A seemingly obvious explanation for redshift in light that has traveled distances on the order of hundreds of millions or billions of light-years would be a slight loss of energy resulting in redshift. The loss could come, for example, from some quantum event resulting in very occasional loss of a photon, or from some other phenomena. Given the ubiquitous appearance of entropy in nature, there seems no reason to expect light would propagate over extreme distances without some degrading.
If entropy were the cause of redshift it would be expected that the amount of redshift would be based on the distance traveled. Since this conforms with the detected data, it seems this explanation, whatever the objections may be, is a reasonable candidate as the cause of detected redshift. At first glance, this would seem a better candidate than a conjectured but undetected new entity such as “dark energy”.
This is such an obvious explanation for redshift, I am assuming that it has been advanced before, likely numerous times. I am interested in getting up to speed on arguments for or against entropy as an explanation for redshift.
probably not, and there are several reasons for this. Redshift, especially as observed in the context of an expanding universe, is primarily explained through the Doppler effect and the cosmological principle of an expanding universe, not through entropy.
1. Cosmological Redshift: The observed redshift in distant galaxies is usually attributed to the expansion of space itself, as per the standard cosmological models. This expansion stretches the wavelength of light, causing the observed redshift. This explanation is consistent with General Relativity and the observations of the Cosmic Microwave Background.
2. Entropy and Photon Loss: The idea that entropy could cause a loss of energy in photons over vast distances is not supported by quantum electrodynamics, the theory that describes the behavior of light. Photons in a vacuum do not lose energy through interactions in the way that particles in a thermodynamic system might.
3. Dark Energy: Dark energy is a different concept, primarily invoked to explain the observed acceleration in the expansion of the universe, rather than the redshift of light from distant galaxies. Its nature is still a major unsolved problem in physics.
4. Consistency with Observations: The redshift-distance relationship (Hubble's Law) observed in the universe aligns well with an expanding universe model. An entropy-based model would need to consistently match these observations and offer predictive power to be considered a viable alternative.
Harry
Thanks for taking time to put a well-reasoned answer up. I agree that the doppler effect is the generally accepted explanation for cosmological redshift.
The problem with invoking the doppler effect to explain redshift is that it has led to the expanding universe model, with the need to explain the presumed acceleration of the expansion. This has led to the conjecture of the existence of “dark energy” which is supposed to be gravitationally repulsive.
The only empirical evidence I have seen for dark energy is the cosmological redshift. Being a non-specialist, that seems a pretty radical and improbable explanation for something that could possibly be explained by other phenomena.
For example, Halton Arp in his paper Intrinsic Redshifts in Quasars and Galaxies (https://www.haltonarp.com/articles/intrinsic_redshifts_in_quasars_and_galaxies.pdf) argued:
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There are three kinds of evidence for the existence of non-velocity redshifts:
1) Statistical association of objects having much different redshifts. (See e.g. analysis by C. Fulton (Fulton & Arp 2009) of the 2dF deep field, and Burbidge & Napier (2009).)
2) Interaction between objects of different redshift (including high redshifts aligned across active galaxy nuclei).
3) Quasars occurring preferentially at certain specific redshifts.
The latter precludes redshifts caused by recessional velocity because it would require matter distributed in shells and receding velocities in discrete steps.
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My thinking is that if cosmological redshift is going to be explained by imagining exotic phenomena like dark energy, perhaps it is worthwhile to consider other unproven phenomena that is more in line with phenomena we can observe.
Entropy is universally observed. Light is an anomaly in that over the distances and time we typically can measure, we see no evidence of entropy in the propagation of light. However, cosmological redshift could be considered evidence for the entropy of light, as there is redshift detectable in light that we assumed has traveled hundreds of millions or perhaps billions of light years.
I realize this is not conventional thinking. But presenting the hypothesis of light entropy seems a more reasonable jump of known phenomena to explain a mystery, than to invoke something complete radical to our experience, such as “repulsive gravity”. And dark energy is only the tip of the iceberg of, in that phenomena more exotic than dark energy --such as quantum fluctuations birthing bubble universes, cosmic inflation, and so on—have been imagined to explain the initiation of an expanding universe.
Entropy of light seems like an obvious, and less exotic candidate, to explain cosmic redshift. I am hoping to find the trail left by any who may have traveled this way before.
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