[jennyp]

My main objection was that human eyes don't see photons of such low energy, since they are very long-wave. And I never got a convincing answer to why that's not a problem.

What if Adam's eyes were detecting the slower, less-energetic cosmic rays?

[VadeRetro]

What if Adam's eyes were detecting the slower, less-energetic cosmic rays?

If you redshift the spectrum of light we're bathed in now by a factor of, say, 11 million, the solar peak our eyes are tuned to now disappears. There's not enough energy way up there for Adam to see anything with.

[VadeRetro]

What if Adam's eyes were detecting the slower, less-energetic cosmic rays?

Also, I think you mean "longer, less-energetic gamma rays." Cosmic rays are actually massive particles, not photons. All photons have the same speed, the energy difference being in the wavelengths.