Is Infinity Real?

I can certainly without contradiction describe a universe infinite in space and time. Consider a universe with one spatial dimension, and let it contain a single object which is at point x in space at time t (and hence has a velocity of 1 in appropriate units). Here we have infinite space, infinite time, infinite causality --- and no internal logical contradictions.It follows, does it not, that these infinities cannot be disproved a priori, since that could be done only by identifying a logical contradiction existing within all such hypothetical systems. So that removes such questions from the domain of philosophy and puts them in the domain of science --- which is not to say that scientists can or ever will answer them, only that if they can't it's no use asking a philosopher.

I guess that's why slevesque said "if the premises are true".

Yes, but why not?If science has taught us anything, it's that we can't rule stuff out a priori just 'cos it makes our little human brains boggle.Think of time as being like space, and imagine viewing it sub specie aeternitatis --- a God's-eye view if you will. From that point of view, wouldn't it look even odder if it just started at some point?

In this analogy, what would space represent?Surely it is the passage of time which is like moving through space, and time itself is like space. I think it would be like saying that there was an infinitely long line embedded in the universe.

In that case we are not in disagreement.If we say that passage of time is like passage through space, then to the extent that this is true and meaningful (and I have my doubts about that) we have to say that time is the analog of space. No, it doesn't. There is no way in which this relates to you or me personally. The proposition that past time is infinite does not conflict with the statement that I was born in 1974 any more than the proposition that 1973 existed conflicts with that same statement. Why would it?The proposition that the past is infinite does not contradict the proposition that certain specific things had beginnings.

What if they all move at the same time?

No-one said it did.