Can the Universe repeat itself?

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In summary, the question posed by the philosophy professor is whether the universe can repeat itself given an infinite amount of time, considering that there is a finite number of matter in the universe and a finite number of ways that it can arrange itself. However, an article in Sci Am points out that an infinite universe is not necessary for this to happen. Poincare's Recurrence Theorem suggests that, with a finite number of particles and infinite time, the state of the universe will eventually repeat itself. This raises questions about the nature of the universe and the possibility of an endless loop. However, the concept of "finite complexity" is important in this scenario, as it requires truly atomic building blocks, atomic positions in space and time, and a
  • #36
DaveC426913 said:
I am not convinced this is true.Seems, to me that, once the highest entopic state is reached, and all stars have cooled to ambient temperature, there is no way of reversing the process. The universe could stay in this state infinitely long without ever returning to a lower entropy state.

True, there may be ways the universe could reverse its cycle, such as the Big Crunch, but that is not to say these are inevitable futures.

I myself am not completely convinced this would necessarily be true, but there are ways it could possibly be. For instance, since the universe is probabilistic in nature, there could be quantum fluctuations that would disrupt a universe in an entropic state, given an infinite amount of time to do so. These fluctuations could lead to an uneven distribution of matter/energy. Gravity could eventually start to reform the matter into clumps, and the whole process would repeat.
 
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  • #37
I read a book my dad received from college when he earned his degree as an FBI field officer. The book was about homicide/suicide investigation. It said that when you arrive at a crime scene you shouldn't touch anything there because it will never be able to get back to it's original position. The universe could repeat itself in a mathematical sense. Take (this is just an example) the possibility of it happening to be 1 / 99999999999999999999. So as you can see, even though the chances are slim, according to the numbers, it could happen.(according to the numbers) I'm sure the possibility of it happening is much more unlikely than as displayed in my example. So by numbers, it is possible, but in the physical and realistic realm it is impossible. Just think about it for a minute or two. All of the books in the world would have to all be on the same page. All of the cars on the road would have to be on the same road and at the exact place in the road. All of the people would have to be in the same place and position. It's almost like a person who gets shot and their chances of living are 0.0003 percent. By numbers it seems slightly possible but if the percentage of it happening is that low it won't happen in the physical and realistic realm.
 
  • #38
Evolver said:
I myself am not completely convinced this would necessarily be true, but there are ways it could possibly be. For instance, since the universe is probabilistic in nature, there could be quantum fluctuations that would disrupt a universe in an entropic state, given an infinite amount of time to do so. These fluctuations could lead to an uneven distribution of matter/energy. Gravity could eventually start to reform the matter into clumps, and the whole process would repeat.
Yes, again: I'm not saying it must be this way, I'm simply refuting the unilateral claim that "infinite time means infinite cycles". There are plausible scenarios where that is false.
 
  • #39
JerryClower said:
Just think about it for a minute or two. All of the books in the world would have to all be on the same page.
What boggles me is that, between this point in space/time and that point in space/time, there is a state where everything is identical except just one page of one book is one page off. And there's also a state where that one page iof that one book is two pages off, etc.

Like the inifinite monkeys at infinite typewriters probabilistically writing Shakespeare's Hamlet, there is a monkey somewhere that wrote Hamlet perfectly except for one wrong letter. And another that wrote it perfectly except for two wrong letters.

Infinity is a bogglnig concept.
 
  • #40
DaveC426913 said:
Yes, again: I'm not saying it must be this way, I'm simply refuting the unilateral claim that "infinite time means infinite cycles". There are plausible scenarios where that is false.

True, my statement was a bit too broad to be fully effective.
 
  • #41
DaveC426913 said:
Like the inifinite monkeys at infinite typewriters probabilistically writing Shakespeare's Hamlet, there is a monkey somewhere that wrote Hamlet perfectly except for one wrong letter. And another that wrote it perfectly except for two wrong letters.
Did that actually happen or is that some sort of legend?
 
  • #42


FlowerPUA said:
[..] It is to my understanding that the universe has a finite (1x10^70) number of atoms spread out over a finite distance which is expanding into an infinite amount of space. [..]

Wrong.
1. You can only approx. the number of atoms in the observable universe. We don't know how much larger the whole universe is than the observable universe, I hold it that the whole universe is infinite.
2. The universe is not expanding into infinite space, it is space-time itself expanding.
 
  • #43
JerryClower said:
Did that actually happen or is that some sort of legend?

No it never happened, it would take far longer than any monkey could live. It would likely take longer than the universe has even existed.

It's an oft cited example of the inevitable byproducts of speaking about infinity scenarios. Given an infinite amount of time, a random monkey would inevitably type out the full work of Shakespeare's Hamlet (or any other work for that matter), by simply typing in an arbitrary manner. Probabilistically speaking, it would take a very very very long time, but if you had an infinite amount of time to wait (or an infinite amount of typing monkeys) it would not only happen once, but an infinite amount of times.

The monkey is simply used as example to illustrate that there would be only random keystrokes, and through pure probabilities, would at some point have typed out the entire play, perfectly.
 
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  • #44
If the universe were to for some reason undergo a Poincaré recurrence so that for example everything was exactly as it was on January 1, 2000, would events from that point be guaranteed to take the same path as now for example I'd always as this question here on May 20 2010? If this is the case then it's quite close to Nietzsche's Eternal return if not then the time before an exact repetition would be much larger.
 
  • #45
gravenewworld said:
I remember my philosophy professor asking us this question- Take all the matter in the universe, it is an ungodly number, however it is finite. Given that there is a finite number of matter in the universe, there is only a finite number of ways that all the matter can arrange itself. So is it possible that the universe can repeat itself given an INFINITE amount of time? Would it be possible for all the matter that composes your body right now to arrange itself again later on trillions upon trillions of years from now in the same exact order so that you would exist again?

It is my understanding that ideas like this are what fuels theories of multiple universes. For instance, a universe that is infinite, or at least sufficiently large in size, will have exact copies of you and I living in drastically different places. Scientific American released a nice explanation of the various types of multiverse theories and how the question you mention has fueled the idea and research of this possibility. It's called Parallel Universes.
 
  • #46


FlowerPUA said:
1. The “heat death” hypothesis of the universe appears to be flawed. With no kinetic energy in the universe it would be a “frozen wasteland”. However a finite mass, separated by a finite distance would still feel a small force of gravity over the immense distances. This force, however small, on an infinite timeline would lead to collisions, and ultimately all the mass converging again onto one point, perhaps for another “big bang”.
From what I've heard gravity's speed is light speed in vacuum, so if expansion of space between particles surpasses the speed of light(and it is space itself that is expanding it's not merely the particles moving away, but that even if they were not moving, the space between them is increasing.), gravitational attraction ceases.


3. It was mentioned above that we would be separated a distance of 1x10^120 metres from a repetition. I don’t really understand this concept at all. It is to my understanding that the universe has a finite (1x10^70) number of atoms spread out over a finite distance which is expanding into an infinite amount of space. Are you suggesting that there could be more mass, from yet more “big bangs” in the same universe?
From my understanding when people mention numbers it is of the visible universe, not the whole universe. It is unknown if the big bang produced an infinity of matter. It is also said to not be 'expanding into' anything, that is there is nothing into which it is expanding, there is supposed to be no spacetime prior to the moment of the big bang into which something could have expanded into... spacetime is supposed to have come into being at the moment of the big bang.
 
  • #47
When speculating about recurrence, remember that there is a big difference between a static system, like gas particles trapped in a flask, and the expanding universe. Over an infinite time in an expanding, cooling, universe, accidentally recreating the initial conditions, or even just earlier states, becomes infinitely unlikely.

At heat death, any remaining matter would be so spread out that particles would be beyond each others event horizons. So even QM couldn't magic them back together.
 
  • #48
I really hope the universe does not repeat itself. The thought of living for eternity with no escape is terrifying! I can't imagine what it's like to be dead, only alive. So maybe our perception is always going to be alive, in this same body. But then if the universe repeated itself, how did space-time even exist in the first place?
 
  • #49
Overman said:
I really hope the universe does not repeat itself. The thought of living for eternity with no escape is terrifying!
This has nothing to do with you living for eternity. You will still die. A bajillion years from now, if all the atoms in the universe find themselves in a configuration just like it was a bajillion years ago - that won't be you; it will just be a bunch of atoms arranged into a person who is like you.
 
  • #50
DaveC426913 said:
This has nothing to do with you living for eternity. You will still die. A bajillion years from now, if all the atoms in the universe find themselves in a configuration just like it was a bajillion years ago - that won't be you; it will just be a bunch of atoms arranged into a person who is like you.

I'm pretty sure it would be you. You just wouldn't know it was you.
 
  • #51
zomgwtf said:
I'm pretty sure it would be you.
Well, semantics aside, the OP was worried about being trapped for eternity. This is a misconception.
 
  • #52
DaveC426913 said:
This has nothing to do with you living for eternity. You will still die. A bajillion years from now, if all the atoms in the universe find themselves in a configuration just like it was a bajillion years ago - that won't be you; it will just be a bunch of atoms arranged into a person who is like you.

Yea but you have no perception of those bajillion years, so essentially the next thing you would perceive after dying is being born again as a baby into the same person to repeat the same life, over and over. :|
 
  • #53
Overman said:
Yea but you have no perception of those bajillion years, so essentially the next thing you would perceive after dying is being born again as a baby into the same person to repeat the same life, over and over. :|

Wrong.

If our universe were to be repeated exactly the same way then assuming everything is predetermined (including our freewill) then you would at the exact point in time along the life of the universe be posting this rediculous comment. You would have been born the same way and you would grow up to be the same person. There wouldn't be any perception of being born again because this you(the one in our universe) isn't being born again. A NEW you is being born for the first time(in a different universe).

This of course assumes, as I said, that everything is predetermined including our choices etc..

So to clarify you are wrong in your assumption that it would be the same person to repeat the same life, over and over again in the context you are giving. I can now see where daves comment comes from.
 
  • #54
DaveC426913 said:
Well, semantics aside, the OP was worried about being trapped for eternity. This is a misconception.

:rofl: I see that now. I was mostly just poking at the weirdness of the situation but this guy does have a pretty far fetched idea here doesn't he?
 
  • #55
zomgwtf said:
Wrong.

If our universe were to be repeated exactly the same way then assuming everything is predetermined (including our freewill) then you would at the exact point in time along the life of the universe be posting this rediculous comment. You would have been born the same way and you would grow up to be the same person. There wouldn't be any perception of being born again because this you(the one in our universe) isn't being born again. A NEW you is being born for the first time(in a different universe).

This of course assumes, as I said, that everything is predetermined including our choices etc..

So to clarify you are wrong in your assumption that it would be the same person to repeat the same life, over and over again in the context you are giving. I can now see where daves comment comes from.

That's not what I meant. I know there would be no link from this universe to the next, and you cannot perceive being born again. But I'm saying if there is an identical universe in the future, then death is never going to be the end of our life. We will always be perceiving something, not nothing. So technically, we will perceive ourselves as alive, for eternity. Which is scary.
 
  • #56
Overman said:
That's not what I meant. I know there would be no link from this universe to the next, and you cannot perceive being born again. But I'm saying if there is an identical universe in the future, then death is never going to be the end of our life. We will always be perceiving something, not nothing. So technically, we will perceive ourselves as alive, for eternity. Which is scary.

No I understood exactly what you meant, and it's wrong. You from this universe will never perceive living in any other universe. The other you (in the other universe) will perceive everything. They are 'different' yous, and you certainly will die in this universe and that's the end of you.
 
  • #57
zomgwtf said:
No I understood exactly what you meant, and it's wrong. You from this universe will never perceive living in any other universe. The other you (in the other universe) will perceive everything. They are 'different' yous, and you certainly will die in this universe and that's the end of you.

Ok yes, they are in different universes in a different timezone, there is no connection.

But imagine yourself in the previous universe saying that comment, then he(you) went and died somehow, but here you are, typing it again. You don't remember anything from that universe obviously, but everything about that person was identical to you. Think of the massive timescale of the universe, and think that you are alive in the smallest fraction of existence right now. Subjectively, you cannot not exist! You will always perceive being alive. If this theory is true. And if determinism exists then you will always do the exact same thing. So we are like vehicles for a number of predetermined acts. We are like along for the ride, with no free will, and no end, to this eternity.

In regards to eternal return, Nietzsche calls the idea "horrifying and paralyzing", and says that its burden is the "heaviest weight" imaginable.

You obviously don't understand it or feel it the same way I do, and that's good that you don't!
 
  • #58
Overman said:
Subjectively, you cannot not exist!
You are just playing with language.

Just because something is an identical copy of something else, doesn't mean they are the same thing. For instance, you could make an identical copy of yourself and then have a conversation with yourself. That doesn't mean that, subjectively, you are both people, even if both thinks they are the original. It just means you have a similar composition and history.

The issue of identity gets murky when you start talking about replacing parts of a thing. In this case, 'thingness' becomes primarily a matter of continuity. But there is no continuity in your scenario, only similarity between two different things.

And Nietzsche was being metaphorical. Eternal return, was about embracing the life you have to such an extent that you would 'choose' to live every moment over again, forever. It was an affirmation of life.
 
  • #59
Overman said:
In regards to eternal return, Nietzsche calls the idea "horrifying and paralyzing", and says that its burden is the "heaviest weight" imaginable.
The question is though, would the other "you" be guaranteed to make exactly the same choices you did this life? If not then you will have lived the same life in every way you can have possibly lived it an infinite number of times.
 
  • #60
JoeDawg said:
The issue of identity gets murky when you start talking about replacing parts of a thing. In this case, 'thingness' becomes primarily a matter of continuity. But there is no continuity in your scenario, only similarity between two different things.

Thank you JoeDawg, I was trying to think of the term last night but my mind was drawing a complete blank. Continuity. Very important in this situation and was what I was trying to explain without using the term because I had forgot it. :rofl:

@overman It doesn't matter if this other universe is 100% the same and 100% predetermined. The problem is continuity of your identity between universes. This doesn't exist. I think you are confused about what would be occurring in such a scenario. First of all, you shouldn't take discomfort in the possibility that you exist in a different universe 100% identical to how you are now, because you have no idea if this is true. Second of all if it was true both you's would have no idea. Third of all even if you did believe it to be true you still have to concede there is absolutely no connection between both persons. Their identities are different in the sense that they 'different yous'.
 
  • #61
Overman said:
But imagine yourself in the previous universe saying that comment, then he(you) went and died somehow, but here you are, typing it again. You don't remember anything from that universe obviously, but everything about that person was identical to you. Think of the massive timescale of the universe, and think that you are alive in the smallest fraction of existence right now. Subjectively, you cannot not exist! You will always perceive being alive.

There is no logic to the above. None of the statements follow logically from the previous statement. They are all non sequitur.
 
  • #62
JoeDawg said:
You are just playing with language.

Just because something is an identical copy of something else, doesn't mean they are the same thing. For instance, you could make an identical copy of yourself and then have a conversation with yourself. That doesn't mean that, subjectively, you are both people, even if both thinks they are the original. It just means you have a similar composition and history.

The issue of identity gets murky when you start talking about replacing parts of a thing. In this case, 'thingness' becomes primarily a matter of continuity. But there is no continuity in your scenario, only similarity between two different things.

And Nietzsche was being metaphorical. Eternal return, was about embracing the life you have to such an extent that you would 'choose' to live every moment over again, forever. It was an affirmation of life.

I see what you mean. That makes sense with the whole clone scenario. I guess it is hard to imagine ever being dead, since I haven't been dead yet.

I was watching a video last night on TED, who rejects the idea of a cyclic universe.
http://www.ted.com/talks/sean_carroll_on_the_arrow_of_time.html [Broken]

This guy was talking about how there are no entropy fluctuations, and that entropy will always increase in an ever expanding universe. But he did point out that when entropy is high enough, points in the universe can break out of the universe into low entropy (because this breaking off would still be increasing the overall entropy). This low entropy state would then cause another big bang, making a baby universe (which I don't think is identical to the previous one). And he said this occurs in the opposite mirrored direction too.
 
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  • #63
Overman said:
http://www.ted.com/talks/sean_carroll_on_the_arrow_of_time.html [Broken]

I can't really speak to the physics of it, but I find the whole 'multiverse' idea unsatisfying.
It strikes me as too convenient.
Its like the big bang/crunch idea, which made perfect sense, until we found out it was wrong.

Interesting ideas though.
 
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  • #64
Can anyone actually explain the multiverse concept to me in a way that doesn't violate the objects not existing ontop of each other thing?
 
  • #65


flashprogram said:
... spacetime is supposed to have come into being at the moment of the big bang.
At what moment? A moment at which there was not (yet) time?
You have to re-learn Big Bang Theory, simply it does not state that the event of the Big Bang was the beginning of space time and there are good theories out there that explain why the Big bang happened and solved some previously unexplainable puzzels, like for instance cosmological inflation, that does not require you to introduce something like 'beginning of time' (imho such is a a misnomer, since outside of time, you can not refer to begin, since that already assumed a time concept).
 
  • #66
magpies said:
Can anyone actually explain the multiverse concept to me in a way that doesn't violate the objects not existing ontop of each other thing?

You should study the topic of multiverse in the context of a theory that comes up with that idea. Like for example string theory or cosmological inflation, where it comes out naturally (inflation just continues in other parts of the universe eternally).
 
  • #67
I am the center of my visible universe, you are the center of your visible universe, put all of us together we share a common visible universe. A multiverse that is not one on top of another but over lap each other with a common center. :smile:
 
<h2>1. Can the Universe repeat itself?</h2><p>This is a common question that has been debated by scientists and philosophers for centuries. The answer is that we do not know for sure. Some theories, such as the cyclic model, suggest that the universe goes through cycles of expansion and contraction, potentially leading to repetition. However, there is currently no concrete evidence to support this idea.</p><h2>2. What evidence is there for the universe repeating itself?</h2><p>As mentioned, there is no direct evidence that the universe repeats itself. However, there are some patterns and cycles that can be observed in the universe, such as the changing of the seasons, the orbits of planets, and the life cycles of stars. Some scientists argue that these patterns could potentially support the idea of repetition, but it is still just speculation at this point.</p><h2>3. Is the concept of the universe repeating itself scientifically valid?</h2><p>This is a difficult question to answer definitively. While some theories and ideas suggest the possibility of repetition, there is currently no scientific proof or consensus on the matter. It is still a topic of debate and speculation in the scientific community.</p><h2>4. How does the concept of the universe repeating itself relate to the concept of time?</h2><p>The idea of the universe repeating itself is closely tied to the concept of time. If the universe were to repeat itself, it would suggest that time is cyclical rather than linear, as we currently understand it. However, as mentioned, there is no concrete evidence to support this idea, so it is impossible to say for sure how it would impact our understanding of time.</p><h2>5. Could we ever know if the universe repeats itself?</h2><p>This is a difficult question to answer, as it ultimately depends on whether or not the universe does in fact repeat itself. If it does, it is possible that we could eventually gather enough evidence and understanding to prove it. However, if the universe does not repeat itself, it may be impossible for us to ever know for sure. It is a topic that will likely continue to be explored and debated by scientists for years to come.</p>

1. Can the Universe repeat itself?

This is a common question that has been debated by scientists and philosophers for centuries. The answer is that we do not know for sure. Some theories, such as the cyclic model, suggest that the universe goes through cycles of expansion and contraction, potentially leading to repetition. However, there is currently no concrete evidence to support this idea.

2. What evidence is there for the universe repeating itself?

As mentioned, there is no direct evidence that the universe repeats itself. However, there are some patterns and cycles that can be observed in the universe, such as the changing of the seasons, the orbits of planets, and the life cycles of stars. Some scientists argue that these patterns could potentially support the idea of repetition, but it is still just speculation at this point.

3. Is the concept of the universe repeating itself scientifically valid?

This is a difficult question to answer definitively. While some theories and ideas suggest the possibility of repetition, there is currently no scientific proof or consensus on the matter. It is still a topic of debate and speculation in the scientific community.

4. How does the concept of the universe repeating itself relate to the concept of time?

The idea of the universe repeating itself is closely tied to the concept of time. If the universe were to repeat itself, it would suggest that time is cyclical rather than linear, as we currently understand it. However, as mentioned, there is no concrete evidence to support this idea, so it is impossible to say for sure how it would impact our understanding of time.

5. Could we ever know if the universe repeats itself?

This is a difficult question to answer, as it ultimately depends on whether or not the universe does in fact repeat itself. If it does, it is possible that we could eventually gather enough evidence and understanding to prove it. However, if the universe does not repeat itself, it may be impossible for us to ever know for sure. It is a topic that will likely continue to be explored and debated by scientists for years to come.

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