Cosmology: time begins (Introduction)

by dhw, Monday, May 26, 2014, 20:40 (3620 days ago) @ David Turell

Dhw: If we take [time] as meaning the sequence of before/now/after, or past/present/future, you and I cannot say time began with the big bang.-DAVID: I must say that our concept of time began after the Big Bang. Note the following. Before the big bang is unknowable:-https://medium.com/starts-with-a-bang/92e02ca82f7f-You've explained "our concept of time" as "we measure time by a succession of events". Since we humans cannot measure anything unknown to us, of course that particular concept began after the BB, but that doesn't mean no events before the BB, and therefore no time. You might as well argue that since God's existence is unknowable, there is no God! If we don't know whether there were events, we don't know whether there was time. The website you've quoted contradicts you:
 
QUOTE: In fact, the particulars of this [data concerning the temperature of the universe] tell us that not only did time not begin at the Big Bang, but that we know what happened before the Big Bang: there was a period of cosmic inflation, where a tremendous amount of energy intrinsic to space itself dominated the Universe, and it expanded exponentially quickly at a fantastically large rate! -The bold is the author's, not mine. "Before the BB" is slightly misleading, because later he qualifies it with "a little bit". However, he does not restrict the amount of time involved:-QUOTE: Image generated by me, of the scale of the Universe (y-axis) vs. time (arbitrary units).
It tells us that rather than a singularity at "t=0", or where the Big Bang occurred, it tells us that [sic] the Universe existed in an inflationary state, or a state where it was exponentially expanding, for an indeterminately long amount of time. [/b]-Again, the bold is the author's, not mine, and he goes on to ask (among other questions): "did the inflationary state last forever going backwards?" Of course we don't and can't know, though he says: "It's even possible that time is cyclical, and that the cycles change with each iteration!"-Final quote: "But even though we can trace back our cosmic history all the way to the moment of the Hot Big Bang, and even before that (a little bit) to the epoch of cosmic inflation, that's where our knowledge ends. So thousands of years later, we're right back to where we started."-On the assumption that you would regard inflation as an event, this can hardly be said to support the claim that time itself began with the BB. He is making the same point as me: we do not and cannot know when time began.