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Justifying the Unjustifiable: No Monotonous Cooling of the CMB

Going back in time to the dawn of time (if that has any meaning) is like reading the Book of Genesis backwards. The only problem is that God would need a detailed road map of what he did. As more observations of larger and larger redshifts of the 21-cm line become available more patching up of the standard model is necessary.


According to the party line, redshifts around the epoch of star formation, the abundance of Lyman-alpha photons would induce an increase in their absorption rate. The absorption of the 21-cm signal (often called the "window" on the universe) is expected to be strongest during this period. And the absorption depends on the baryonic temperature.


It is precisely these large absorption features is what EDGES claims to have observed. Instead of finding a temperature of about 6 K, which is what the standard model predicts, it claims that the temperature is much lower, around 3 K, almost the same as the present temperature of the CMB. (See the figure.)

Absirption feature measured by EDGES as a function iof the redshift z. The thick black line is the model fit.

The overall magnitude of the absorption is far greater than should be possible if the baryonic temperature were 6K, as predicted. This calls into question the legitimacy of the Lambda CDM model of the early universe. Lambda is the cosmological constant, which has been made non-constant. This introduces an additional fudge factor called quintessence that makes the cosmological constant vary in time and has been proposed as the "fifth" fundamental force. This is what happens when people run out of ideas and conjure up whatever it takes to make the books balance.


The CDM part of the tile is "Cold Dark Matter", which is some imaginary matter that is around to patch things up when required. The rationale, if it could be called that is given by Loeb, in his book How Did the First Stars and Galaxies Form?


"If there was nothing else in addition to radiation and ordinary matter, then the smoothing process would have had a devastating effect on the progress of life in our Universe. Galaxies like the Milky Way would not have formed by the present time since there would have been no density perturbations on the relevant small scales to seed their formation. The existence of dark matter not coupled to radiation came to the rescue by keeping the memory of the initial seeds of density perturbation on small scales."


Now the same.dark matter is implicated in the excess cooling of the cosmic gas by "scattering off baryons with a cross section of 10^{-21} cm^{2} at a relative velocity of 1 km/s, according to Barkana. This "transforms the 21-cm cosmology into a unique dark matter probe..." The excess 21-cm absorption signal is a "clear sign of baryon-dark matter scattering, since alternative explanations are untenable."


Ruling out alternatives is certainly no way of doing science. It would be better to attribute the cooling to an act of God. Claiming, like Loeb does in his book, that "dark matter is the dominant constituent of the Universe" does not make it so when no one has ever seen it. Attributing a "small electric charge" to dark matter that allows it to interact with ordinary matter is like Einstein's generalization of the velocity dependency of the mass of an electron to all matter because all matter can become charged by adding a "smidgen of charge to neutral matter."


The dip at 78MHz implies that 1 in 6 CMB photons were absorbed by hydrogen at this frequency. The depth factor is twice as big as the standard model predicts. Wouldn't it be wiser to question the standard model than inventing a new force that would cool stars faster than expected? Moreover, while we are questioning the standard model, why not question the origin of the CMB? What on earth--or better the Universe--would give rise to a non-monotonic cooling of the cosmic microwave background? Perhaps the background radiation is really due to starlight, and has nothing to do with our cosmic origin.


It is extremely difficult to refute vacuous statements like those made in the Bible. One has to accept or reject them on blind faith. This can hardly be called science. Rather, what is objectionable on scientific grounds is statements like "In thermodynamics, pressure is derived from the deficit of energy per unit new volume." This leads to a vacuum pressure equal to the negative of the vacuum's rest energy density.


This statement is found in Loeb's book, where he tries to justify a negative pressure for a constant vacuum density. In his words, this occurs when "opening up a new volume increment one gains energy (rest energy) instead of losing energy." A good course in thermodynamics is recommended to alleviate any concerns about the existence of a negative pressure which creates a "repulsive gravity" and drives the expansion of the Universe. If such gross, elementary, errors are made, how can one have faith in the bigger claims in a book that seeks to provide the answer to How did the First Stars and Galaxies Form?

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