If the scale factor $a(t)$ is 0 at the start of the universe, what would the scale factor at the end of the Planck epoch (t=Tp) be?

  • $\begingroup$ In the standard Friedmann-Robertson-Walker Universe, the scale factor at the start of the Universe is $a=0$. $\endgroup$ – Virgo Nov 5 '16 at 21:27
  • $\begingroup$ Oh, ok. What would it be, in theory, at one Planck time? Surely, it'd be near 0, obviously. Don't seem to be pushy, btw lol. $\endgroup$ – Ringo Hendrix Nov 5 '16 at 21:35

The temperature of the CMB today is about 3K. While the Planck temperature is about $10^{32}$ K. Ignoring some minor changes due to some out of equilibrium phases, $T\propto a^{-1}$. We can therefore conclude at the Planck era $a\sim 10^{-32}$.

| cite | improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.