As I understand it, you can't see beyond the Cosmic Microwave Background Radiation because the plasma of the early universe was opaque to electromagnetic radiation. What if you had a "neutrino telescope" with sufficient resolution? Would you be able to observe the primordial universe from before recombination?


Yes, but it should be stated that the cosmic neutrino background is expected to be very cold and very difficult to see. Also, note that when temperatures approach the electroweak unification scale, the electroweak force will treat electrons and neutrinos identically, and the universe will become opaque to neutrinos.

  • $\begingroup$ When exactly did the electromagnetic and weak forces separate? Within the first second or so after the Big Bang? If so, neutrinos do in principle provide a window into times well before the 380 ky it took for photons to be able to propagate, and that's a lot of time. $\endgroup$ – Emilio Pisanty Aug 5 '14 at 21:18
  • $\begingroup$ @EmilioPisanty: no doubt there, electroweak energies are certainly several orders of magnitude higher than ionization energies. I was just pointing out that you can't go all the way back to the big bang, or, say, directly probe what we expect to be the inflationary epoch. $\endgroup$ – Jerry Schirmer Aug 5 '14 at 21:24
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    $\begingroup$ OK. Still, the language makes it sound like it's only a minor improvement. You would definitely be able to observe a lot of physics in the OP's 'universe before recombination'. $\endgroup$ – Emilio Pisanty Aug 5 '14 at 21:27
  • $\begingroup$ Indeed, from before the epoch of nucleosynthesis for instance. $\endgroup$ – ProfRob Apr 10 '20 at 12:31

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