2 votes

If every cubic metre of space contained roughly 10^41 photons, each with a wavelength of 88 billion light years, would it be possible to detect them

If there was that much EM radiation it would drastically alter the expansion of the universe. Normal matter dilutes in the way you would expect as the universe expands i.e. if the scale factor doubles ...
John Rennie's user avatar
1 vote
Accepted

Can we measure temperature in an isothermal Universe?

Recording an experimental result generates entropy. In a perfectly isothermal universe at maximum entropy, this is impossible. Thus no experiment of any kind is theoretically possible in such a ...
John Doty's user avatar
  • 20.2k
1 vote

Can we measure temperature in an isothermal Universe?

If by "isothermal universe" you mean the state like in the "heat death of the universe", then no, because there is no thermometer, only chaotic, feature-less, gas-like system. But ...
Ján Lalinský's user avatar
1 vote

Why are the distances in real space and Fourier space inverses of each other?

There are many possible answers to this question. The duality (large wavenumber = small lengthscales) is very deeply rooted in the Fourier analysis with many applications, see for example Heisenberg's ...
Fabian's user avatar
  • 1,979

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