will be a climatic effect, so there will be a climate change. This will most likely be global warming, which means just that. There will be a warming that is global, meaning worldwide. At least, that is what is most likely to happen in the near future. But the climate is so complex that it's hard to say what will happen next. One possibility is that the Atlantic gulf stream, which warms North America and Europe will stop, which might trigger an ice age. Of course, if heat no longer gets transported to the North it will remain at the equator, meaning that cold regions get colder and hot regions get hotter. But, like I said, what exactly will happen is very uncertain. It's a global experiment.

But one thing that is very likely to happen is the rising of sea levels, which will indeed threaten Holland and other lowlying parts of the Netherlands. But also other lowlying countries, some of which are among the poorest on Earth, such as Bangladesh and the Maldives, which don't have the means to protect themselves (we Dutch do, though even for us the expense might be crippling). Especially the latter get a lot of attention because the islands are so idyllic. Now isn't that a shame? Sure, but the population of 350 thousand is almost negligible compared to the 150 million of Bangladesh. Other densely populated lowlying areas can be found in the southern US, such as Florida. And New Orleans will get hit again unless a decent defence is put up this time. This won't hit as fast as a hurricane, though (a few decades maybe). But speaking of hurricanes. These get fed by hot sea water and global warming will of course also heat up the oceans. So there will be many more hurricanes. And one famous hurricane zone is the Caribbean. So again, the southern US. If you have any property there you'd better sell it now before other people start to wisen up too. DirkvdM 14:23, 7 January 2006 (UTC)

I vote for Tokelau: http://www.cia.gov/cia/publications/factbook/geos/tl.html

Since it is only 3 meters above sea level, I'm amazed it doesn't get wiped out by big waves now. Global warming and rising sea levels are sure to do it in, though. Also note that some areas will benefit. Greenland, for example, is covered by glaciation now. If those glaciers melt, it will be an enormous chunk of land available for development. Canada and Russia might also benefit, as most of their land masses are unusable arctic tundra at present. StuRat 17:54, 7 January 2006 (UTC)

computer rays

how do the rays from computers affect our eyes?

Look up, way up! (for Friendly Giant fans). It's the same as the general eyesight question. This must be a big thing on the homework front these days. --Zeizmic 15:02, 7 January 2006 (UTC)

well not exactly...i was just curious:)

What rays did you have in mind? Light rays enable us to see them, but see radiation for a description of other sorts of rays. I think the item that will best answer you question is Cathode_ray_tube#Health_danger. --Shantavira 16:28, 7 January 2006 (UTC)

ancient indian text on aviation

ancient indian hermit & philosophist bharadwaja concieved ideas about flyinh machines which could carry people.this was about 5000 yrs ago (supposition).many of his own designs as in the text,was later found to be in resonanace with,latest aviation theories.as science advances ,how his ideas can be dealt with,on grounds of modern engineering principles?

Many ancients thought of flying. Leonardo da Vinci was known for his engineering drawings of flying machines, among other things. The ancient Greek myth of Daedalus and Icarus also featured a flying machine. The idea that if birds can fly, then people should be able to fly if they just strap on a pair of wings is just wrong, though. People would need a completely different body design, with half our muscles in our arms, minimal legs, and lightweight, hole-filled bones, for that to work. The first concept needed for flying is the airfoil, which provides lift by moving forward without flapping the wings. The next concept is that control surfaces, or some other means of control (like a deformable wing) are needed. These things could have been discovered by the ancients, and could get you a decent glider using, say, a balsa wood frame with silk fabric. However, the development of internal combustion engines was necessary to make machines capable of true flight. StuRat 17:30, 7 January 2006 (UTC)

misleading websites

I keep coming across websites that are not what their name suggests they are, e.g. they might link to a competitor's website (like www.national-express.co.uk links to a rail site instead of a coach site), or all the useful-looking links from a fansite turn out to link to commercial sites or attempt to upload files to my computer. Is there a name for such sites? I am trying to remove them from Misplaced Pages but would like to know how to describe them. They don't necessarily seem to be mousetraps. --Shantavira 16:21, 7 January 2006 (UTC)

Yes, and I've also noticed misspellings of common websites, like http://www.gookle.com/, are packed with ads. The level of deception online is quite amazing, mainly due to a lack of laws and law enforcement actions. StuRat 17:15, 7 January 2006 (UTC)

A you suggesting there needs to be more control of the Internet? By who? The problem is not a lack of laws, it is people who are willfully ignorant. If people don't make the effort to educate themselves about how it works and don't learn to do a little bit of critical thinking they are going to be flimflammed regardless of how many laws get passed. I'm not talking about fraud--that is and should be illegal--I'm advising a bit of caution and caveat emptor.--◀Puck▶ 07:13, 8 January 2006 (UTC)

The terms you are looking for are Typosquatting and Cybersquatting. David D. (Talk) 18:18, 7 January 2006 (UTC)

Adams apple

What signifince do larger Adam's apples have? What causes protuding adams apples, and what does this mean in terms of the body?

A protruding Adam's Apple could be a sign of an enlarged thyroid gland. My brother had that and had thyroid cancer. So, go to a doctor and have it checked out. StuRat 20:38, 7 January 2006 (UTC)

The Adam's Apple is the protrusion of the thyroid cartilages of the larynx. The larynx is essentially a semi-rigid box that facilitates resonance from the vocal cords. The significance is that its owner may posess a deep voice. There are several factors contributing to the normal variation of degree of protrusion, including, but not limited to:

1. Gender (male>female)
2. Developmental stage (prepubescent<adult)
3. Body fat (fat neck hides it)
4. Individual anatomic variation

There are also pathologic reasons for enlargement of the Adam's Apple, however, these usually result in an observable increase in size of the structure over time, that cannot be readily explained by normal causes, such as onset of puberty. Thyroid cancer can cause swellings in the neck, and these usually occur first at the front of the base of the neck, below the Adam's Apple. Thyroid cancers are also (usually) not as firm to the touch as the Adam's Apple is, and are often asymetric in appearance. Any concern about cancer is best addressed by your doctor - if you have any new swelling or mass or spot or whatever, anywhere, get it checked out. Far better to be told its normal than sit on something deadly. --Mattopaedia 01:25, 8 January 2006 (UTC)

scientific method

i am a student doing some studying for midterms, and i am desperate to find the answer to this question: Knowledge and application of the scientific method:

• question
• hypothesis
• design/perform experiment
• collection/ analysis of data
• conclusion
• communication

i'm only in the 6th grade and i need some help. if you end up spelling something wrong i probably will correct you because i am the number one speller in my county. thank you! sorry if i sounded like i was showing off.

from,

1. 1speller

• You don't actually have a question there. The sure tip-off is the lack of a question mark. Also, you might want to extend your spelling skills to the proper capitalization of words.StuRat 18:42, 7 January 2006 (UTC)

well typically i'd need to know the application of the scientific method to those, hey i'm only 11.

• I don't think 11 is too young to capitalize. In some cases, I don't even think it's too young for capital punishment. StuRat 02:25, 8 January 2006 (UTC)

• Hi there chum! I've formatted your post a little better so hopefully it will be more readable. What you have described is generally what is taught as "the scientific method". We have an article on the scientific method which might be somewhat useful, but it is probably more complicated than what you can use. The basic point of the scientific method is to ask questions about nature which can be checked to be right or wrong. What your midterms are probably requiring you to know is how each of those steps participate in doing this. Try looking at our article and see if it makes sense to you, if not maybe others can help out. --Fastfission 19:32, 7 January 2006 (UTC)

Wow, whoever wrote scientific method really has a thing for elevated vocabulary. Black Carrot 23:38, 7 January 2006 (UTC)

I hate when people write in unnecessarily complex terms. Please feel free to simplify it, to make it readable by a general audience. StuRat 01:05, 8 January 2006 (UTC)

I agree. I mentioned it on the talk page so maybe they'll attempt to rewrite it. To #1speller you really need to work on punctuation. No capitals at all looks quite lazy. I assume you don't wish to give this impression? David D. (Talk) 01:10, 8 January 2006 (UTC)

• Good luck: There is a small entry on the scientific method in our simple English Misplaced Pages, which is designed to be more easy to understand than our other entry. Perhaps it will be useful. --Fastfission 00:36, 8 January 2006 (UTC)

Your what? Black Carrot 02:05, 8 January 2006 (UTC)

Argg, I tried to link to the simple Misplaced Pages but I did it incorrectly, obviously. Anyway I fixed it now. --Fastfission 17:18, 8 January 2006 (UTC)

Holy cow! That article is unreadable. It's way beyond my assumed audience of 'National Geographic' (or grades 10-12). How could one tackle this? --Zeizmic 15:15, 8 January 2006 (UTC)

ps. I take this all back. I read the discussion, and I wouldn't touch it with a 10' monotone soliloquy. --Zeizmic 15:30, 8 January 2006 (UTC)

Is it possible to provide a link from the main Scientific Method page to the simple one? Black Carrot 19:57, 8 January 2006 (UTC)

verizon

What do you want to know about it ? StuRat 03:35, 8 January 2006 (UTC)

Router for large network

Is there a limit to how many computers a router can handle? Should a standard 4-port router such as the Linksys BEFSR41 be enough to serve IP addresses to a network of 30 or more computers via various switches, hubs and wireless access points? If not, what kind of a router is needed? Thank you, Adam Konner 19:06, 7 January 2006 (UTC)

Routers don't specifically "serve IP addresses" (unless the router is also doing something else, or unless this is what you are meaning by NAT). What is the router actually doing in your network? Notinasnaid 19:08, 7 January 2006 (UTC)

Jebums, that was fast. My router serves as a gateway between the LAN and the cable modem, and also as the network's DHCP server, hence the serving of IP addresses. --Adam Konner 19:17, 7 January 2006 (UTC)

Well, there are two things to worry about: limitations – for example I have seen a firewall that will only allow 50 IP addresses; and performance. From a performance point of view, cable internet connections are incredibly slow, compared to the potential network speed, so even the cheapest router isn't likely to be fazed. Routers are able to be used to connect two full speed wired networks. Limits you'd need to check the documentation for your specific router. It also needs a sufficient supply of addresses for DHCP of course, but that's under your control. DHCP itself puts a trivial load on its server. Notinasnaid 19:31, 7 January 2006 (UTC)

Here's why I wonder: When I asked the Comcast guy if the new service would be sufficient to support 30 computers, he said that would be fine, all I'd need is a router that can handle all those computers. I can't find anything in the router's documentation about it. Searching for answers on the internet, I found this webpage that says, "On an eight-port wireless router, you may only use a total of eight connections, not eight wireless and eight wired." However, now I've found another page that seems to contradict the first one. By the way, when you say cable internet is incredibly slow, do you mean relative to ethernet networks (obvious) or relative to DSL? --Adam Konner 19:57, 7 January 2006 (UTC)

Just relative to a 100 mbps wired ethernet. Is this router also a wireless access point? Notinasnaid 20:29, 7 January 2006 (UTC)

No, we have a high-powered antenna (AirPoint PRO Outdoor) attached via ethernet. Why? --Adam Konner 20:40, 7 January 2006 (UTC)

I think we are talking pure dedicated routers here without wireless or multiple ports. I have an old Netgear RT311 and it chokes with the multiple IP connections that gtk-gnutella generates. I have to knock that value way down. I can't find specs on general router processor speed, and #IP connections, but I am sure this is important for 30 computer connections. --Zeizmic 23:04, 7 January 2006 (UTC)

Do hippos have enemies?

Someone inserted the following passage:

• The only animal of any danger to the hippo is the rhino, which is a lethal enemy to our friend the hippopotamus.

Don't worry, it got of course deleted. But the question remains: Do hippos have enemies? Common Man 19:11, 7 January 2006 (UTC)

• I can think of one... (I don't think full-grown hippos have a natural enemies, but I don't know for sure) --Fastfission 19:21, 7 January 2006 (UTC)

Yes, sadly there are two types of human enemies: poachers and warriors according to Hippopotamus#Extinction. Common Man 19:31, 7 January 2006 (UTC)

yeah, human beings, in short. Even those who don't directly kill them but indirectly destroy their habitat by wasteful consumption. deeptrivia (talk) 21:08, 7 January 2006 (UTC)

Anything other than people? Black Carrot 02:07, 8 January 2006 (UTC)

Crocodiles. There was a documentary on television last month about hippos. It showed a young hippo swimming around and then killed and eaten by a croc. As for the human/hippo relation, the hippo kills more humans in Africa each year than any animal other than other humans. --Kainaw 02:25, 8 January 2006 (UTC)

I'm sure from the hippos' point of view we've got it coming to us.--◀Puck▶ 06:41, 8 January 2006 (UTC)

PS3 GPU RSX

There is a rumor going on on the internet that say that the PS3's GPU codenamed RSX developed by Sony and Nvidia is less powerful then Nvidia's upcoming GEFORCE 7800 GTX? Is this true? If it is true then that would mean that the PS3's graphics are going to be obselete compared to computers that would use the 7800GTX.

The "RSX" that the PS3 uses is basically a copy of the 7800GTX except the "RSX" may be a little faster. As with all consoles and the PS3 is no exception, every console is obsolete as soon as they are released because high end gaming computers catch up and eventually surpass console hardware technology in a couple of months.

Having said that, console graphics have an advantage in that programmers learn to get the most out of the hardware over time, so console graphics (I think) do improve slightly despite the actual hardware being the same. --Sum0 20:27, 7 January 2006 (UTC)

To say the same thing with different words, PC game developers must cater for the widest range of videocards, cpu and ram configurations, so any features that are are harder to implement and less likely to work on common hardware won't make it into the product. But I think it's plain to see the relationship between graphics and gameplay is now not 1:1 at all, it is necessary to pump exponentionally(?) more effort into graphics capability to increase the enjoyability levels linearly. Tzarius 03:20, 8 January 2006 (UTC)

What causes the magnetic dipole moment of an atom?

I've read our articles on magnet and magnetism, which say that magnetic fields are caused by the motion of charges, but then add that electrons in atoms don't actually move. What electrons actually do in atoms, apparently, is (i) to sit around in orbitals and (ii) to possess a property called spin, but they neither orbit nor spin in the mechanical sense. How does this mysterious behaviour create a magnetic dipole? I'd like to add the answer to this question to our articles, even if it's just that "nobody knows". --Heron 20:49, 7 January 2006 (UTC)

Well, quantum spin isn't exactly like mechanical rotation, but they do share many properties. I think every particle with both charge and spin has a magnetic moment, including the proton and the electron. Even the neutron has a magnetic moment, because it is made of spinning, charged quarks. —Keenan Pepper 22:46, 7 January 2006 (UTC)

There is two direct contributions to an atomic magnetic moment: Electron spin and spin-orbit coupling. Electron spin is the biggest contribution, and basically comes from the fact that each electron has a magnetic moment, and therefore the magnetic moment of an atom is equal to the difference between the number of spin up and spin down electrons. If you like, each electron is a tiny dipole, and an atom gets the net sum of those.

Spin orbit coupling is more involved, and arises from relativity - Diracs equations describe this. It's not possible to give a non-relativistic analogy directly. The 'spin-only' approximation is close enough for many purposes, however. Syntax 23:07, 7 January 2006 (UTC)

Thanks. I'll revisit the magnetism-related articles. There were some contradictory statements, about electrons moving/not moving, that I was unhappy with. By the way, can you give me an idea of the accuracy of the 'spin-only' approximation? A few per cent, or a few parts per million? --Heron 12:36, 8 January 2006 (UTC)

It's around 10% out. That is, however, enough to clearly identify the net spin of a atom. See for some example numbers. Note that, as that page is aimed for chemists, it's talking in terms of moles of ions, not individual atoms. Also, on the electrons moving / not moving thing - note that there are multiple equivilent ways of describing the same phenomena. You can describe electrons as moving but not emmiting EM radiation, or as static but generating a magnetic moment, and you ends up with the same sort of descriptions; both of these are approximations to the real situation. Syntax 14:47, 8 January 2006 (UTC)

I was thinking about differences in electronegativity between atoms, but then I realise that is the cause of dipole momenets in molecules, not atoms. But I'd thought I mention it anyway. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 15:43, 8 January 2006 (UTC)

January 8

Circulatory System

== How long does it take for a drop of blood to travel through your entire body? ==

Could a link please by supplied to a reliable source... thanks --Ike 01:18, 8 January 2006 (UTC)

Well, you're going to have a hard time finding a straight answer, because blood doesn't travel in drops, and some paths back to the heart are short while others are very long (going through mazes of capillaries). —Keenan Pepper 02:41, 8 January 2006 (UTC)

Keenan's right. Any given drop of blood will travel along random pathways throughout the circulatory system, and during that journey the fluid and cellular components of blood are continually exchanged. So the answer to your question is : "it depends".

Of more use to you may be that there is a way of averaging this, which doctors use, based on a person's cardiac output. The link, & its links, give some reasonably detailed information, but in short:

• Average heart rate =70 beats/minute, average stroke volume (amount pumped in a single beat from the left ventricle) = 70mL.
• Cardiac output = Heart rate x stroke volume, so cardiac output = ~4.9L/min. (A gallon is about 4.5L if you're in the US & don't do metric). -- Clearly I don't do antiquated and unnecessarily complex measurement systems. A gallon is 3.785L according to this. --Mattopaedia 08:37, 8 January 2006 (UTC)
• Average blood volume is about 8% bodyweight in kg. So for the "average" 70kg man, blood volume is about 5.6L.
• So, the heart pumps the equivalent of total blood volume about every 68 seconds.

Any human physiology text can give you these details. To check my numbers, I used Guyton & Hall (1996), Textbook of Physiology (9th Ed). Hope that helps. Mattopaedia 05:47, 8 January 2006 (UTC)

how does an oil derrick function

Have you looked at Oil derrick? Black Carrot 06:38, 8 January 2006 (UTC)

When was the first offshore oil drilling rig in the US built?

It seems in 1894, "Summerland, the first offshore oil field to be developed in the United States, had been discovered near Santa Barbara, California." In 1903, a "wooden pier that rested on stilt-like piles stretched out into the ocean at Summerland and a number of rigs drilled from it." - Akamad 03:49, 8 January 2006 (UTC)

Black Holes

I am a tad confused about the concept of, what is described in our article on black holes as "narrow jets of particles at relativistic speeds." I was wondering how this works, because I was under the impression that the gravity in a black hole was strong enough such that no matter can escape its gravitational pull. So how is it possible that the black hole can "eject" particles outwards and away from it's über strong gravity? Thank you. - Akamad 03:42, 8 January 2006 (UTC)

The particles are not coming from inside the black hole, but from the accretion disk of matter around it. The particles can still escape from the black hole's gravity as long as they have not passed the event horizon. —Keenan Pepper 06:03, 8 January 2006 (UTC)

In fact, this allow virtual particles that form at the edge of the event horizon but not past it, to separate from each other before they annihilate, then being ejected, resulting in hawking radiation. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 09:50, 8 January 2006 (UTC)

Thanks for the responses. - Akamad 19:20, 8 January 2006 (UTC)

Jews

Are Jews (the people group, not the religion) smarter as a race? Because there seems to be alot of famous Jewish people, for exanple 22% percebt of Nobel Prize winners are Jews. So, do the Jews have a genetic or ethnic advantage in mental intellengence?

I don't think so, but i do think that Jewish people are extreeeemely cool :D --Cosmic girl 04:00, 8 January 2006 (UTC)

Misplaced Pages has an article on Race and intelligence. - Akamad 04:34, 8 January 2006 (UTC)

The typical explanation is that Jewish culture values education and study more than other cultures. StuRat 07:25, 8 January 2006 (UTC)

Speed of light

If nothing can reach the speed of light, why can light or electrons reach it?

Nothing can exceed the speed of light, and from what I gather, electrons cannot reach the speed of light anyway. - Akamad 04:25, 8 January 2006 (UTC)

And light, by definition, travels at the speed of light in a vacuum. - Akamad 04:30, 8 January 2006 (UTC)

If the light is not in a vacuum, it gets slowed down and other things (such as electrons) can travel faster than it. --AySz88^-^ 04:37, 8 January 2006 (UTC)

(edit conflict) It is not exactly true that nothing can reach the speed of light. To be more precise, although still not very precise, it is, according to current physics, impossible to accelerate matter up to or beyond the speed of light; that is, the speed of electromagnetic radiation in a vacuum. It is theoretically possible to have particles that have an imaginary rest mass and so always travel faster than light (tachyons), and I believe that photons (the particle associated with light), being massless, must travel at the "speed of light". Also note that the relevant limit is c, the speed of light in a vacuum. Electrons can be accelerated to very close to c. If they are traveling in something like glass or water, they can actually travel faster than light can travel in that medium, without ever exceeding c. This produces Cerenkov radiation, approximately similar to a sonic boom. This explanation is oversimplified and others more knowledgeable than I should feel free to correct me. — Knowledge Seeker দ 04:45, 8 January 2006 (UTC)

It's a common misconception that electrons go the speed of light in a wire. The electric current as a whole does go the speed of light, but the individual electrons don't go anywhere near that speed. The average speed of the electrons (the drift velocity) is about a millimeter per second, depending on the thickness of the wire and other factors. A good analogy is a water faucet. When you turn the faucet on, water instantly comes out, but that doesn't mean it came all the way from the water tower in that amount of time. The water was waiting in the pipe. When you turn on a light switch, the electrons going through the light bulb were already there waiting in the wires. They just get "pushed out" by the electrons coming from the power plant, so to speak. —Keenan Pepper 06:14, 8 January 2006 (UTC)

And to further clarify to other readers, the speed of light of an electric current comes in if say, that power plant was two light seconds away (and ignoring what would be massive amount of electric resistance in the wire, let's just assume it's a mile thick :p), then it would take two seconds for the electrons in the filament of the light bulb to start moving the moment the switch is flicked. The electrons from the power station electrons 600,000 km away (roughly) will take two seconds to push all the electrons between them and the electrons in the filament in order to get the electrons in the filament going. This is a necessary consequence, because otherwise you could transmit physical information (which represents order, something covered by the laws of thermodynamics faster than c. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 09:58, 8 January 2006 (UTC)

is breaking the sound barrier as easy as snapping your fingers?

is breaking the sound barrier as easy as snapping your fingers? if you snap your fingers, is the resulting sound due to breaking the sound barrier, the subsequent impact, or simply the loss of force due to friction?

The sound comes from your fingertip hitting the base of your thumb. No sonic booms involved. —Ilmari Karonen (talk) 05:58, 8 January 2006 (UTC)

I agree there's no sonic boom, however I think your statement isn't completely true. When you click your fingers, what causes the sound is that you lean your ring finger to the base of your thumb and you snap your middle finger to it. If you do not put your ring finger there, and snap your middle finger that way, you don't get a click, only a much weaker thump sound, because the pad at base of the thumb is much softer than your ring finger which has a bone close to the surface. (It it, however, possible to use different fingers instead of the middle and ring finger and still produce the clicking sound, but this combination is the best. You can even use a finger of your other hand instead of your ring finger.) I am not sure, but I think that the vedge-shaped gap formed between the ring finger and base of the thumb might also take part in producing the sound.

For a sonic boom, you need an object moving with at least 300 m/s, and I don't suppose your finger would move with more than 0.5 m/s in a simple finger clicking. – b_jonas 14:09, 8 January 2006 (UTC)

Snapping a whip is the easiest way to create a sonic boom. StuRat 07:09, 8 January 2006 (UTC)

Light in orbit

Given that light can be pulled inwards by gravity(by something as massive as a black hole), and that it has a reliable velocity, and that those are the only two characteristics necessary for something to move into orbit around a celestial body, it there light endlessly orbiting black holes? Is there a distance out from a black hole at which, if you weren't pulled apart by the gravity or something like that, you would see a ring of light all around you? Because that would be pretty cool. It'd be fun to imagine something so absolutely black(except radiation) being encased by a sphere of pure light. If so, would that be near the event horizon? One problem I've found with this is that black holes are constantly expanding, so the orbital distance would be increasing as well, meaning any light currently in perfect orbit would eventually get pulled in, but maybe that's not a problem. --Black Carrot 06:52, 8 January 2006 (UTC)

I believe the orbital distance would be the event horizon. You are right that those orbits would be unstable due to the increasing size of the black hole. Therefore, I would expect you would find some, but not much, light in orbit at any given time. StuRat 07:13, 8 January 2006 (UTC)

Yes, as I understand it, the event horizon would be defined by the distance at which light almost escapes but not quite, and would therefore presumably contain some light "orbiting" the black hole. However, it would not appear as a sphere of light as you describe. If you are at a distance from the black hole, the light is on the event horizon and therefore unable to reach your eyes. Remember, for you to see a photon, it must reach your eyes. It doesn't shine in all directions. If it's orbiting, it will be invisible unless it breaks free somehow and travels toward you instead. Note that you may be able to see black-hole–related phenomena, including light trapped near the event horizon, but orbiting light shouldn't be one of them, as far as I can tell. — Knowledge Seeker দ 07:36, 8 January 2006 (UTC)

If a black hole had a constant mass and a photon would be in orbit at that distance (I'll assume that that's the event horizon) then it would stay there, I presume. But how would it get there? As soon as it's within the event horizon it's lost. So it has to approach from the outside. The only way for it to do that would be to spiral in. But because it has to stabilise at exactly that distance that would only happen after an infinite amount of time. So I imagine there might be a halo of spiralling (not orbiting) photons just outside the event horizon, but none exactly at the event horizon. But even if the black hole were to expand a bit, then I don't think any photons would fall into place in that orbit, but that's just gut feeling. DirkvdM 10:09, 8 January 2006 (UTC)

The photons could also come in along a tangent to the event horizon, or what works out as a tangent, taking into account the bending of the ray, as it approaches the black hole. Also note that objects falling into the black hole would tend to dislodge photons from orbit as they pass the event horizon. StuRat 11:08, 8 January 2006 (UTC)

I am not an expert from this, but I'll try to give some answers. You can find some interesting discussion on these effects on .

From what I understand, there is indeed such a sphere where light could circle endlessly, and this can happen not only for black holes but other very dense stars that are not dense enough to form a blackhole but aren't far from it. However, this light orbit is not stable: light circling on that sphere will eventually either fall in or escape outwards, so there will be no glowing "sphere of pure light". However, this sphere can cause odd visual effects, namely you can see distorted images of the sky around that are from photons that have circled near this sphere a few times.

Also I think this sphere is not the event horizon, but it is outside of it, but I am not sure of this (I think I don't even understand what the event horizon is exactly). – b_jonas 13:16, 8 January 2006 (UTC)

You're correct. At the distance where light moving in a circle around the hole stays in orbit, light moving away from the black hole can still escape. If you could stand there, the black hole would appear to cover exactly half of the sky. At the event horizon, on the other hand, no light can escape. A hypothetical observer standing motionless at the event horizon would see the black hole cover the entire sky, with the possible exception of a single point of light straight above. —Ilmari Karonen (talk) 16:06, 8 January 2006 (UTC)

(Well, that is, if a) it was possible to stay motionless at the event horizon, and b) we could ignore all this weird stuff about space and time being relative. But you get the idea.) —Ilmari Karonen (talk) 16:11, 8 January 2006 (UTC)

What I don't understand is that the page I linked above claims that this sphere has a radius that's a constant multiply of the radius of the event horizon. But it also claims that dense neutron stars that aren't black holes could also have such a sphere. Don't these two claims contradict? – b_jonas 21:18, 8 January 2006 (UTC)

Security vulnerability

In a typical software company (like Microsoft, Apple, Sun Microsystems, etc.), did the programmer(s) responsible for a security vulnerability (wrote the code that caused the vulnerability, that is) got punished or disciplined in some way? --61.94.149.59 07:28, 8 January 2006 (UTC)

There is an assumption in your question that all vulnerabilities are due to either malicious or unintentional errors by programmers. On the contrary, I think many vulnerabilities are inherent in the high-level design of a program. If programmers are asked to make an operating system that will execute programs on your computer which are downloaded off the internet, without your permission, this is an inherent vulnerability. Think of it as if you left your house key under the door mat in case somebody needed access to your house, like a firefighter. Obviously, anyone can find the key and gain access. You can add a supplemental security system that denies access to people it regonizes as bad, but that still lets lots of bad people in which aren't recognized. Similarly, a virus-check program can only stop those viruses it recognizes. A more practical approach to security would be to ban all access to your computer to everyone you haven't specifically authorized to have access. StuRat 08:23, 8 January 2006 (UTC)

Uh, I think I should be more specific. Actually, what I mean is security vulnerability caused by programming mistakes (e.g., incorrect authentication routines, unchecked buffer, etc.), not security risks in general. To be more specific, do someone in the company get punished for making mistakes in program code that turned into a security vulnerability? 61.94.149.59 08:55, 8 January 2006 (UTC)

As a general rule, there are computer companies that flood us with vulnerabilities that should never have been there in the first place, and there are computer companies you never hear in the news about vulnerabilities because we go 10 years or more between them having a flaw (IBM for example). This is because the latter have systems to catch vulnerabilities in development before the product goes to the customers, This requires extensive testing of the software, which adds to the cost of the product. Because the market demands cheapest possible products, the market gets what it pays for, products that have not been properly tested to make sure they have no security vulnerabilities. If the programmers that did the poor programming are no longer working at the place where they did the bad code, it is unlikely that the company will go after them, if it even knows who done it. The industry, that has won the market share war, has a dismal record of security standards, compared to in computer historical standards where quality was mission critical. User:AlMac| 09:10, 8 January 2006 (UTC)

Also, note that when you open any software package you agree that the company will not be held responsible for any damage caused to you or your business even as a direct result of defects in their product. If car makers could be assured that they would not be sued, the car defect rate would be as high as the software defect rate. The lack of responsibility leads to, well, irresponsibility. StuRat 09:39, 8 January 2006 (UTC)

In any company, employees can make mistakes, sometimes very expensive or embarrassing ones. How companies deal with this is rightly a secret: between themselves and the employee, and generally dealt with case by case. Some companies punish those who make mistakes, but others have learned that this only encourages ingenuity in hiding them until they become more serious. In some companies, corporate embarrassment is severely punished, by sacking a senior person in charge. Software companies generally learn that if you sack every programmer who makes a mistake, then you won't have any programmers. Notinasnaid 11:14, 8 January 2006 (UTC)

As a computer programmer myself, I can tell you most of us would very much want to thouroughly test and fix our software, but management budgets and schedules don't allow this. So, blaming the programmers is a bit like blaming a homebuilder who you told to build you a mansion in a week for a thousand dollars. StuRat 11:50, 8 January 2006 (UTC)

How do solar sails work ?

I understand that light hits the sail and is reflected back off the sail. My question is how masslesss photons can exert any pressure on the sail. When I use F = ma to calculate the force, even if the acceleration is from the speed of light in one direction to the speed of light in the reverse direction, I still get a force of zero for a massless particle. What am I missing ?

There is a device with a similar function, a "fan" inside an evacuated glass container with one side of each blade painted black and the other white. The difference in reflectivity causes the fan to rotate when in the light. This might be a purer example of the effect I'm asking about, since solar sails will also catch particles in the solar wind which do have mass. StuRat 08:03, 8 January 2006 (UTC)

The "fan" (Crookes radiometer) seems to work on something completely different from the solar sail. The light mill needs gas particles to work (i.e. a partial vacuum, not a total vacuum). --AySz88^-^ 08:27, 8 January 2006 (UTC)

According to solar sail, the pressure comes from radiation pressure. Have a look at that article; it explains how it works. enochlau (talk) 08:39, 8 January 2006 (UTC)

I've read that article, and it really didn't explain it, just gave a formula to find the strength:

It may be shown by electromagnetic theory, by quantum theory, or by thermodynamics, making no assumptions as to the nature of the radiation, that the pressure against a surface exposed in a space traversed by radiation uniformly in all directions is equal to 1/3 the total radiant energy per unit volume within that space.

For black body radiation, in equilibrium with the exposed surface, the energy density is, in accordance with the Stefan-Boltzmann law, equal to σT/3c; in which σ is the Stefan-Boltzmann constant, c is the speed of light, and T is the absolute temperature of the space. One third of this energy is equal to 6.305×10T J/mK, which is therefore equal to the pressure in pascals.

I'm really looking for an intuitive explanation. I suppose if it involves quantum mechanics or something else inherently non-intuitive, I will just have to accept it without understanding it. StuRat 09:09, 8 January 2006 (UTC)

Photoelectric effect. It's not really the same context as a solar sail, but it ends up ejecting electrons (which bear mass) - so it is ultimately the same principle. F=ma is an incomplete formula: it is incompatible with quantum mechanics. I myself am searching for a better formula (I have a hunch that one exists) that will account for the force a photon exerts on a mass, but also compatible with classical mechanical situations. (ie. breaking down the "mass" into different components). Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 10:02, 8 January 2006 (UTC)

Energy is mass in a different form. So if mass can propell something, energy should also be able to do that. But mass can only propell something when it has energy (which it then transfers to the object being moved). So energy is the only thing that is needed, I'd say. Which makes sense of course. What happens to a photon that hits a sail (or anything else for that matter)? Does it lose its energy=mass and thus get transformed into something else? I understand from photoelectric effect that photons (being electromagnetic radiation) knock electrons out of the material they hit. But then the sail would be 'eaten away'. DirkvdM 10:17, 8 January 2006 (UTC)

Having electron constantly leaving the material does seem like a problem, unless they are somehow created by the photons which hit. I didn't think the photon lost any energy, but just changed it's direction, like a perfectly elastic ball bouncing off a wall. Also, I don't see energy as equal to mass but rather as something that can theoretically be converted into mass. As far as I know, this doesn't happen in a solar sail, however. StuRat 10:22, 8 January 2006 (UTC)

I thought about it a bit more, and I suppose losing electrons at a sizable portion of the speed of light would accelerate the object to a similar portion of the speed of light (although this might take thousands of years). A large positive charge would seem to build up on the solar sail, however, as it becomes deficient in electrons. I would think this charge would build to a point where it would suck any ejected electrons right back down. StuRat 10:43, 8 January 2006 (UTC)

It'll probably generate current and the electrons simply go to another part of the sail (which then the current replaces the electrons the metal atoms lost). The energy would then probably eventually contribute to the driving force on the sail anyway. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 15:40, 8 January 2006 (UTC)

I don't see how this solves the problem of the sail taking on a net positive charge and thus a huge attraction for any electrons which manage to get free. StuRat 20:51, 8 January 2006 (UTC)

The problem is that I think the relationship between mass and energy in correspondence to force isn't e=mc^2, but something entirely different, based on the entire premise that say, a body that isn't moving doesn't bear any force anyhow, but of course, holds energy. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 10:23, 8 January 2006 (UTC)

It is true that photons have zero mass (zero rest mass, to be precise), but they do have momentum. This allows you to use conservation of momentum to calculate the radiation pressure. You may think that momentum implies mass, but physicists say that this is not true (see "Does light have mass?" on Physics FAQ). --Heron 12:03, 8 January 2006 (UTC)

I'm just a lowly engineering science-type guy, but this just F=Ma with the solar particles, and perhaps radiation (the wave-particle thingie). Solar sails are a thing of the past, I think good old ion engines with nuclear power are way better! --Zeizmic 17:10, 8 January 2006 (UTC)

Obsolete before they have even been made to work yet ? StuRat 20:51, 8 January 2006 (UTC)

hEARing

I believe we have body activity patterns we have subconsiously learned to ignore.

What causes me to intermittently hear my heart beating out of my right ear? (I am assuming that is what I am hearing.) Is that a symptom of some ear problem?

I went for months without this distraction, then had it on and off a couple days, typically hald a dozen short sessions of perhaps 1/4 hour worth, then a rest for a while, then another session, and now I have peace and quiet again. I not remember my left ear hearing this in ages.

I will be age 62 this Feb 8 and fear that as our bodies grow older, they develop new aliments. I sure hope this nuisance is not going to be another of those new ailments, I will have to learn to live with. User:AlMac| 09:17, 8 January 2006 (UTC)

Just about everyone could hear their own heartbeat in complete silence. Hearing your heartbeat at normal background sound levels may be a sign of high blood pressure, however. I suggest you get a BP cuff and take your BP the next time this happens. Also take some "baseline" readings when you don't hear this sound, to see what your normal reading is. Spikes in BP may be caused by certain conditions, such as sodium sensitive hypertension. It would be a good idea to consult a physician, as untreated high BP can be quite dangerous. StuRat 09:32, 8 January 2006 (UTC)

I'm no expert at this at all, but isn't high blood pressure a symptom rather than an ailment? For example for blood clots? To continue with this thought, I can imagine that if a tiny clot would end up in a small blood vessel near the inner ear that could have such an effect. A remedy might then be taking aspirin (an anticoagulant). Or alcohol, for a happier alternative :) . DirkvdM 10:29, 8 January 2006 (UTC)

No, I think hypertension, AKA, high blood pressure, may be considered an ailment by itself. It could also be viewed as a result of bad diet, obesity, age, etc., and a cause of things like stroke. StuRat 10:47, 8 January 2006 (UTC)

spiders : how do they build some nets?

I need to make a question to a spiders expert because I need information on how some spiders build their nets, everybody speaks about nets and spiders but nobody actually explain how some extraordinary patterns are made! I saw 9 metres nets long in orizontal direction with nothing in between!!! How can they build it???We use elicopters but they do not! waiting for answer Raffaele Serafini Veneto-Europe

raffaeleserafini@tiscali.it

I think you mean webs. There are also some spiders which make portable nets, but I don't think that's what you're asking. Each species has a different technique, but here's a general overview of web design:

1) First they drop from the highest point and leave a non-sticky line behind. They then anchor this at the lowest point, too.

2) They then climb back up the line and repeat another line but anchor it at the center of the orignal line as well as at the top and bottom. This new line might be rotated, say 30 degrees, about the center from the first line.

3) They repeat this until they have all the axial lines in non-sticky silk.

4) They then connect some cross supports with non-sticky thread, maybe 2 or 3 concentric sets.

5) Now it's time to add the sticky silk in a radial pattern between the supports.

6) Depending on the spider, they might go to the center or to the edge to wait for a victim. Once they feel vibrations on the non-sticky lines, the follow them out to the prey and kill it.

StuRat 11:41, 8 January 2006 (UTC)

Caves

Section title added
WHICH IS THE OLDEST CAVE IN THE WORLD`````````

Please don't use all CAPITAL LETTERS; it looks you are shouting. I don't think that there is any 'oldest' cave; many caves have existed since prehistoric times. smurrayinchester 14:11, 8 January 2006 (UTC)

Probably since the Earth was formed too. Elle vécut heureusement _{toujours dorénavant} (Be eudaimonic!) 14:49, 8 January 2006 (UTC)

It's possible he means the oldest cave that's used as a tourist attraction. Black Carrot 20:11, 8 January 2006 (UTC)

sound

if all objects create sounds by vibration then what is doing the vibrations?

Not a true assumption. Could you clarify? --Zeizmic 15:17, 8 January 2006 (UTC)

Please see sound. -- Rick Block (talk) 18:51, 8 January 2006 (UTC)

Any part of an object can vibrate. That vibration pushes on the air/water/etc, which makes that vibrate. The vibration of the air makes your ear drum vibrate, which is how you hear. Black Carrot 20:15, 8 January 2006 (UTC)

Some other form of energy creates the vibrations initially. For example, during an explosion chemical potential energy is changed into various other forms of energy, including sound vibrations. StuRat 20:41, 8 January 2006 (UTC)

HTML tag for verdana text?

I'd like to make the text on a HTML page appear in Verdana (obviously only when installed on the PC of the viewer). '' and '' don't work, and a Google search yields nothing. Can anyone help me?

 <span style="font-family:verdana">Your text</span>

 <span style="font-family:verdana,sans-serif">Your text</span>

  <style type="text/css"><!--
  h1 { font-family:verdana }
  p { font-family: verdana }
  //--></style>

  <h1>Page title</h1>
  <p>This is some text that will appear in Verdana.</p>
  <p>Here is some more text also in Verdana.</p>

<div style="font-family: Verdana, sans-serif"><table>
 ...
 </table></div>

 <style type="text/css">
 td { font-family:verdana }
 </style>