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| '''Tired light''' is the hypothesis that light slowly loses ] as it travels through space. Since a decrease in energy corresponds to an increase in wavelength, this effect would produce a ] in spectral lines that increases with the distance of the source. It was originally postulated in 1929 by ] as an alternative to the standard interpretation that the ] is caused by ]. Most physicists and astronomers do not believe that such an effect can account for cosmological redshifts. | '''Tired light''' is the hypothesis that light slowly loses ] as it travels through space. Since a decrease in energy corresponds to an increase in wavelength, this effect would produce a ] in spectral lines that increases with the distance of the source. It was originally postulated in 1929 by ] as an alternative to the standard interpretation that the ] is caused by ]. Most physicists and astronomers do not believe that such an effect can account for cosmological redshifts. | ||
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| The simplest form of a tired light theory assumes an exponential decrease in photon energy with distance traveled: | |||
| :<math>E(x) = E(0)e^{-x/R},</math> | |||
| where <math>E(x)</math> is the energy of the photon at distance ''x'' from the source of light, <math>E(0)</math> is energy of the photon at the source of light, and ''R'' is a large constant characterizing the "resistance of the space". To correspond to ], the constant ''R'' must be several giga]s. <!--How large exactly? Does the exponential form match the redshift observations in detail?--> Various mechanisms to produce such a drop in energy have been proposed. ] by known mechanisms from gas or dust does not reproduce the observations. For example, scattering by any mechanism would be expected to blur the images of distant objects, which is not observed. | |||
| In recent years, new tired light mechanisms have been put forward (Marmet 1988), in which photons lose energy by interacting with electrons and other particles in intergalactic space. According to standard theory, ] is radiated away at any collision with a charged particle such as an electron so that a very small energy loss occurs at each interaction, which arguably results in a redshift. | |||
| However, such tired light mechanisms alone cannot fully explain cosmological redshift: they can not replace the Doppler explanation. Tired light models have not reproduced the successes, beyond Hubble's law, of the standard ] cosmology. They do not account for the observed time dilation of distant ]e light curves (Wilson, 1939 and Goldhaber, 2001), the black body spectrum or anisotropy of the ], and the observed change in the morphology of high redshift ], ]s and ]s. | |||
| ==References and External Links== | |||
| *Zwicky, F. 1929. ''On the Red Shift of Spectral Lines through Interstellar Space.'' PNAS '''15''':773-779. | |||
| *Wilson, O. C. 1939. ''Possible applications of supernovae to the study of the nebular red shifts.'' Astrophysics Journal '''90''':634. | |||
| *Goldhaber, G., et al. 2001. (Supernova Cosmology Project). ''Timescale Stretch Parameterization of Type Ia Supernova B-band Light Curves.'' | |||
| *P.Marmet, ''A New Non-Doppler Redshift'', Physics Essays, Vol. 1, No: 1, p. 24-32 (1988). | |||
| *http://www.astro.ucla.edu/~wright/tiredlit.htm Edward Wright of ] provides a detailed criticism of tired light. | |||
| * W. Jim Jastrzebski provides an explanation of how Einstein's ] (of 1915) predicts a simulated tired light effect in clouds of dust, and consequently how it predicts the appearance of an accelerating expansion of space. | |||
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Revision as of 23:26, 8 January 2006
Tired light is the hypothesis that light slowly loses energy as it travels through space. Since a decrease in energy corresponds to an increase in wavelength, this effect would produce a redshift in spectral lines that increases with the distance of the source. It was originally postulated in 1929 by Fritz Zwicky as an alternative to the standard interpretation that the redshift is caused by expansion of the universe. Most physicists and astronomers do not believe that such an effect can account for cosmological redshifts.
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