(2) The microwave “background” makes more sense as the limiting temperature of space heated by starlight than as the remnant of a fireball.
The expression “the temperature of space” is the title of chapter 13 of Sir Arthur Eddington’s famous 1926 work, [[4]] Eddington calculated the minimum temperature any body in space would cool to, given that it is immersed in the radiation of distant starlight. With no adjustable parameters, he obtained 3°K (later refined to 2.8°K [[5]]), essentially the same as the observed, so-called “background”, temperature. A similar calculation, although with less certain accuracy, applies to the limiting temperature of intergalactic space because of the radiation of galaxy light. [[6]] So the intergalactic matter is like a “fog”, and would therefore provide a simpler explanation for the microwave radiation, including its blackbody-shaped spectrum.
Such a fog also explains the otherwise troublesome ratio of infrared to radio intensities of radio galaxies. [[7]] The amount of radiation emitted by distant galaxies falls with increasing wavelengths, as expected if the longer wavelengths are scattered by the intergalactic medium. For example, the brightness ratio of radio galaxies at infrared and radio wavelengths changes with distance in a way which implies absorption. Basically, this means that the longer wavelengths are more easily absorbed by material between the galaxies. But then the microwave radiation (between the two wavelengths) should be absorbed by that medium too, and has no chance to reach us from such great distances, or to remain perfectly uniform while doing so. It must instead result from the radiation of microwaves from the intergalactic medium. This argument alone implies that the microwaves could not be coming directly to us from a distance beyond all the galaxies, and therefore that the Big Bang theory cannot be correct.
None of the predictions of the background temperature based on the Big Bang were close enough to qualify as successes, the worst being Gamow’s upward-revised estimate of 50°K made in 1961, just two years before the actual discovery. Clearly, without a realistic quantitative prediction, the Big Bang’s hypothetical “fireball” becomes indistinguishable from the natural minimum temperature of all cold matter in space. But none of the predictions, which ranged between 5°K and 50°K, matched observations. [[8]] And the Big Bang offers no explanation for the kind of intensity variations with wavelength seen in radio galaxies.