Quantitative Comparison of Proposed Redshift Mechanisms

L. Marmet

2008 April 10^th

This table summarizes the various mechanisms proposed to explain the observed redshift of various extragalactic objects.Therefore it is important to know the size of each effect. The following table describes these mechanisms, under which conditions they are applicable and the strength of the effect. They are listed in decreasing order of the strength. Note that some of these theories have inconsistencies, e.g. Paul Marmet's redshift mechanism does not conserve photon angular momentum. But they are listed here for the quantitative predictions they give.
Because the observations of redshifts are so varied, it is likely that more than one mechanism is at play. However, because different physical mechanisms have a large scatter in strengths, I expect that only one, maybe two, dominant mechanisms will provide the explanation for the redshift. Note that many theories below have adjustable parameters to try to match the currently observed redshift (e.g. density of neutral atoms, plasma density, etc...). The exact strength is unknown in many cases.

In the following:
"Exponential" implies an exponential decrease of the energy of the photons as a function of distance,
"Raman" implies that the interaction of light with the medium leaves the medium in a different quantum state (rotational, vibrational, or electronic),
"Thermodynamical" implies that the interaction of light with the medium leaves the medium at a different temperature (via momentum exchange),
"L" implies that the effect depends on the propagation distance,
"r" implies that the effects depends on the density of the intergalactic medium (matter, atoms, ions, electrons, etc.).

Name of the redshift	Reference	Description	Strength in terms of a Doppler velocity

Gravitational "Drag"	Fritz Zwicky	Photons passing near a mass are deflected. They transfer momentum and energy to the mass. The photon changes it's energy and therefore it's frequency. The masses are assumed to be independent of each other, but in reality they are coupled by gravitational forces. The correct theory would have to be worked out in terms of absorption of graviational waves. [ r, L / Exponential, Thermodynamical]	1800 km/s/Mpc (assuming 2×10^-24 kg/m³)
Cosmological	Edwin Hubble	The metric expansion of space increases the wavelength of the light over time. This effect is present everywhere in the universe. [L / Relativistic]	71 km/s/Mpc
Dispersive Extinction	Ling Jun Wang	The dispersive scattering and absorption of starlight by the space medium causes a shift of Gaussian lines. No mention of which interstellar gas causes the absorption. Effect is assumed to match the strength of the Cosmological model. Frequency shift Dl/l is not independent of l. [ r, L / Exponential]	71 km/s/Mpc (assuming a certain density of dispersive medium)
Plasma	Ari Brynjolfsson	Collective interaction between many electrons in a plasma and a photon, resulting in a Doppler-like energy loss redshift and heating of the plasma. The theory requires a hot, low density, plasma. Explains the redshift on the sun's limb. [ r, L / Thermodynamical]	63 km/s/Mpc (205 electrons/m³)
Intrinsic	Halton Arp/ Jayant Narlikar/ Fred Hoyle	The mass of matter increases with the square of it's age. Since the spectroscopic redshift varies inversely as the mass, the observed redshift depends on the age difference between the observer and source. Narlikar found the solution m = at² to the generalized equations of general relativity. The effect explains particularily well the redshifts of quasars. Also, the speed of light makes distant galaxies appear younger. Frequency shift Dl/l independent of l. [Relativistic]	c × 39 km/s/Mpc or 12 km/s/Myear
CREIL	Jacques Moret-Bailly	Transfer of energy between higher and lower frequency light through interaction with the Raman polarizability of the medium. Dependent on the specific atomic species and the temperature of the gas. Coherent effect, no blurring of images. Needs incoherent light, low pressures, and the gas must have Raman transitions in the radio frequency range. Infinitesimal frequency shifts add along the light path resulting in a shift smaller or larger than the Raman frequency. Frequency shift Dn/n is independent of n. [ r, L / Exponential]	23 km/s/Mpc (assuming 10000 H₂⁺/m³, 3K)
Secondary emission energy loss	Paul Marmet	The photon momentum produces a polarization of the atom. This polarization causes the atom to emit a small amount of energy before the incident photon is re-emitted with a small energy loss. Dependent on the polarizability of the atoms (or ions) in the intergalactic medium. Not very sensitive on the specific atomic species. Does not work at high density due to the increased collective mass of the medium. Explains the redshift on the sun's limb. Frequency shift Dl/l independent of l. [ r, L / Exponential]	12 km/s/Mpc (assuming 10000 H-atom/m³)
Wolf Effect	Dan James	Coherent effect resulting from the coupling of two partially coherent sources. May explain some features encountered in quasars, but cannot account for the majority of observed shifts of extra-galactic objects. Dependent on the density for a shift larger than the linewidth of the radiation. [ r / Thermodynamical?]	Not available
Thermalization	Charles Gallo	"Hot" radiation thermalizes with the "cold" intergalactic medium. No model is given for the interaction. [ r, L / Exponential, Thermodynamical]	No model
Finlay-Freundlich hypothesis	Finlay-Freundlich	Loss of energy by observed photons traversing a radiation field. No mechanism given except for a proposal that the energy lost reappears as neutrino pairs from the exchange of a graviton between two photons. [L / Exponential]	Not available
Compton Effect	John Kirien	Light scattering on free electrons loses energy. Scattering process changes the direction of the light, therefore remote galaxies could not be imaged. [ r, L / Exponential]	Not applicable