Tired Light
This Natural Philosophy wiki page disputes content found on Wikipedia page wikipedia:Tired light
| Scientific Theory | |
|---|---|
| Name | Tired light |
| Type | Alternative explanation of the cosmological red shift |
| Author(s) | Fritz Zwicky (1929); variants by many later authors |
| Keywords | Cosmology, red shift, static universe, photon energy loss, Hubble's law, Big Bang, intrinsic redshift |
| Year | 1929 |
Tired light is the general name for a family of proposals in which the red shift of light from distant galaxies is caused by a gradual loss of energy by photons as they travel through space, rather than by a recession of the galaxies or an expansion of space. Because a photon's energy is proportional to its frequency, any process that steadily drains energy from light over great distances would lengthen its wavelength — that is, shift it toward the red — by an amount that grows with distance, reproducing the linear redshift–distance relation (Hubble's law) within a static, non-expanding universe. In mainstream physics and astronomy tired light is regarded as an obsolete and falsified idea; on this wiki it is documented as a serious alternative to the expanding-universe interpretation that underlies the Big Bang, and a substantial body of supporting and reviving work is collected in the section below.
The basic idea
The observed fact that light from distant galaxies is shifted toward longer (redder) wavelengths in proportion to their distance is not in dispute. What is disputed is its interpretation. In the standard cosmology the redshift is read as a Doppler-like effect of galaxies receding from us as space expands. Tired-light models instead attribute the redshift to some interaction between the traveling photons and the intervening medium — or to a novel property of light propagation itself — that removes a small, fixed fraction of a photon's energy per unit distance. Assuming an exponential decline of energy with distance yields, for small redshifts, exactly the linear relation between redshift and distance that Hubble measured, but without requiring the universe to be expanding.
A tired-light interpretation therefore removes the need for a beginning of the universe in a hot, dense state, and is naturally associated on this wiki with static-universe and steady-state cosmologies and with the broader critique of the Big Bang.
History
The idea dates to the very origin of the expanding-universe controversy. In 1929, the same year that Edwin Hubble published the redshift–distance relation, the Swiss-American astronomer Fritz Zwicky proposed in the Proceedings of the National Academy of Sciences that photons might lose energy on their way to us through interaction with matter — an effect he compared to a gravitational analogue of the Compton effect. The evocative name "tired light" was coined a few years later, in the early 1930s, by Richard Tolman.
During the 1930s several other physicists advanced related energy-loss or static-universe schemes, among them John Q. Stewart, William D. MacMillan, and the Nobel chemist Walther Nernst. Through the middle of the twentieth century tired light remained one of the recognized alternatives to the expanding universe, discussed alongside the steady-state model. After the detection of the microwave background in 1965 and the accumulation of other observations, mainstream cosmology set tired light aside; it has nonetheless continued to be developed by a minority of researchers, several of whose works are catalogued on this wiki.
Proposed mechanisms
Tired-light authors have suggested many different physical causes for the supposed energy loss, including:
- Scattering by matter — Compton-type or other scattering of photons by free electrons or by particles of an intergalactic medium.
- Photon–photon and photon–field interactions — interactions of starlight with ambient radiation or fields en route.
- Gravitational drag — a cumulative gravitational interaction between photons and the masses distributed through space.
- Inertial induction — a velocity-dependent inertial interaction, developed on this wiki by Amitabha Ghosh.
- Plasma and "new tired light" effects — energy loss to a tenuous intergalactic plasma, in which the recoil of electrons is claimed to redshift the light while re-emitting the absorbed energy at radio wavelengths (a proposed source of the microwave background).
Because these mechanisms make differing quantitative predictions, they are not a single theory but a class of theories sharing the premise that redshift measures energy loss over distance rather than recession.
Mainstream objections
In conventional cosmology tired light is considered refuted, and its difficulties are frequently cited. The principal objections are:
- Blackbody form of the microwave background — a scattering mechanism that gradually degrades photon energies would generally distort a thermal (blackbody) spectrum, whereas the cosmic microwave background is observed to be very nearly a perfect blackbody.
- Surface-brightness (Tolman) test — in a static tired-light universe the surface brightness of galaxies should not fall off with redshift in the way expected for an expanding universe; the observed dimming is usually read as favoring expansion.
- Supernova time dilation — the light curves of distant Type Ia supernovae appear stretched in time in proportion to (1 + z), as expected if distant clocks are slowed by expansion; a simple tired-light model predicts no such stretching.
- Image sharpness — most scattering mechanisms would blur the images of distant objects far more than is observed.
Several of these objections are contested by tired-light authors, and the wiki works below address the supernova, microwave-background, and mechanism questions directly.
Tired light on this wiki
The community of the John Chappell Natural Philosophy Society, which maintains this wiki, has produced and collected a considerable literature that develops, tests, or defends tired-light cosmology as an alternative to the expanding universe. Related material is indexed under Category:Cosmology.
Reviews and defenses
General cases for reconsidering the hypothesis are made in On Reviving Tired Light, while the countervailing view is represented in A Case Against Tired Light and the Big Bang. The confrontation with supernova data — the objection most often held to be decisive — is taken up in Tired Light and Type Ia Supernovae Observations.
Proposed mechanisms
Specific physical mechanisms are worked out in A Possible Tired-Light Mechanism and, from a gravitational standpoint, in Velocity-Dependent Inertial Induction: A Possible Tired-Light Mechanism by Amitabha Ghosh. A quantum-mechanical proposal is examined experimentally in Laboratory-Scale Test of de Broglie's Tired-Photon Model.
"New tired light" and laboratory tests
A distinct plasma-based development, often called new tired light, is represented by Electron-Spin-Reversal Noise in the Gigahertz and Terahertz Ranges as a Basis for Tired-Light Cosmology, Intrinsic Plasma Redshifts Now Reproduced in the Laboratory: A Discussion in Terms of New Tired Light, New Tired Light Correctly Predicts the Redshift of the CorBor Galaxy Cluster, and Gamma-Ray Lines of the X-Class Solar Flare of July 23rd, 2002 Provide Direct Evidence of New Tired Light. These works argue that a tired-light interaction can be, and has been, reproduced in the laboratory and that it also accounts for the microwave background.
Related topics
Tired light is part of the wider dispute on this wiki over the interpretation of the red shift and the reality of cosmic expansion. See the criticism sections of the Big Bang article, the work on intrinsic and quantized redshift associated with Halton Arp, and the general survey of Cosmology.