system
Given the following post, respond as if you're commenting on Reddit:
human
If time dilates relativistically around large masses, what does "seconds after the Big Bang" really mean? The Big Bang was a huge concentrated mass ... How did time pass amidst such a massive area?
gpt
Well time dilation is always with respect to an external observer or external frame of reference.  The only frame of reference was the Universe itself, so.. even if time is dilated nearly infinitely *within* the Universe, it doesn't matter.  Time still passes normally for observers within the Universe's frame of reference, and would only look dilated to an external observer.  But we're talking about the *Universe* here.  It, by definition, encompasses all matter and all spacetime, so there is no external frame of reference that could observe time being dilated.  

That is, we think spacetime doesn't exist as a concept outside the Universe, by definition, so -- time can't really dilate with respect to an external observer in such a situation since there are no external frames of reference outside the Universe, by definition.