Infinite time?

[caharris]

I was discussing the details of what it meant to say that time was infinite, specifically into the past.

 

The main objection that I got was that "if the past is infinite, then it would have taken an infinite of time to reach the present." My first impulse is to say "So?" and ignore it, but I was having difficulty explaining why that didn't bother me.

 

So I'm curious as to what you guys think. Could time extend infinitely into the past? If so, what would that mean? If not, why?

Edited January 10, 2011 by caharris

[cypress]

I didn't vote for either of the three. While it may be possible that time past or time future can be eternal (never ending) I don't think it is correct to describe it as infinite. As far as I know, there are no examples of any actualized infinite physical anythings and until evidence surfaces that there are real physical infinite entities one should resist such speculation.

[ydoaPs]

I vote false trichotomy.

[caharris]

I didn't vote for either of the three. While it may be possible that time past or time future can be eternal (never ending) I don't think it is correct to describe it as infinite. As far as I know, there are no examples of any actualized infinite physical anythings and until evidence surfaces that there are real physical infinite entities one should resist such speculation.

There are no examples of actual infinities? Divide the distance between one centimeter to another centimeter over and over again. Wouldn't you be able to do this for infinity?

 

I vote false trichotomy.

If you have another option that you think I should add let me know.

[ydoaPs]

What about "Yes. Infinite past with finite future." or "Undecided. The available evidence is inconclusive." or "Other. Explain in a post below."?

[caharris]

What about "Yes. Infinite past with finite future." or "Undecided. The available evidence is inconclusive." or "Other. Explain in a post below."?

Added. Thanks for the suggestions.

[Mr Skeptic]

My guess is that time is some kind of infinite, however I don't think anyone actually knows and there are more possibilities than you seem to think possible. For example, our universe might be finite in time and this would probably imply a finite time dimension for our universe. Although we don't know what came before our universe it seems reasonable to speculate some sort of order to events, and so a time dimension of sorts separate from our own. Our universe could be cyclic, in which case our own time dimension might be infinite. Closed time loops might be possible but I don't know whether that would even be considered infinite or not.

[cypress]

There are no examples of actual infinities? Divide the distance between one centimeter to another centimeter over and over again. Wouldn't you be able to do this for infinity?

 

 

If you have another option that you think I should add let me know.

 

I voted other now. The reason is as I explained above. Thanks for adding that. Mathematical constructs like your examples above are not physical actualities. Math models reality but it is but a model. In the physical world one cannot divide the distance an infinite number of times due to numerous limitations that come into play. do you see the distinction I am making?

[caharris]

I voted other now. The reason is as I explained above. Thanks for adding that. Mathematical constructs like your examples above are not physical actualities. Math models reality but it is but a model. In the physical world one cannot divide the distance an infinite number of times due to numerous limitations that come into play. do you see the distinction I am making?

While I agree that there are limitations, the distances of 1/2, 1/4, 1/8, 1/16... are still crossed regardless of whether we can measure them in practice. If I move my hand a specific distance, I still cross every infinite fraction even though I couldn't get out a ruler and measure it.

[cypress]

While I agree that there are limitations, the distances of 1/2, 1/4, 1/8, 1/16... are still crossed regardless of whether we can measure them in practice.

 

Yes, but surely you recognize that each of those distances that were crossed were finite and every non zero distances moved were finite. In the real world thus far everything seems to be finite.

 

If I move my hand a specific distance, I still cross every infinite fraction even though I couldn't get out a ruler and measure it.

 

It is clear that if you move your hand each real distance traversed is finite. What is not clear is whether or not any physical distance is infinitely small or if there exist an infinite number of these distances in actuality. How could you demonstrate that there are? If there are an infinite number of distances between one centimeter and another then there are a larger number of infinite distances in two centimeters. How do you reconcile this?

[Mr Skeptic]

While I agree that there are limitations, the distances of 1/2, 1/4, 1/8, 1/16... are still crossed regardless of whether we can measure them in practice. If I move my hand a specific distance, I still cross every infinite fraction even though I couldn't get out a ruler and measure it.

 

But can you prove that each of these points is different from each other? Maybe points 1/8 and 1/16 are in fact the same point, we just don't know that space is in fact infinitely divisible like the real and rational number lines.

[caharris]

Yes, but surely you recognize that each of those distances that were crossed were finite and every non zero distances moved were finite. In the real world thus far everything seems to be finite.

Well yeah, but isn't 'infinity' made of a bunch of finite things? Infinity may be a never ending number, but it still has the finite number 'one' in it...

 

It is clear that if you move your hand each real distance traversed is finite. What is not clear is whether or not any physical distance is infinitely small or if there exist an infinite number of these distances in actuality. How could you demonstrate that there are? If there are an infinite number of distances between one centimeter and another then there are a larger number of infinite distances in two centimeters. How do you reconcile this?

It would be finite because you would be dividing up that distance into fractions, not adding distance to the total displacement of my hand. I'm not trying to defend, what's it called, Zeno's paradox? Where a runner travels half the distance of a field, then half again, then half of that... What I'm saying is that all of those distances are a part of the total finite distance.

But again, I could only prove this in principle, not practice. I think it is reasonable to say that since we can divide a centimeter into a millimeter, we could continue to divide that centimeter up into smaller and smaller segments.

How would I reconcile the addition of another centimeter? Well, wouldn't the answer just be that there is an infinite number of infinitely small distances in between the two centimeters?

 

But can you prove that each of these points is different from each other? Maybe points 1/8 and 1/16 are in fact the same point, we just don't know that space is in fact infinitely divisible like the real and rational number lines.

I would think you couldn't, simply because you wouldn't keep the original point (in this case 1/8), but you would break up the original centimeter into 1/16. Eventually, you would just get an infinite number of infinitely small distances.

 

(I've just started getting into the math of infinity, so forgive me if I'm making an error. I'm not trying to argue with you, I'm just trying to understand.)

Edited January 10, 2011 by caharris

[Mr Skeptic]

OK, consider traveling along the integer line from point 0 to point 4. Fractions are not part of this number line, so 1/2 the distance is at point 2, 1/4 the distance is point 1, 1/8 the distance is .5 which is not on the number line but gets rounded to 1, and any smaller fractions are all rounded down to point 0. There's only 5 points including the start and end points. And we don't know whether reality is like the real number line or like the integer number line -- it might or might not be infinitely divisible.

 

For example, try infinitely dividing a cake and see what happens.

[TonyMcC]

I voted "No". I have heard it said that time itself started for this universe at the "big bang". By the same argument I suppose time will end for this universe when the universe comes to the end of its existence. Perhaps this will happen if the expansion is cyclic and everything goes over a maximum and then eventually shrinks back to nothing.

Edited January 10, 2011 by TonyMcC

[michel123456]

other.

explain below (without entering Zeno's paradox):

I think time is relative. IMHO Time has a beginning for any observator and has an end for any observator. Both ends are horizons.

The word "observator" may drive into misunderstanding. "Observator" does not mean "Human Being" or "Intelligent Being", observator here mean "a participant of the Universe", i.e. any body, any particle.

[caharris]

OK, consider traveling along the integer line from point 0 to point 4. Fractions are not part of this number line, so 1/2 the distance is at point 2, 1/4 the distance is point 1, 1/8 the distance is .5 which is not on the number line but gets rounded to 1, and any smaller fractions are all rounded down to point 0. There's only 5 points including the start and end points. And we don't know whether reality is like the real number line or like the integer number line -- it might or might not be infinitely divisible.

 

For example, try infinitely dividing a cake and see what happens.

That's why I wanted to make the distinction between in practice and in principle.

You voted that time is infinite in the past and future. If this is the case, then aren't you disagreeing with the principle of your own objections? (Not calling you out, just trying to understand.)

 

 

other.

explain below (without entering Zeno's paradox):

I think time is relative. IMHO Time has a beginning for any observator and has an end for any observator. Both ends are horizons.

The word "observator" may drive into misunderstanding. "Observator" does not mean "Human Being" or "Intelligent Being", observator here mean "a participant of the Universe", i.e. any body, any particle.

Do you think that something like a quantum field could have existed for infinite time?

[Mr Skeptic]

The integer number line is infinite despite not being continuous. The real number interval between 0 and 1 is continuous but finite, yet it has uncountably infinite numbers on it. These are two separate things.

[Anura]

If time is infinite. It took an infinite time to reach this point. Redefining infinite. Or am i confused?

[caharris]

If time is infinite. It took an infinite time to reach this point. Redefining infinite. Or am i confused?

To be honest, I have no idea. That's why I asked

[1123581321]

I don't believe time as we know it and experience it exists at all. I believe there is no such thing outside of consciousness and that everything may well exist as it does within the confines of the atom. I also believe that time travel is within the bounds of consciousness and not time.

[caharris]

Red pill or blue pill? (Matrix reference. Couldn't help myself.)

[escape_velocity]

Mr. Skeptic said: Our universe could be cyclic, in which case our own time dimension might be infinite. Closed time loops might be possible but I don't know whether that would even be considered infinite or not."

 

Coincidentally, I used the phrase "time loop" some weeks ago at some other website in a comment elicited by this question: " (...) is every universe always the same as the one that came before it? (Is it like rewinding the same tape over and over (...)?"

 

My comment:

 

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That's exactly what the Stoics believed.

 

See, for example, Nemesius, "De nat. hom.", 38: "When the heavenly bodies, in the course of their movement, have returned to the same sign and to the latitude and longitude that each one occupied in the beginning, there takes place, in the cycle of the times, an utter conflagration and destruction; then there is a going back, from the start, to the same cosmic order and once again, as the heavenly bodies move just as before, every event in the preceding cycle repeats itself without any difference whatsoever. In fact, Socrates and Plato will exist again, and every individual with the same friends and fellow citizens, the same beliefs and the same arguments in discussions, every city and village, will come back. This universal return will happen, not just once, but many times, to infinity."

 

In our days some would call this a "time loop", and they'd say we're trapped in one.

 

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...and as for Zeno's Paradox, mentioned by "michel123456", it's only apparent. His reasoning was that, since one can divide any distance into an infinite number of segments, movement is impossible because anything would have to spend an infinite amount of time traveling over all those numberless segments. His mistake was confusing the physical realm with the mental realm. In the latter the mind can divide a distance an infinite amount of times, but in the former space is not divided but is continuous, so that movement implies no impossibility whatsoever.

Edited January 21, 2011 by escape_velocity