# Is time infinite?

by disregardthat
Tags: infinite, time
 Sci Advisor P: 1,797 I have heard the argument that time must have a beginning (I know that discussion about time tends to become vague, because we have no definite definition of time, and that terms can overlap, (especially when talking about infinity) but I hope I make myself clear): "Assume time has no beginning, but that it has existed for an infinitely long time back. Then it would have taken an infinite amount of time until this moment. As an infinite amount of time will never end, this moment could never have occurred, and hence time cannot be infinite - it must have a beginning." (This is not quoted from anywhere) I believe this argument is flawed, because there exist no point on the time line such that there is a period of infinite length between that and this moment. Hence the second sentence of the argument uses a period of time that measures the time between this moment, and a moment that does not exist. And that is my reason why I believe the argument is wrong. However, I am not saying I am absolutely sure about the error I have found. I could likely be wrong, but I wish to hear your comments about this, and hopefully your opinions on the matter.
 P: 32 The quote sounds like one of Zeno's paradoxes. You can google that for quite a few options as to how to resolve things like this. ----------------------------- One other idea that may be relevant is the fact that not all infinities are the same size. The most straight forward examples of this that I recall off hand are those that involve sets with an infinite number of members. Consider the set of all real numbers (recall that real numbers include all possible fractions as well as whole numbers) between 0 and 1. This set has an infinite number of members. Now compare that set with the set of all real numbers between 0 and 10. This set too is infinite but it is also ten times the size of the previous set. Likewise the set of whole numbers is an infinite subset of the infinite set of real numbers.
P: 1,797
Yes, but I don't see where the cardinality of the set of real numbers fit into this. I am not measuring the infinity of time with respect to any other thing. I don't think that whether time is continous or not matters in this case.

 This set too is infinite but it is also ten times the size of the previous set.
Now I think you are switching terms, the cardinality of a finite continous subset of the real numbers are not larger or smaller than any other I presume. The "length" of the interval from 0 to 10, which you perhaps are referring to, is obviously ten times larger than the interval from 0 to 1.
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I am aware that it is highly likely that my argument is flawed - or even totally false. Argumenting for such things is hard to keep rigorous. The very sentence that time has existed for an infinite amount of time seems pretty awkward, but my point is hopefully coming through.

I googled Zeno's paradoxes and I realise that I have read them before. They seem to have pretty "simple" solutions based on the fact that infinite series does not necessarily diverge. None of them is analogous to what I am talking about, much less my question.

By the way, the "quote" I am presenting is actually a creatonist's argument, which among other (ridiculous) arguments are supposed to prove the existance of God, and the fundamentalist christianity's view of the world.

P: 32
Is time infinite?

 Quote by Jarle Now I think you are switching terms, the cardinality of a finite continous subset of the real numbers are not larger or smaller than any other I presume. The "length" of the interval from 0 to 10, which you perhaps are referring to, is obviously ten times larger than the interval from 0 to 1.
Nice catch :) that was exactly what I said when I heard this. The whole numbers vs real numbers example is hazier, but still similar objections could be made most likely.

As for the rest, I don't usually bother to argue with creationists, it won't change anyone's mind and it annoys the creationist.

The problem with creationist arguments is that they are not honest. They start from the position and search over reality to find arguments or data that appear to support it, generally they then just disregard anything to the contrary.

I'm not interested in challenging the cherished beliefs of anyone, I'm interested only in learning new things about the universe. Since creationists and I have mutually exclusive goals for argument, neither of us can emerge satisfied.
P: 1,797
 Quote by Quatl Nice catch :) that was exactly what I said when I heard this. The whole numbers vs real numbers example is hazier, but still similar objections could be made most likely. As for the rest, I don't usually bother to argue with creationists, it won't change anyone's mind and it annoys the creationist. The problem with creationist arguments is that they are not honest. They start from the position and search over reality to find arguments or data that appear to support it, generally they then just disregard anything to the contrary. I'm not interested in challenging the cherished beliefs of anyone, I'm interested only in learning new things about the universe. Since creationists and I have mutually exclusive goals for argument, neither of us can emerge satisfied.
Ok, I thought of that the cardinality "rule" that " if there is a bijection between the sets of infinite order then they have the same cardinality" might not apply for real numbers, but I would only assume that it would. Nevertheless, it does not touch the matter.

I didn't say I was debating a creationist, I only said that I heard the argument from a creationist and it got me wondering. Oh, and I have experienced that debating creationists in the subject of metaphysics is useless too =)
P: 810
 Quote by Jarle "Assume time has no beginning, but that it has existed for an infinitely long time back. Then it would have taken an infinite amount of time until this moment. As an infinite amount of time will never end, this moment could never have occurred, and hence time cannot be infinite - it must have a beginning."
Who says that at any moment in a neighborhood of the present that an infinite interval of time has not passed?
 Emeritus Sci Advisor PF Gold P: 16,091 I should like to point out it's easy to: 1. Construct intervals of finite length that have no beginning and no end, 2. Construct intervals of infinite length that have a beginning, 3. Construct intervals of infinite length that have an end, and with a smidgin of mathematical sophistication, 4. Construct intervals of infinite length that have a beginning and an end Furthermore, given any interval at all without a beginning, it's easy enough to construct an 'idealized' point to serve as its beginning. Similarly for ends.
P: 1,797
 Quote by Tac-Tics Who says that at any moment in a neighborhood of the present that an infinite interval of time has not passed?
Hi, could you perhaps rephrase or explain that?

 Quote by Hurkyl I should like to point out it's easy to: 1. Construct intervals of finite length that have no beginning and no end, 2. Construct intervals of infinite length that have a beginning, 3. Construct intervals of infinite length that have an end, and with a smidgin of mathematical sophistication, 4. Construct intervals of infinite length that have a beginning and an end Furthermore, given any interval at all without a beginning, it's easy enough to construct an 'idealized' point to serve as its beginning. Similarly for ends.
Yes, analogous to the extended real number line. But any the beginning of any interval of infinite length, the end will never be reached. (analogous to that successive addition of numbers always will be finite).
P: 810
 Quote by Jarle Hi, could you perhaps rephrase or explain that?
The interval between the beginning of time and now could be infinite, and no contradiction arises.
Emeritus
PF Gold
P: 16,091
 Quote by Jarle Yes, analogous to the extended real number line. But any the beginning of any interval of infinite length, the end will never be reached.
I can't make out what was intended by this.

 (analogous to that successive addition of numbers always will be finite).
In what way is it analogous?

Before you answer, I would like to point out that the fact you cannot produce an infinite number by repeatedly applying (binary) addition to finite numbers says nothing about whether or not infinite numbers exist.
P: 1,783
 Quote by Jarle But any the beginning of any interval of infinite length, the end will never be reached. (analogous to that successive addition of numbers always will be finite).
Given the existence of infinite bounded sets, I would say this is not true.
P: 1,797
 Quote by franznietzsche Given the existence of infinite bounded sets, I would say this is not true.
If that is true, it degenerates the hypothetical argument quoted in my original post even more. Why do you mean that the existence of infinite bounded sets imply that an infinitely long interval will in some finite amount of time traverse from beginning to end, given that the "speed" that time traverses is constant? Or did you mean something else?
P: 1,783
 Quote by Jarle If that is true, it degenerates the hypothetical argument quoted in my original post even more. Why do you mean that the existence of infinite bounded sets imply that an infinitely long interval will in some finite amount of time traverse from beginning to end, given that the "speed" that time traverses is constant? Or did you mean something else?
I was referring to:
 Quote by Hurkyl I should like to point out it's easy to: 1. Construct intervals of finite length that have no beginning and no end, 2. Construct intervals of infinite length that have a beginning, 3. Construct intervals of infinite length that have an end, and with a smidgin of mathematical sophistication, 4. Construct intervals of infinite length that have a beginning and an end
I didn't say the intervals had any physical reality. I think I misunderstood the wording of your statement to mean that you could not have an infinite interval of the kind hurkyl described. I didn't think you were talking about actually walking from A to B along that interval.
 P: 3 I am a novice but it appears to me that you guys confuse actual infinites with potential infinites. We live in a finite universe, finite space, finite mater, and therefore finite time. While the idea of actual infinites can be postulated and theorized none can, in actuality, be experienced since we ourselves are finite beings. Care also has to be given, Jarle, if you are taking a materialist position, since this position would preclude metaphysics entirely. While I agree on whether time had a beginning or not does not prove nor disprove the God of the Bible, particularly, it would only substantiate that time did have a beginning. As we all know, whatever has a beginning has to have a cause, but to say what that cause is, once we hypothetically show that time did have a beginning, is a long way off from substantiating the God of the Bible. Other arguments have to be reasoned before one can go there. However, for now and for us, it would appear that time, space and matter did indeed have a beginning. To put forth ideas about other dimensions beyond our scope and ability to observe goes beyond the scientific method and undoubtedly enters the realm of metaphysics. However, if one claims to be a materialist, in the strictest definition of the word, can the materialist discuss issues of metaphysics since that person rejects any explanation of reality that does not fall within the scientific field of study and observation?
P: 649
 Quote by Jarle I have heard the argument that time must have a beginning (I know that discussion about time tends to become vague, because we have no definite definition of time, and that terms can overlap, (especially when talking about infinity) but I hope I make myself clear): "Assume time has no beginning, but that it has existed for an infinitely long time back. Then it would have taken an infinite amount of time until this moment. As an infinite amount of time will never end, this moment could never have occurred, and hence time cannot be infinite - it must have a beginning." (This is not quoted from anywhere) I believe this argument is flawed, because there exist no point on the time line such that there is a period of infinite length between that and this moment. Hence the second sentence of the argument uses a period of time that measures the time between this moment, and a moment that does not exist. And that is my reason why I believe the argument is wrong. However, I am not saying I am absolutely sure about the error I have found. I could likely be wrong, but I wish to hear your comments about this, and hopefully your opinions on the matter.

Time is techinacally not flowing, as far as physics is concerned. Hence a beginning and end are not valid scientific attributes of Time. I can find you a frame of reference where the universe is now just 2 minutes old, or another FOR where the universe is 1 million years old, etc. There is no preferred frame of reference outside of our subjective experience where we can meaningfully say - time is flowing. And yes, the situation with the explanation of the perception of Time flowing is rather uncomfortable.
 P: 3 I can appreciate your response and thank for responding. However, just because we, as in us in the here and now, do not have a frame of reference that does not mean, explicitly or implicitly, that time did not have a beginning. Nevertheless, I do have a question, and it is possible that my application or the application I have heard from others, is incorrect. It has to do with the second law of thermodynamics, more specifically entropy, of which I am sure you are more familiar than I. If everything is moving in a direction of usable energy to unusable, that is winding down (so to speak), does this not imply a beginning? If so, does this also imply a beginning of our time? Because that is what we are actually referring to, that is, time in our space. It does no good to speculate about other reference points or rather, planes of existence, because it has no bearing on our continuum. I have a hard time with an eternal universe, philosophically, as the universe has not the explanatory power for itself. That is, it cannot explain its own existence. The natural laws do not prescribe the existence of anything they only describe current predictable conditions. While this does not provide any “proofs” for a beginning it can give me a reference point to work from, nevertheless, deductive is so much more preferred rather than inductive, but that is all we have to work from. Furthermore, if the universe is moving toward the direction of heat death as the law of entropy dictates, then what could explain the “rewinding” of an eternal universe? For that matter, what kind of explanation is there for the initial “jump start” of the universe? Are you stating that the universe itself, that is, matter, may have had a beginning but time did not? (No sarcasm intended, a question in earnest.) Because we know based on the second law that the clock has been ticking for all matter, so I assumed a beginning not just for matter but also for time as it relates to space and matter.
 PF Gold P: 4,287 I don't think the question even makes sense. It's like asking "Is distance infinite" or "is mass infinite" in that distance, mass, and time are abstract concepts defined for measurement; they're dimensions. You can ask whether a particular distance is infinite, or a particular mass, or a particular time, to which the answer will most certainly be "no".
P: 649
 Quote by Schnoodle I can appreciate your response and thank for responding. However, just because we, as in us in the here and now, do not have a frame of reference that does not mean, explicitly or implicitly, that time did not have a beginning.

No, we do have a frame of reference, however this FOR is not in any way privileged over all the others. You speak of beginnings and ends but in relativity there are many many FOR's where the "universe" has not begun yet(e.g. photons emitted at the BB).

 Nevertheless, I do have a question, and it is possible that my application or the application I have heard from others, is incorrect. It has to do with the second law of thermodynamics, more specifically entropy, of which I am sure you are more familiar than I. If everything is moving in a direction of usable energy to unusable, that is winding down (so to speak), does this not imply a beginning?

Yes, it does imply a beginning, however putting an observation from a particular FOR as the "True" one over all the others is pretty anthropocentric. From our "point of view", the universe is 13.7 b. years old, however this isn't the only available "point of view".

 Because we know based on the second law that the clock has been ticking for all matter, so I assumed a beginning not just for matter but also for time as it relates to space and matter.

The clock ticking is one of those human observations which refuses to be framed by our scientific theries and methods. If i had to speculate, i'd say it 's probably consciousness-related.

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