Here's my argument:
1. In our experience, every moment of spacetime is caused by a previous moment of spacetime.
2. There are two concievable options: either (a) it is possible that moments of spacetime can be uncaused/caused by something nonspatiotemporal or (b) it is impossible for moments of spacetime to be caused by anything except previous spacetime.
3. On the hypothesis that (b) is true, it is 100% likely that we would observe (1). On the hypothesis that (a) is true, there must be less than a 100% chance that we would observe (1) because on the (a) hypothesis, spacetime can be caused by nonspatiotemporal things or uncaused altogether.
4. We should prefer the hypothesis that does the best job of predicting the data, all else held equal.
Conclusion: From 3 and 4, spatiotemporal moments are probably always caused by previous spatiotemporal moments. The only way this can happen is if the universe is eternal, or if something like Quentin Smith's scenario for a self-caused universe is correct.
2 comments:
Normal concepts of spacetime break down at the instant of the Big Bang, because of quantum uncertainty. It follows that if that particular moment was caused by something other than previous moments, we would not expect that fact to show up in our experience. We are not the sort of organism that could exist at that moment.
Hi David,
"Normal concepts of spacetime break down at the instant of the Big Bang, because of quantum uncertainty."
Could you clarify? Do you mean the big bang singularity or the first moment of expansion? If the former, my understanding is that most cosmologists these days don't believe in a singularity. If the latter, I don't doubt that the first moment of expansion would be different because of the fact that we lack knowledge on quantum effects. I don't see this as defeating my thesis, because that moment could have been caused by a previous moment, or it could be that the first moment is infinitely divisible as Quentin Smith suggested (see the article I linked to in the post).
Sincerely,
Ryan
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