"Time can't be infinite because.."

1MileCrash

One of my closest friends have frequent discussions about science and math.

He has said to me on a couple of occasions:

Time cannot be infinite because if it were then this moment could have never came, because an infinite amount of time came before it.

I don't like this reasoning. Is my gut correct or is there some truth to what he is saying? I can't put it into words but, this isn't right..

zhermes

No truth or backing whatsoever. That makes no sense at all.

It is very similar to one of Zeno's paradoxes: The dichotomy paradox---in which you can never reach a destination without first going half way, and there are an infinite number of half-ways between you and your destination... thus it might seem you can never reach the destination.

This is similar to (but not quite equivalent) to there simply being an infinite number of points between any two locations in space (or time for that matter); but that doesn't keep you from traversing that distance (or time).

Calculus can easily dispense with these issues.

rcgldr

Unlike Zeno's paradox which decribes finite duration and finite distance events with descriptions that include limits of infinite term expressions, this is a case where someone is asking if time is infinite.

One argument against time going back infinitly is related to entropy, such as temperatures within any system evening out over time. You'd also have the issue of heat and light energy lost due to infrared waves escaping the physical part of the universe composed of matter. Still this is based on a theory that assumes that there can't be some cyclical nature to the universe.

Another argument is for anything (like the universe) that exists here and now, no matter how far it travels in distance or time, it will end up at some finite amount of distance or time from where it is now.

zhermes

No; this is a case where someone is asking about a particular argument against time being infinite.

Again, while an interesting topic, this isn't quite the point.


The issue is completely untestable and unanswerable (at least at present). There are theories which agree with what you're saying, and others that completely dismiss them or explain them away.

rcgldr

To extend that particular argument, if a infinite amount of time came before the present, then any non-cyclical aspects of the universe would have taken place by "now".

Another related argument could the the probability of existance during any finite period of time. As the limit of time goes to infinity, the probability of existance at any specific finite period of time goes to zero. Where's the origin for anything that is infinite?

I agree that these arguments are based on theories about the nature of the universe.

1MileCrash

Actually, that is a topic he has a firm misunderstanding of. He is very, very smart, much moreso than me but in these topics I'm not sure he's done any reading.

He basically, agrees with zeno's paradox. "If I were to travel halfway to the refrigerator, then half again, then half again, then half again, I would never reach the refrigerator." And that repeatedly halving the distance is a different situation than just plainly walking to the refrigerator.

I walk to the refrigerator and reach it, to display the incorrectness.

Yet, that is two different situations according to him. He seems to think there is a difference between "actually" walking half way, then half way again, then half way again, and just walking to the refrigerator.

Just because I am smoothly walking towards the refrigerator at a constant speed doesn't mean I'm not repeatedly halving the distance traveled.

I'm guessing it just boils down to a fundamental disagreement.

36grit

The Universe is a sea of time.
Every universe has a begining and an end, But do not worry, their children will endure until the appointed time of rest.

Then it's back to work again :)

rcgldr

If velocity is constant, and the toal time to reach the refrigature is "t", then you spend time t/2 walking the first half, then t/4 for half again, then t/8 for half again ...

The total time = t/2 + t/4 + t/8 + t/16 ... + t/∞ = t

So the total time for constant velocity remains the same no matter how you divide the time up. It's still a finite amount of time.

The original question was about time being infinite, which could be rephrased to ask if the universe had a beginning or was it always here?

deigm

I think your friends argument actually supports infinite time. Because it only works if there is a destination (a finite amount of time). You cant halve infinity. And using the assumption that there is a destination to prove there is a destination is circular logic.
Tell your friend there is no fridge. hehe :)
I dunno correct me if im wrong im just thinking..

36grit

I've recently come to the conclusion that infinite fields require infinite expansion. The universe is sea of time, and time is an infinite field. But in a "static instant" of time, the universe is finite.

soothsayer

Your friend it probably right in a practical sense. If the Big Bang model of the universe is correct (which is appears to be) then our own universe can't be infinitely old, at least not in the way we define time by that model, that time begins with the rest of the universe at the Big Bang. That is, as we let time go to zero with the Big Bang and General Relativistic equations, the universe becomes infinitely hot and dense, and we cannot mathematically or logically wind the clock back any further.

That doesn't necessarily mean he's right in a general/philosophical sense. Old cosmological models like the Big Bounce and Steady State relied on the fact that the Universe must be infinitely old. Is that even possible? Who knows. Your friend's assertion is that if we are here, then a infinite amount of time must have passed to get to this moment. Basically, if time began an infinitely long time ago, we would never have gotten to this moment, or any moment in time. I think this argument goes beyond properties that he or anyone else could reasonably know about time. It almost feels like a straw man argument to me. Time as a measuring system is really more of a social construct than anything else, so to take this construct and confine it to certain limitations and declare something about the inherent nature of it due to those limitations is just that: Creating an idea, making stuff up about it, and basically inferring some sort of physical implication from nothing.

You could argue there is also time as a dimension, a type of geometry, woven in with the fabric of space, creating the space-time continuum. In this sense, to say time is "infinite" is a poorly defined idea, in my mind.

LostConjugate

Time is only a standard to help measure the rate at which different objects move through space. Is it even logical to speak of the time of time?

SteveL27

I assume you believe in the integers, the numbers ..., -4, -3, -2, -1, 0, 1, 2, 3, ...

They have no beginning and no end; but any time you need an integer, say 47, you can just use it. You don't need to go through all of them left to right.

Time is like that. We're here now. We know that for certain. How we got here is for the philosophers and theologians.

Hmmmmmm ... perhaps time is like a tape that's infinite in both directions with but with random access if you have a high enough permissions. So if you have your "God bit" set, you can get to any instant you need ... instantly.

Just sort of kidding with that last remark ... but the integers give a very nice model of a system that's unbounded in two directions, which we can label "past and future," or "left and right" -- they're only labels, after all -- yet any element we need is immediately available to us.

Hurkyl

I just wanted to point out that in the process of

• Walking half-way to the refrigerator
• Walking half of what remains of the distance to the refrigerator
• Walking half of what remains of the distance to the refrigerator
• Walking half of what remains of the distance to the refrigerator
• ...

you do indeed never reach the refrigerator.

The fallacy is in the added assumption that this process is somehow "complete" and that nothing can come afterwards. I can imagine a few odd viewpoints that would justify this assumption -- but that just means those viewpoints are very limited, and incapable of actually undertaking an analysis like the above. (or that the viewpoints are flat-out inconsistent)

PhanthomJay

There is a big difference between walking toward the refrigerator at constant speed, versus walking in halved steps at a constant time per half step. If a refreigerator is 10 m away, and I walk toward it at 1 m/s, I arrive there in 10 seconds. If, instead, I walk the first 5 meters in 1 second, the next 2.5 m in 1 second, the next 1.25 m in 1 second, and so on, then mathematically, I will never get there in a finite time. Physically, after a certain amount of time has passed, I will arrive, assuming I am a point particle, to within a planck's length of the fridge. Then I make my quantum jump across whatever secrets lie within that mysterious space.

agentredlum

Yes, but you are also halving the time it takes to travel the next distance. So according to Zeno philosophy, not only are you stuck in SPACE, but you are also stuck in TIME because the time interval during a jump goes to zero. I don't know if he mentioned time with this particular paradox. he did in others. Ask your friend if he thinks EXISTENCE is continuous. Lets take movement from Point A to Point B. Suppose existence is NOT continuous but consists of 'jumps' in space and through time on the order of the PLANCK LENGTH(google it) and PLANCK TIME. Then it is possible to get from point A to point B because there is a finite number of jumps, even though there is an infinite number of ABSTRACT points between A and B. Same argument for time. It's possible to get from time A(before) to time B(after) because there is a finite number of time jumps, even though there is an infinite number of ABSTRACT time intervals between time A and time B.

Think about watching a film of someone walking. Film is usually 32 frames per second, there are gaps between frames yet when observing the film movement seems continuous. Is movement an illusion? Is physical reality an illusion? If you ask these type of questions then you have caught the 'spirit' of Zeno's phylosophy.

Numbers are infinite but don't forget they are all NEGATIVE left of zero. Ask your friend, what is NEGATIVE TIME? Get him to admit that time had a beginning at zero, then use PLANCK TIME to get to NOW. Time can still be infinite and even using PLANCK TIME it is impossible to get to THE END but NOW should be no problem. This way you both win...for now.

agentredlum

LOL you posted about PLANCK LENGTH while i was writing about it. What is the Quantum Mechanical probability of that? LOL GIVE ME A NUMBER LOL