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Could the universe be filled with photons with a wavelength of the size of the universe? Do such photons exist?

If so, what would be their equation of state?

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  • $\begingroup$ Have you tried to do a back-of-an-envelope-estimation? $\endgroup$ – Qmechanic Feb 5 at 20:28
  • $\begingroup$ For the equation of state of real photons, w=1/3. But this is only true if such real photons exist... $\endgroup$ – frauke Feb 5 at 20:48
  • $\begingroup$ Do you have any reason to think that that equation of state holds for photons of some frequencies and not for others? $\endgroup$ – G. Smith Feb 5 at 22:11
  • $\begingroup$ Yes. Claiming that a photon exists with a wavelength of the size of the universe is not self-evident. It is also questionable whether wavelengths larger than the size of the universe exist. They cannot be measured - so they look almost unscientific. That is the reason for the question. $\endgroup$ – frauke Feb 6 at 5:29
  • $\begingroup$ You asked: If they exist, what would be their equation of state? Their possible nonexistence has nothing to do with this question. $\endgroup$ – G. Smith Feb 7 at 3:37

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