Infinite time?

[charris]

It seems to me possible that there is an infinite time, specifically that of the past. All that would be required is for a previous event or cause (depending on you interpretation of QM).

I mentioned this, and was met with the objection, "If the past was infinite, then it would have taken an infinite amount of time to get here." I personally think this objection is pointless, so maybe if you think this is the case you could expound upon it. If you disagree, then if you could post your reasons as well I would appreciate it.

Also, if you disagree because of other reasons, I would like to hear them.

[KennethM]

I was thinking about this argument in the context that it is so often made by creationists the other day and realized where I had heard it before. It is really just a rehashing of Aristotle's dichotomy paradox.

"That which is moving must arrive at the half-way point before it arrives at the goal."
—Aristotle, Physics VI

However, every halfway point is, in itself, a goal. When traveling from point A to point B one must first pass halfway point 1, but to get there one must pass halfway point 2 (halfway between A and halfway point 1) and before getting there one must pass halfway point 3... etc ad infinitum. This means that motion is both meaningless and impossible as there are an infinite number of halfway points that one must pass to get to any single halfway point.

[Grumpy]

KennethM

I was thinking about this argument in the context that it is so often made by creationists the other day and realized where I had heard it before. It is really just a rehashing of Aristotle's dichotomy paradox.

"That which is moving must arrive at the half-way point before it arrives at the goal."
—Aristotle, Physics VI

However, every halfway point is, in itself, a goal. When traveling from point A to point B one must first pass halfway point 1, but to get there one must pass halfway point 2 (halfway between A and halfway point 1) and before getting there one must pass halfway point 3... etc ad infinitum. This means that motion is both meaningless and impossible as there are an infinite number of halfway points that one must pass to get to any single halfway point.

And yet it moves. See what logic uninformed by reality gets you?

Grumpy

[KennethM]

KennethM

I was thinking about this argument in the context that it is so often made by creationists the other day and realized where I had heard it before. It is really just a rehashing of Aristotle's dichotomy paradox.

"That which is moving must arrive at the half-way point before it arrives at the goal."
—Aristotle, Physics VI

However, every halfway point is, in itself, a goal. When traveling from point A to point B one must first pass halfway point 1, but to get there one must pass halfway point 2 (halfway between A and halfway point 1) and before getting there one must pass halfway point 3... etc ad infinitum. This means that motion is both meaningless and impossible as there are an infinite number of halfway points that one must pass to get to any single halfway point.

And yet it moves. See what logic uninformed by reality gets you?

Grumpy

Precisely! Seeing as we can move the concept collapses under its own weight, regardless of its logical merits.

[Zeeby]

KennethM

I was thinking about this argument in the context that it is so often made by creationists the other day and realized where I had heard it before. It is really just a rehashing of Aristotle's dichotomy paradox.

"That which is moving must arrive at the half-way point before it arrives at the goal."
—Aristotle, Physics VI

However, every halfway point is, in itself, a goal. When traveling from point A to point B one must first pass halfway point 1, but to get there one must pass halfway point 2 (halfway between A and halfway point 1) and before getting there one must pass halfway point 3... etc ad infinitum. This means that motion is both meaningless and impossible as there are an infinite number of halfway points that one must pass to get to any single halfway point.

And yet it moves. See what logic uninformed by reality gets you?

Grumpy

Actually it's just bad logic. The statement is "if an object passes through infinitely many points with distance between them, it would take infinitely long" which is derived from the (wrong) statement "the sum of infinitely many numbers is infinite".

[fredonly]

It seems to me possible that there is an infinite time, specifically that of the past. All that would be required is for a previous event or cause (depending on you interpretation of QM).

I mentioned this, and was met with the objection, "If the past was infinite, then it would have taken an infinite amount of time to get here." I personally think this objection is pointless, so maybe if you think this is the case you could expound upon it. If you disagree, then if you could post your reasons as well I would appreciate it.

I agree with the objection you stated: that if the path were infinite, we couldn't have arrived at today. I'll give you the argument.

The past and the future are different. The past is completed, it is over and done with. The future is just a potential. The past is immutable; we can't change it. But we CAN affect the future through our actions.

The future extends indefinitely, into the future - but this is just a potential. Taking time one day at a time, you will never reach infinity. An infinite future implies just that at any time there are always more days ahead.

But there's no coherent way to describe an infinite past, because to arrive at today would require an infinite number of past days to have been completed. This would be an actual infinity, as opposed to the future, which is merely a potential infinity. The past has no potential since the past is completed (one more day gets added to the past each day, but at any instant of time the past is fixed and without potential). For an infinite number of days to have passed, it implies we have reached today by counting from an actual negative infinity to today. But you can't count to infinity, and you can't count from -infinity to 0.

This argument is counter-intuitive to anyone who is familiar with a number line, extending from -infinity to +infinity. But the key is to grasp the asymmetry of time, the past being completed, and the future being just a potential. Actual infinities do not exist in the real world; only potential infinities.

I was surprised to see that so many voted that neither the past nor future is infinite. Can someone of this persuasion explain why they don't believe the future is potentially infinite?

[McCulloch]

I don't think that the concept of spacetime allows for one dimension (time) to be finite in one direction and infinite in the other. Thus, if relativity is correct, time must be infinite past and future or finite past and future.

Past and future are only abstractions. Past is the time before an arbitrary point we call now. Future is the time after now. How does anyone know that they can change the future? Do you know that you could have done anything other than what you have done?

[fredonly]

I don't think that the concept of spacetime allows for one dimension (time) to be finite in one direction and infinite in the other. Thus, if relativity is correct, time must be infinite past and future or finite past and future.

Just because the mathematics of relativity are not bounded in the past or the future doesn't imply reality is necessarily unbounded as well.

Past and future are only abstractions. Past is the time before an arbitrary point we call now. Future is the time after now. How does anyone know that they can change the future? Do you know that you could have done anything other than what you have done?

I see no justification for this assumption, and suspect you may be reading too much into the way time is represented in a graph or on a number line. The past is fundamentally different from the future. Yesterday no longer exists, but it typically leaves a trail (such as our memory). Tomorrow doesn't exist (not now).

I'll grant that General Relativity treats time in the way you suggest, but again - this is just a mathematical representation. At most, it implies that some computations can be successfully made by representing time in this way; it doesn't imply that time really is that way.

[Grumpy]

McCulloch

I don't think that the concept of spacetime allows for one dimension (time) to be finite in one direction and infinite in the other. Thus, if relativity is correct, time must be infinite past and future or finite past and future

Relativity is correct, but it is not a complete picture or description. Mathematically time should be able to flow in either direction, but we know that is not an accurate description. All timelines had a beginning(as this Universe experiences time, anyway), most will probably have endings(by entering a Black Hole), some will not and will continue to exist indefinitely(though it will always be a finite time from it's beginning.

Is that infinite? Depends on your definition of "infinite", I guess.

Grumpy

[charris]

I agree with the objection you stated: that if the path were infinite, we couldn't have arrived at today. I'll give you the argument.

The past and the future are different. The past is completed, it is over and done with. The future is just a potential. The past is immutable; we can't change it. But we CAN affect the future through our actions.

The future extends indefinitely, into the future - but this is just a potential. Taking time one day at a time, you will never reach infinity. An infinite future implies just that at any time there are always more days ahead.

But there's no coherent way to describe an infinite past, because to arrive at today would require an infinite number of past days to have been completed. This would be an actual infinity, as opposed to the future, which is merely a potential infinity. The past has no potential since the past is completed (one more day gets added to the past each day, but at any instant of time the past is fixed and without potential). For an infinite number of days to have passed, it implies we have reached today by counting from an actual negative infinity to today. But you can't count to infinity, and you can't count from -infinity to 0.

This argument is counter-intuitive to anyone who is familiar with a number line, extending from -infinity to +infinity. But the key is to grasp the asymmetry of time, the past being completed, and the future being just a potential. Actual infinities do not exist in the real world; only potential infinities.

I was surprised to see that so many voted that neither the past nor future is infinite. Can someone of this persuasion explain why they don't believe the future is potentially infinite?

This is the same thing that William Lane Craig says, and it drives me absolutely insane: potential infinities. If models of the world mean anything, then the distinction between 'potential' infinities and 'actual' infinities is absolutely pointless. The fact of the matter is, we use models to describe the real world, and the models give us infinities.

Of course you'll never reach infinity. To suggest otherwise is quite odd. Yet, you do just that. To say that "to arrive at today would require an infinite number of past days to have been completed," no. An infinite past number of days since when? An infinite past means we never started counting, we just always have been. And how can you have an infinite future without an infinite past? The ability to change it is irrelevant.

I gave the example of a person walking. If a person has always been walking, he still makes progress forward. There is nothing stopping you from walking up to him. And no matter what, he's walked a distance. Saying that he can't progress because he's always been walking is mind boggling. Time still moves, just as the person still walks forward. Not being able to reach a point where he started walking is pointless (pun intended).

Time is symmetric, by the way.

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I was browsing the web for similar conversations, and I came across this. On post 35 and 37, it is shown using math that you can traverse infinities.

[fredonly]

I agree with the objection you stated: that if the path were infinite, we couldn't have arrived at today. I'll give you the argument.

The past and the future are different. The past is completed, it is over and done with. The future is just a potential. The past is immutable; we can't change it. But we CAN affect the future through our actions.

The future extends indefinitely, into the future - but this is just a potential. Taking time one day at a time, you will never reach infinity. An infinite future implies just that at any time there are always more days ahead.

But there's no coherent way to describe an infinite past, because to arrive at today would require an infinite number of past days to have been completed. This would be an actual infinity, as opposed to the future, which is merely a potential infinity. The past has no potential since the past is completed (one more day gets added to the past each day, but at any instant of time the past is fixed and without potential). For an infinite number of days to have passed, it implies we have reached today by counting from an actual negative infinity to today. But you can't count to infinity, and you can't count from -infinity to 0.

This argument is counter-intuitive to anyone who is familiar with a number line, extending from -infinity to +infinity. But the key is to grasp the asymmetry of time, the past being completed, and the future being just a potential. Actual infinities do not exist in the real world; only potential infinities.

I was surprised to see that so many voted that neither the past nor future is infinite. Can someone of this persuasion explain why they don't believe the future is potentially infinite?

This is the same thing that William Lane Craig says, and it drives me absolutely insane: potential infinities. If models of the world mean anything, then the distinction between 'potential' infinities and 'actual' infinities is absolutely pointless. The fact of the matter is, we use models to describe the real world, and the models give us infinities.

First and foremost, models should not be confused with the actual real world. Infinity is useful in mathematics. I can derive the volume of a sphere by calculating triple integrals, using calculus to add together the volumes of an infinite number of infinitesmal cubes. But it's just an abstraction, one with interesting and useful properties - but an abstraction none the less. But try actually chopping up a sphere into an infinite number of infinitesmal cubes. You can't. It's not real world. The question about time is real world. Just because you can conceptualize time extending infinitely in both directions does not make it so. And incidentally, Craig didn't invent the idea of potential infinity. Aristotle dealt with it. Finally, it’s not pointless at all – it’s at the heart of the very real arrow of time .

Of course you'll never reach infinity. To suggest otherwise is quite odd. Yet, you do just that. To say that "to arrive at today would require an infinite number of past days to have been completed," no. An infinite past number of days since when?

Any “when� implies a specific point in past time, and it happened a finite number of days ago. You’re basically trying to give the argument that we can just keep right on counting into the infinite past. Yep, you could certainly do that if the past were infinite, but you must first assume the past is infinite in order to start this endless counting. This doesn't make a case for it actually BEING infinite. You're confusing your ability to conceptualize an infinity with it actually existing in reality. A conceptual observation like this certainly does not in any way refute my statement. How can an infinite past NOT entail an infinite number of past days? Clearly, it does.

An infinite past means we never started counting, we just always have been.

Your statement assumes an infinite past, it doesn’t prove there can be one and doesn’t refute my statement that there would have to be an infinite number of past days.

And how can you have an infinite future without an infinite past? The ability to change it is irrelevant.

Here’s how: big bang happens, time begins. Going forward, we see the days proceeding one after another and no reason for this to stop; ie the future is potentially infinite.

I gave the example of a person walking. If a person has always been walking, he still makes progress forward. There is nothing stopping you from walking up to him. And no matter what, he's walked a distance. Saying that he can't progress because he's always been walking is mind boggling. Time still moves, just as the person still walks forward. Not being able to reach a point where he started walking is pointless (pun intended).

Again, you are presupposing an infinite past when you say, “if a person has always been walking…� How can that be?

Time is symmetric, by the way.

How about supporting this assertion. Here’s my support for it being asymmetric:
The past is completed, the future is not completed
The past is immutable, the future is not
Time proceeds in one direction only; there is an arrow of time

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I was browsing the web for similar conversations, and I came across this. On post 35 and 37, it is shown using math that you can traverse infinities.

You’re being fooled by the math. He defined x(t) to be a function that computes the spatial position at time t. He then integrates this position function over an infinite time span, and calculates a finite number. This implies that over an infinite period of time (that is what he is integrating over), it is possible to traverse a finite distance. That certainly doesn’t demonstrate anything relevant. Integration is a mathematical technique for simultaneously adding together infinitesmals. In this case, it’s infinitesimal distances that are being added together, and they are added together simultaneously. Math is great for being able to do this. However, it’s not a real world transversal of time because in the real world, time intervals (no matter how small) occur one after the other, not simultaneously.