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Rainbow gravity (or "gravity's rainbow") is a theory that different wavelengths of light experience different gravity levels and are separated in the same way that a prism splits white light into the rainbow. This phenomenon would be imperceptible in areas of relatively low gravity, such as Earth, but would be significant in areas of extremely high gravity, such as a black hole. As such the theory claims to disprove that the universe has a beginning or Big Bang, as the big bang theory calls for all wavelengths of light to be impacted by gravity to the same extent. The theory was first proposed in 2003 by physicists Lee Smolin and João Magueijo, and claims to bridge the gap between general relativity and quantum mechanics. Scientists are currently attempting to detect rainbow gravity using the Large Hadron Collider.

Background

Rainbow gravity theory's origin is largely the product of the disparity between general relativity and quantum mechanics. More specifically, "locality," or the concept of cause and effect that drives the principles of general relativity, is mathematically irreconcilable with quantum mechanics. This issue is due to incompatible functions between the two fields; in particular, the fields apply radically different mathematical approaches in describing the concept of curvature in four-dimensional space-time. Historically, this mathematical split begins with the disparity between Einstein's theories of relativity, which saw physics through the lens of causality, and classical physics, which interpreted the structure of space-time to be random and inherent.

The prevailing notion about cosmic change is that the universe is expanding at a constantly accelerating rate; moreover, it is understood that as one traces the universe's history backwards one finds that it was, at one point, far denser. If true, the Rainbow gravity theory prohibits a singularity such as that which is postulated in the Big Bang. This indicates that, when viewed in reverse, the universe slowly approaches a point of terminal density without ever reaching it, implying that the universe does not possess a point of origin.

Criticism

There are stringent constraints on energy-dependent speed-of-light scenarios. Based on these, Sabine Hossenfelder has strongly criticised the rainbow gravity concept, stating that "It is neither a theory nor a model, it is just an idea that, despite more than a decade of work, never developed into a proper model. Rainbow gravity has not been shown to be compatible with the standard model. There is no known quantization of this approach and one cannot describe interactions in this framework at all. Moreover, it is known to lead to non-localities which are ruled out already. For what I am concerned, no papers should get published on the topic until these issues have been resolved."

See also

• Steady-state model
• Eternal inflation
• Cyclic model

References

1. Zyga, Lisa (15 January 2015). "Black holes do not exist where space and time do not exist, says new theory". phys.org. Retrieved 28 March 2015.
2. Kestin, Greg (13 Dec 2013). "Universe May Have Been Around Since Forever, According to Rainbow Gravity Theory". NovaNext.
3. ^ Moskowitz, Clara (9 Dec 2013). "In a 'Rainbow' Universe Time May Have No Beginning". Scientific American.
4. Knapton, Sarah (23 Mar 2015). "Big Bang theory could be debunked by Large Hadron Collider". The Telegraph.
5. ^ Slavnov, D. A. (6 July 2012). "Possibility of reconciling quantum mechanics with general relativity theory". Theoretical and Mathematical Physics. 171 (3): 848–861. Bibcode:2012TMP...171..848S. doi:10.1007/s11232-012-0080-z. ISSN 0040-5779. S2CID 85454483.
6. O’Hara, Paul (1 September 2005). "Quantum Mechanics and the Metrics of General Relativity". Foundations of Physics. 35 (9): 1563–1584. arXiv:gr-qc/0502078. Bibcode:2005FoPh...35.1563O. doi:10.1007/s10701-005-6483-z. ISSN 0015-9018. S2CID 15735651.
7. Hossenfelder, Sabine (9 April 2010). "Bounds on an Energy-Dependent and Observer-Independent Speed of Light from Violations of Locality". Phys. Rev. Lett. 104 (14): 140402. arXiv:1004.0418. Bibcode:2010PhRvL.104n0402H. doi:10.1103/PhysRevLett.104.140402. PMID 20481922. S2CID 5755427.
8. Hossenfelder, Sabine (25 March 2015). "No, the LHC will not make contact with parallel universes". Backreaction. Retrieved 17 October 2015.

• Physical cosmology
• Astrophysics theories
• Theories of gravity