RE: Why the universe is most likely not infinite – Part 5: Popular argument against infinity
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Very interesting.
This argument does not work quite as well as hoped, but the Big Bang is also not a proof of infinity and at least rules out an infinitely old, infinitely large steady-state universe.
This would be the case if you make the assumption that the universe started with the Big Bang. However, the Big Bang is not the origin of the universe, but the earliest state that we have evidence of. It is like the highest point of a mountain, which is not the beginning of the mountain, but the place where it starts to descend. The Big Bang describes how the universe evolved from an incredibly dense and tiny point, but it doesn't account for the laws of physics and other things. More and more cosmologists are moving away from the idea that the Big Bang was an absolute beginning and consider it a sort of "first moment of time", as Sean Carroll puts it.
I would say that this argument reminds me of another argument that apologists use to defend the existence of God using science to make philosophical points, such as in the Kalam cosmological argument. William Lane Craig is one of the main defenders of that argument but he was was critiziced by top physicists and mathematicians such as Sean Carroll, Roger Penrose, Carlo Rovelli, Adrian Moore and others on the plausibility that the universe may be eternal and and therefore, actual infinities may exist. The documentary is on Youtube.
Do you think the universe can be eternal? This, I think, brings many aporias.
If the past is infinite (rather uninitiated), we can go infinitely backwards, right? But if the past is infinite, it would take an infinity of time to elapse (the past), wouldn't it? But an infinite time would never end, precisely because it is infinite. However, the past has already end because we are, obviously, in the present. So, how can the universe be eternal?
Yeah, I'm pretty sure that's answered in the documentary too. You should watch it. There are several ways to approach it.
Given that there will be an infinite number of present times, then it is logically conceivable that an infinite amount of time has elapsed for each one of them. The limit of the past present time doesn't have to be the present time that you want to pick up, because that would be confusing and switching the necessary condition with the sufficient condition. I know, it gets confusing, that's how the logic works. This is only by resorting to Logic and Philosophy, not Physics. You can watch the documentary for more information.
I don't think I'm going to watch it. But thanks for the recommendation.
I think this does not solve the problem, but multiplies it. As I see it, an infinite time can never end, precisely because if it ends it would have an end, i.e., it would not be infinite.
If we were to accept, just by imagination, that infinite time could elapse, then we could go back to the past, elapse infinite time, and arrive at the "beginning" of the universe. Does that make sense? Just as infinite time could elapse into the present, we could also do the opposite and travel into the past.
But then again, the infinite is that which has no end, and I don't see how anything infinite could end.
Thanks for your attention. I will take the video into consideration.
Cheers!
We're never going to reach the end of the beginning of the infinite time. It's just a concept, just like the sum of infinites or a Zenonian progression, that's why I said it is logically conceivable. To resolve that paradox, for example, you need to take into account that the size of the set of infinite present times is also infinite, it's just that today can't be the last moment, there are infinite present times. This makes more sense in the context of the tenseless theory of time, where there's no difference between the past, present and future. This issue is more complicated than it looks and the paradox you're raising is well known. Bear in mind that a finite time also creates counter-intuitive situations. For example, what was there before the beginning?
Sure, I'm glad you're interested in the topic. If you want to hear it from leading physicists and philosophers instead of me, then you should watch it.
Why do you say there are infinite present times? I am not a fan of Ockham's razor, but it seems much simpler to say that there is only one present time that does not end, than to say that there are infinite present times that end one after the other. Am I missing something?
It's interesting. As I see it, one could also say that there is only the present, and that it is eternal.
Yes, I am also aware of some of the obstacles that this brings. Some, like creationists, would argue that something of a different nature than the universe pre-existed. But it is a tricky issue.
I think most of these paradoxes can be solved if we change our perception of time. And if we stop seeing time as something linear. As you say, a tenseless time takes a step forward in this direction, I think.
Paradoxes, in general, teach us, I think, that we are considering things in an inadequate way, and that therefore, we must employ another path. These are not unsolvable problems, but just an indication that something needs to change in our approach.
Thanks and regards!
It used to be common to think like this in the past but now we know better.
Yes, it is philosophical, but it is also logical. Now, with the advent of physics, it's also scientific. There are models of the universe with and without a beginning. Both types are mathematically consistent and empirically adequate. We just don't know which model is the right one, if any. All of this is covered in the documentary.
Thank you.
good point, at least we have good evidence of the Big Bang, but we have no idea what happened before the Big Bang and why it happened in the first place, but those questions are meta-physical, pure speculation, non-scientific in the sense that we cannot test theories that are outside of our universe.
I agree, but it's still mathematically consistent. Many cosmologists regard the Big Bang as an open boundary, so there are both models of the universe with a beginning and models of eternal universes. Also, as a general principle, metaphysics should conform to physics, so it's not unscientific necessarily. Anyway, the main point was that actual infinities might exist and it's a widely accepted view among the experts in the relevant fields. Thanks for bringing up this topic.