Note that I’m not asking whether or not it’s compatible with the Big Bang model. There are other models out there that posit a steady state, or a series of big bangs, etc. So it’s not does it happen to be true, but is it even logically possible. The reason I ask is someone wrote the following comment at another website:
This doesn’t seem to make sense to me. I brought up the point that there are infinite integers, and we can point to any particular one just fine. And he made the point that it was possible to jump directly to that integer, but one could not count up to that integer starting from negative infinity. I don’t see why not - if there was an infinite past then I would have already been counting forever without having started at a particular point. But that just seems like mumbo jumbo to me to explain away his discomfort with the idea of an infinite past. What’s the scoop? Is there some math that can defeat this? Is this some kind of Zeno’s paradox sort of nonsense?
It’s certainly hard to grasp intuitively, but I don’t think there’s any logical problem. Almost all of the laws of physics are time-symmetric, and a universe which is infinitely old and with ever-increasing density is just as mathematically valid as one which has ever-decreasing density and which will last forever (like, say, the one we believe we live in). In such a universe, life (at least, as we know it) would be impossible until a short time before the end (say, hundreds of billions of years) when matter had gotten dense enough for stars to form.
Doesn’t seem any more illogical than the notion of finite time – what came before it? Time’s tough to discuss with regular vocabulary.
And, yeah, I’m pretty sure somebody smarter re: infinite sets could demonstrate that it isn’t a logical impossibility per se, especially if time is treated as a dimension.
Bolding mine. Enough time elapsed since when? Whenever you talk about “time elapsed”, you have to talk about a starting point for time. In a Universe with an infinite past, no such natural starting point exists.
It seems a logical impossibility to me, for exactly the reason noted (which is not a notion that originated with me or that website). How much time will need to have elapsed before we get to the present point in time? An infinite amount, we would never reach the present. In fact, the entire concept of “reaching” any point on a time-line that regresses infinitely is a non sequitur.
You needn’t talk about the time elapsed since a prior point; in fact, that’s irrelevant. Think only of the total amount of time that needs to have passed before we would experience the present moment. We never would “reach” the present. And yet, here we are.
That assumes that we are actually moving in time, while as I understand it relativity can be argued to portray a universe where movement within time is an illusion. In other words, when (for lack of a better word) the universe came into being the past and future were already there in their entirety.
Also, I don’t see why infinite time is any more illogical than infinite space. Why do people focus on time so much in these arguments?
That’s the only way I could envision overcoming the illogical nature of the infinite regress–establishing that time as we typically understand it is an illusion. IOW, there is no logic to overcome, time is a mirage. But if it works as we have typically perceived it to, an infinite regress is a non sequitur.
An infinite space seems illogical too. If everything in space requires a causal relationship with something else to bring it into its current state (which includes its place in the universe), then it’s the same non sequitur. If we suppose otherwise, than an infinite space is possible–it’s not subject to the same logical constraint as time.
Unless by “space” you mean an infinite “nothingness” which seems, frankly, the only thing that is perfectly logical based on what we know. There should be nothing. And yet, here we are.
I’m with you—this is why I don’t believe in causality. I think it’s no more logical to say one event causes another than it is to say that the apex of a cone causes the base.
Then again, I’m one of those baby-with-the-bathwater whackjobs who subscribes to the idea of the block universe.
I can certainly understand why folks don’t want to join us, but it does explain a lot. All these infinite-regress arguments take causality as an unstated given, IMO.
Logic is a human made construct that flatters human intuitions and as far as I can see has zero relevance to anything the universe is doing. Is quantum physics logical? What about a black hole?
Seeing as we already have a mathematical construct that works similarly–the line–I don’t see why it would be a problem. Look at the real number line. Just because there’s an uncountable number of integers before 2 doesn’t mean we can’t add 2 more and get to 4.
And logic has a very specific purpose: to create a consensus reality. And, yes, a black hole and quantum physics are both logical–there couldn’t be math that describes them otherwise, as math is merely a type of logic. I think what you are thinking of is common sense.
You’re missing the point. It’s easy enough to get from 2 to 4. But first you have to get to 2. Think of the integers as seconds, and 0 as the present. How many seconds will need to pass before the present arrives? It will never get to zero, not until an infinite amount of time is done–and it never will be.
But given an infinite past then there is no contradiction involved when you say it took an infinite number of seconds to get to right now. The infinite amount of time you need has already happened.
Assume a chain of sequential universes, extending into the past and future to infinity. If that’s the case then there must always be a universe in existence. It seems paradoxical to say that some universe would exist “now” but our universe could not.
This argument can be made over any interval of time, not just one stretching to negative infinity. Between any two seconds, I can make an infinite number of subdivisions. By your Zeno-esque argument, then, it should take an infinite amount of time for a second to go by. I’m reasonably confident that that is not the case.
Yes, both quantum physics and black holes are “logical”; they are mathematically describable.
I’d say the truth is the eact opposite of what you say; the universe is logical, and logic is something that strongly violates “human intuitions”. After all, why else than your own “human intuitions” do you think that a black hole or quantum physics are “illogical”? True, they are weird…but that’s a human prejudice, not a logical flaw.
To call such an enormity a “logical impossibility” may merely shed light on our concept of “logic possibility.” The universe is not limited by our concept of “logical.”
That’s similar, but not the same argument. There are a number of proposed solutions to Zeno’s paradoxes. But an infinite amount of time is, well, infinite. Unless it’s not, in which case there’s no infinite regress and nothing illogical.
