Time, as a philosophical concept, deals with thought (or the measure of how far back we can remember things). In a universe full of things, we perceive changes, and through them, time. For all we know, things have changed, have been changing and will change regardless of ourselves, which makes it necessary for there to be a before and an after. But this doesn’t correspond to the universe, since the cosmos is indifferent towards change. In it, just energy states prevail. So much so, that time as we know it only came about when we started to record these progressions of states.
Yet, our brains then loop this sensory information and, given that we assume said input is from “right now”, any other information we receive is interpreted as being “old”. And once we realise certain patterns, we are able to picture sensory data we didn’t have but probably would at some point; thus, inventing the future. So, as a mental construct, we’ve got no reason to suppose the past and future don’t continue forever.
However, there’s a limit to these constructions. The past can only go as far as we can remember and the future can only arise as far as we can imagine. Both concepts become increasingly meaningless the backwards you remember and the further you imagine. Hence, our mental pasts and futures have a limit, and it is in their limits that we find ourselves thinking of time as something finite.
But, is time really finite because we think it so?
That might be a bit too much solipsism for my liking, so why don’t we consider a bigger scale? Say, the universal scale, where we must go to the very beginning of things. And by beginning I mean, of course, the Big Bang.
Now, the really cool thing about this bang, besides being big, is that through it an important thing happened: the known universe. How or why is still a matter of speculation, so we’ll leave that out for the time being. What matters to us is the way in which this initial cause evolved into the effects we see today. Particularly in regards to the geometry of our universe, where we’re allowed some ground for speculation. And speculate we have and three possible scenarios our minds have come up with. These being:
- negative, and
Which are just proper ways of explaining universal curvature. But curves don’t matter much to our present narrative unless we acknowledge their implications, so let’s see what each setting means for the universe.
Scenario #1: Positive Curvature
If the curvature of space is positive, there would be more than enough mass to cause the expansion of the universe to stop. The universe would then have no ends, but its expansion would eventually stop and turn into a contraction, which would force the universe to collapse on itself. Therefore, we’d be dealing with a closed universe, an elliptical (sphere-like) space and finite time.
Scenario #2: Negative Curvature
If the curvature of space is negative, there would be insufficient mass to cause the expansion of the universe to stop. The universe would then have no bounds and expand forever. Therefore, we’d be dealing with an open universe, a hyperbolic (saddle-like) space and infinite time.
Scenario #3: Zero Curvature
If the curvature of space is zero, there would be exactly enough mass to cause the expansion of the universe to stop, but only after an infinite amount of time. The universe would then have no bounds and expand forever, but the rate of its expansion would gradually approach zero after an infinite amount of time. Therefore, we’d be dealing with a flat universe, an euclidean (sheet-like) space and potentially infinite time.
Having established the background, we may then ask: What kind of curvature fits our universe? Until now, we have many reasons to believe that the known universe is flat; which would mean that time, under physics, should be thought of as a potentially infinite magnitude.
But if you’re observant enough, you probably noticed something a bit sketchy about that “potentially” and here’s what:
If the universe keeps expanding forever, its entropy will just keep increasing. Meaning that stars will burn out, planets will collide or spiral out into empty space, and all life will die. Gradually, every point in the universe will slowly get more isolated from its closest neighbours until it all goes about floating as an unchanging island in an infinite sea of nothingness.
So will there be a passage of time in the universe once it reaches this theorised state? We could make arguments for both sides, but the truth is: we don’t and can’t know.
Fortunately for us, we’re here, experiencing the best of all the time we’ll ever get to know. And that’s more than enough reason to go without answers for now and the days to come.