# The Scale Factor During The Planck Epoch

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?

• In the standard Friedmann-Robertson-Walker Universe, the scale factor at the start of the Universe is $a=0$. – Virgo Nov 5 '16 at 21:27
• 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. – 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 $a\sim 10^{-32}$.