# How do we understand time & size in the earliest moments of the universe?

1) I don't know whether this question should belong to this site: please correct me if not.
In the earliest moments of the universe history probably all fundamental forces where indistinguishable: in particular there weren;t any massive particles. This time include the so called electroweak epoch which ended about $10^{-12}s$ after the Big Bang.

How do we understand this time, since when there is no massive particle the notion of time does not make sense?

2) Moreover we often speak about the size of the universe in that period, we say that universe was expanding (in some model like inflation, this expansion was very rapid).

Can we even discuss the size when there is no mass? No mass implies that everything travels with the speed of light and in the world where everything travels with the speed of light I would say that there is no notion of distance either.