What physicist–and in particular, cosmologists–know about the origin and nature of the universe is that they actually know a hell of a lot less that most non-physicists think they know about the topic. In fact, it would be an essentially true statement that nobody really knows anything about the “nature” of the universe; we can just describe the behavior of objects within it and the structure of the underlying plenum with increasingly complex and arcane mathematical models, all of which either break down or fail to give sensible answers at extreme levels of energy, time, and distance.
As for the query of the o.p., the only factual answer is that we don’t know, and it is staggeringly likely that we will ever be able to answer those questions with any objective evidence to any degree of certainty. At best, we may be able to make some causal inferences based upon the comparitive values of the fundamental physical constants, the underlying large scale structure of space, and the interactions of forces and how all of the above may have evolved with time, in a manner roughly analogous to how we can determine the shapes of Laurasia, Gondawana, and Pangaea by looking at geological strata and formations.
I never saw the appeal of pointing to causes outside the universe, whether it’s god or membranes colliding. Maybe it’s empirically true, but it just moves the questions up another level. Either something has existed forever, or there was an uncaused cause.
First, spacetime appears quantized; there’s a smallest meaningful quantity of time and space. Which means that there’s no such thing as an infinitely short “moment”.
And second, the favored scientific viewpoint seems to be that the passage of time is only a creation of our limited perspective. That in reality time is an unmoving whole, and in essence everything had already happened when the universe was born.
More time, or rather spacetime. Just because our universe has a beginning doesn’t mean there wasn’t another universe before it, or that it isn’t embedded in a greater universe. Many cosmological theories take exactly that position.
It doesn’t work as an explanation though, because either we’re saying there “just was” nothing, which then “collapsed” into something, or just there always was something, and the point is moot.
Either way, we’re starting with an ontological assertion with no reasoning behind it.
I’m certainly not suggesting a religious explanation.
I am an atheist, and I think it’s clearly the case that religious “answers” just push the question back a level (at best; more often they throw up many more questions).
I’m just simply acknowledging that this fundamental philosophical question is not answered at this time, and perhaps never will be and never could be.
Of course we could say that the answer is that the universe “just is”. But this is a meaningless statement. If I say I don’t know why it rains, and you say the rain “just is”, those statements are neither in agreement nor contradictory. The latter is saying little more than “shut up”.
And that’s just what it is; errant speculation. Such models area fun toy to play with and they sell a lot more books than talking the history of electrodynamics, but they don’t produce any testable hypotheses.
I don’t mean to be harsh; it is just that these speculations require observation at energies and distances that are so vastly beyond even theoretical capabilities, and often conditions we don’t know can exist, that there is just no way to falsify these speculations. They’re interesting as a mental exercise but not applicable in any practicable fashion and very likely completely wrong. But then, so are the vast array of physical theories which have ended up funnelling us toward our current understanding of the mechanics of the universe. Even wrong answers–provided they are definitively wrong–are worthwhile.
What do I mean by linear time:* A series of moments where we move into the future as we move away from the past.*
(Time may not truly (or at a deep level) be set up this way, and a part of my assertion is pointing out that this is a possibility.)
Technically, in this model: all we have is a series of “nows” passing us by. Here’s a now, here’s a now, here’s a now. What I am saying is that an infinite amount of these entities could not have existed, at least not in a way we call infinity. I get that you can CONCEPTUALIZE an infinite line going behind us, but it is a different story to say “I am holding in my hand an infinite amount of integers” or “I HAVE WITNESSED AN INFINITE AMOUNT OF SECONDS BEFORE NOW.” Imagining there was some sort of conscious being in all of the past, that could be said: “I HAVE WATCHED INFINITE HOURS OF TIME BEFORE THIS MOMENT.” It is not possible, for you can’t ever actually reach infinity, not without being beyond this physical universe anyway…
I can’t say I fully understand what is being talked about when people say that “time IS infinity”. Mind going into more detail?
PS: An infinite length of time behind us is able to be sliced up into hours or minutes to where you would be able to say: “I have an infinite amount of time,” “I have an infinite amount of minutes,” or “I have an infinite amount of hours”
This is awesome. This makes sense, although what I am saying makes sense too, so I am going to think about this.
Potentially there was a beginning of time, however instead of a series of infinite moments being there, there was only a limited amount of moments? Maybe our universe within linear time will not be that way forever… maybe we never were in linear time…
One of my favorite treatments of time comes from time-travel science fiction or fantasy books. And time-travel games!
In this view, there are two levels of time. Ordinary dates – A.D. 1066, A.D. 1945 – and subjective time for the time-travellers. “I just went back and assassinated Hitler, but then he went back and assassinated Lopez, so it comes out even. Now I’ve got to go back and assassinate Murray, and then acquire the Koh-i-Noor before he goes back and assassinates Gerlach.”
Wonderfully and massively confusing. Fritz Leiber called this higher dimension of time “The Big Time” in his time-travel novel of that name.
Thanks for sharing. This is a good reminder too, some of my highest thoughts about time came from contemplating the possibilities of how time works through a time traveller on the TV show ‘Heroes’
But again, this isn’t necessarily implied by an infinite past. The question here isn’t just the cardinality, but also the ordinality of the set of moments in time: if we consider time to be of the same ordinality as the integers, then for any given moment anywhere in the past, only a finite amount of time has passed, because there are only finitely many numbers between any given two integers (and all distances between two integers are finite). There’s no ‘beginning at -infinity’, there is simply no beginning. If you’re saying that an infinite amount of time has elapsed since some time ago, then you’re asserting a contradiction: both that the universe is infinite, and that it had a beginning. If it genuinely had no beginning, then the time elapsed since any point in the past you could choose is finite, if unbounded.
It’s different if the set of all moments in time is equal in ordinality to the rational numbers: then, there are two moments between which there are infinitely many, even though there are as many rationals as there are integers. But then, in fact, there are infinitely many moments between any two moments, and thus, the problem arises not only between the infinitely distant past and now, but between any two nows. Things like this are what tripped Zeno up, but in fact, thanks to some more modern mathematical understanding, it’s easy to see that traversing this infinite amount of moments only takes a finite amount of time.
Another quirk here is that even a finite past does not necessarily imply a beginning: a set of rational numbers does not generally have a smallest member, so if you consider the open interval (0;1], there is no number q such that there is no smaller number, since if you presume it’s (say) 1/n, you can always choose 1/(n+1) < 1/n. But then, there is no moment such that there is no prior moment, i.e. there’s no first moment—no beginning.
Of course, our current physical theories all describe time in terms of the continuum of real numbers—which is of a genuinely different cardinality, that is, of which there are more than either the rationals or the integers.
I’m not sure everything you are saying here. I am not a math major. However: You seem to say time is not the same as there being numbers. I disagree. That is how linear time is defined: real moments on a line. You say what I am saying: It’s a contradiction to say an infinite amount of time has gone by in the past.
You say: “But then, in fact, there are infinitely many moments between any two moments” … “it’s easy to see that traversing this infinite amount of moments only takes a finite amount of time.”
This isn’t that you are traversing an infinite amount of moments. In the sense that time is a line, lets imagine “one foot” of time. One foot can (for all we know) be divided over and over to infinity. But that is not what is meant. You can segment an amount of length however many times you want (for all we know), but you still have the original length that you started with. THAT ORIGINAL LENGTH is not an infinite length. (Outside of miracles, and/or extra dimensions or things like that
Yes. But the thing is, in an infinite universe, we haven’t traversed an infinite amount of time to get to ‘now’. Consider the analogy of distance. A temporally infinite universe corresponds to an infinite line. But, the difference between any two points will be finite.
Thus, from now to any point in time, there’s just a finite amount of time in between. Therefore, we haven’t gone through ‘an infinite amount of moments to reach now’, to quote your OP, even though, in this case, time didn’t have a beginning. Just like you don’t have to walk an infinite distance to get to a point on an infinitely long line from any other point on that line. If you think you do have to walk an infinite distance, you’re imagining starting somewhere way out ‘to the left’ on that line, some point at ‘-infinity’. But there just isn’t such a point.
It’s not an “explanation” but more of an analogy. Quantum flunctuations in empty space are a function of quantum uncertainty and supposedly describe how “something” can be created out of “nothing”, but as someone pointed out elsewhere, it’s really more a way of saying that “empty” space has interesting properties and isn’t as “empty” as we thought. But the Big Bang didn’t occur in space, it created space – and time.
Hawking endorsed this under his Euclidian space-time hypothesis, which says that true time is a Euclidian property of space-time just like the spatial dimensions, and the peculiar view of time as an inexorable flow is an illusion of our perception. In this view, the Big Bang isn’t a singularity at all, but just an ordinary coordinate in a finite but unbounded universe. It would be no more mystical or God-like than the North Pole, from which all the lines of longitude emerge.
One more thing. Since we know energy and matter had a beginning, in our universe at least, when you speak of infinite negative time you are making an assumption that time and energy/matter are independent. We know from relativity that this is not totally true. If there is no time before the beginning of energy/matter, there is no infinite moment paradox.
Conceiving of no time is probably impossible for us, but that doesn’t mean it isn’t correct. We don’t understand time very well, after all.
Why are you saying we are living in an infinite universe, if that’s what you are saying?
I still disagree with your point. I can’t follow it all perfectly, but it still seems to go against the idea that there to be a beginning of time, or an infinite past (which is an impossibility, within our current understanding)
I don’t see how you can claim that there can be an infinite past while we have gotten to here at this point. Hypothetically, someone who has watched all of the past could not have gotten to now because someone cannot view an infinite length of time. This is another way of saying that someone cannot have watched a succession of an infinite amount of events. Implying an infinite past implies that all of the past could have been watched by an observer, which is a self-contradiction (outside of other-dimensional phenomenon or miracle ability, etc.)
I (somewhat) agree with what you are saying. On one level, what time is is a man-made measurements to describe a length of moments (a second, minute, hour, or year is all described by us to define a length of events). My argument still holds water (that I can see) if you look at this as a problem of an* infinite past* problem, not an infinite time problem.
By the way, the idea that energy/matter came from non-energy/matter is another huge thing: It is another paradoxical statement to assert that matter/energy exploded from nothing. (You are not specifically saying this, but this is one idea floating around out there which by definition as far as we know cannot be)
How can time arise from a timeless realm? There seems to be no order of events which would eventually give rise to the realm of time, unless it was within the timeless realm at the start somehow…