Death of Universe: Is a New Big Bang Possible?

[Nernico]

How will universe die? Energy can't be created or destroyed so is that possible that the energy of this dead universe could create a new big bang?

 

[Ryan_m_b]

Hi there Nernico. You are right in saying that energy cannot be created or destroyed however thanks to entropy the universe is heading towards its maximum state of disorder. This essentially means eventually the energy will be spread out evenly, it is currently thought that this will lead to heat death in about 10¹⁰⁰ years.

There are other ideas regarding the http://en.wikipedia.org/wiki/Fate_of_the_universe" (creating a new universe) but as I understand it the heat death is the only idea that has evidence to support it.

 

[Tanelorn]

Hi Nernico, my understanding of the current theory is that all matter and energy eventually leaves the universe the same way as it entered, through a singularity or singularities (as in black holes).

 

[bcrowell]

Hi Nernico, my understanding of the current theory is that all matter and energy eventually leaves the universe the same way as it entered, through a singularity or singularities (as in black holes).

I don't think that's right. The WP article that ryan linked to is actually pretty good.

 

[Tanelorn]

Ben last time I looked at this was quite a while ago so maybe I am out of date. The last few sections here is how I recall the end:

http://www.universetoday.com/11430/the-end-of-everything/


much regards,
Chris

 

[Chalnoth]

How will universe die?

Most likely heat death. Wikipedia has a good breakdown:
http://en.wikipedia.org/wiki/Future_of_an_expanding_universe

Energy can't be created or destroyed so is that possible that the energy of this dead universe could create a new big bang?

This isn't entirely true. There is no concept of global energy conservation in General Relativity. This is a good read on the subject:
http://www.desy.de/user/projects/Physics/Relativity/GR/energy_gr.html

In the end, all matter energy will eventually become radiation energy. And radiation energy tends to dilute as the fourth power of the scale factor, so that in an expanding universe, the total energy in a set comoving volume decreases with time (a comoving volume is one that expands along with the expansion of the universe). In these coordinates, the total energy of a comoving volume of the universe tends towards zero.

 

[bcrowell]

Ben last time I looked at this was quite a while ago so maybe I am out of date. The last few sections here is how I recall the end:

http://www.universetoday.com/11430/the-end-of-everything/

The article doesn't support what you said in #3, that "all matter and energy eventually leaves the universe the same way as it entered, through a singularity or singularities (as in black holes)." It talks about converting baryonic matter into photons through hawking radiation.

 

[bcrowell]

In the end, all matter energy will eventually become radiation energy.

I don't think this is quite right. There is no reason to believe that every single atom in the universe will get consumed by a black hole and then recycled into Hawking radiation. This is actually one of the problems with Penrose's CCC. To make CCC work, he needs 100% conversion of baryonic matter into photons, but theory doesn't offer any reason to believe that it will be 100%.

 

[Ryan_m_b]

I don't think this is quite right. There is no reason to believe that every single atom in the universe will get consumed by a black hole and then recycled into Hawking radiation. This is actually one of the problems with Penrose's CCC. To make CCC work, he needs 100% conversion of baryonic matter into photons, but theory doesn't offer any reason to believe that it will be 100%.

Would an individual atom not eventually decay into something else or are they perpetually stable? I'm not proposing that it will decay I genuinely don't know.

 

[bcrowell]

Would an individual atom not eventually decay into something else or is it perpetually stable? I'm not proposing that it will decay I genuinely don't know.

There is speculation about proton decay, http://en.wikipedia.org/wiki/Proton_decay , but there's no actual evidence for it.

Even if proton decay exists, there are other forms of matter such as neutrinos that are stable as far as we know, and in the far future you can also have individual electrons that end up isolated inside their own cosmological event horizons forever.

There's a brief discussion of this kind of thing in the following paper by Penrose on CCC: http://epaper.kek.jp/e06/PAPERS/THESPA01.PDF

 

[Chalnoth]

I don't think this is quite right. There is no reason to believe that every single atom in the universe will get consumed by a black hole and then recycled into Hawking radiation.

Talking with the high energy physics people, proton decay is generally expected to be inevitable. That is why all matter will eventually become radiation.

This is actually one of the problems with Penrose's CCC. To make CCC work, he needs 100% conversion of baryonic matter into photons, but theory doesn't offer any reason to believe that it will be 100%.

The main problem is that there is no physical mechanism.

 

[Tanelorn]

Ben, all matter ending up in black holes is one of the possibilities discussed here and it stuck with me for decades. Perhaps it is no longer considered likely. Dark energy expansion of the universe may help prevent it.

"Chunks of matter and binary black dwarfs will merge together creating new black holes, and these black holes will be consumed by even larger black holes. It might be that in the far future, all matter will exist in a few, truly massive black holes."

http://www.universetoday.com/11430/t...of-everything/

 

[bcrowell]

Talking with the high energy physics people, proton decay is generally expected to be inevitable. That is why all matter will eventually become radiation.

Sorry, but I'm not buying it based on your secondhand impression that other people think it's inevitable. In any case, it has nothing to do with the arguments about neutrinos, or electrons isolated inside cosmological horizons. There's also the issue of dark matter, which is probably stable as well, although we know almost nothing about it.

The main problem is that there is no physical mechanism.

I wasn't pointing you to the paper to say that I think CCC is right. I was pointing you to the paper because it discusses the reasons why it is incorrect to claim that all matter will become radiation. Penrose would like all matter to become radiation, because it's necessary if he wants CCC to work. Nevertheless he honestly surveys what we know about the question, and concludes that based on current knowledge of particle physics, it won't happen. For this reason, one of the predictions he was originally pushing as part of CCC was nonstandard particle physics that would allow what you're claiming to be true.

 

[bcrowell]

Ben, all matter ending up in black holes is one of the possibilities discussed here and it stuck with me for decades. Perhaps it is no longer considered likely. Dark energy expansion of the universe may help prevent it.

"Chunks of matter and binary black dwarfs will merge together creating new black holes, and these black holes will be consumed by even larger black holes. It might be that in the far future, all matter will exist in a few, truly massive black holes."

http://www.universetoday.com/11430/t...of-everything/

Note the "it might be." And again, this does not support your statement that "all matter and energy eventually leaves the universe the same way as it entered, through a singularity or singularities (as in black holes)." The mass-energy recycled through Hawking radiation does not "leave the universe." For that matter, nothing "entered" the universe "through" the big-bang singularity.

Tanelorn and Chalnoth, let's try to raise the level of discussion here. I've given you guys a reference to an actual scientific paper. You've given me statements that you think other people think X is true, and to a popular-level article that doesn't support your claim.

 

[bcrowell]

I turned up a good review article on this topic: Adams and Laughlin, A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects, , Rev.Mod.Phys.69:337-372,1997, http://arxiv.org/abs/astro-ph/9701131

"Thus, unless the dark matter particles themselves
decay into radiation, it seems that enough non-baryonic dark matter should survive to keep the universe
matter dominated at all future epochs; in addition, the leftover electrons and positrons will help prevent
the universe from becoming radiation dominated" (p. 38)

 

[Tanelorn]

Ben, I have no proof, it was just one of several possible endings that I read in the popular press, possibly even before Hawking radiation was proposed, and to me at least, the one that seems the most elegant. ie. Matter and energy entered the universe via a singularity, and at the end leaves the universe via a singularity. As I said I am probably well out of date, but I will read the paper you linked soon. Just started reading it, it is impressive.

Would you not agree however that the orbit of all the stars in our galaxy over an extremely long time will eventually decay until the central black hole makes its kill?

 

[bcrowell]

Ben, I have no proof, it was just one of several possible endings and to me at least the one that seems the most elegant.

Would you not agree however that the orbit of all the stars in our galaxy over an extremely long time will eventually decay until the central black hole makes its kill?

You don't have to reinvent the wheel. Read the paper by Adams and Laughlin.

The Adams/Laughlin review dates back to before we knew about the nonzero cosmological constant. Here is a discussion that's more up to date but less detailed:

Baez, J., 2004, "The End of the Universe.", http://math.ucr.edu/home/baez/end.html

 

[Tanelorn]

Thanks Ben, I read that entirely. It seems that matter and energy never leaves the universe at all then. Perhaps it always was here then before the BB.

He does also mention that Cosmology is a fast moving science at the moment. In my design / integration phase in work we say that a product is still no where near ready to ship whilst it still rapidly undergoing mods due to bugs. If we consider how many cosmological theories have been proposed since the ancients first thought the Earth was the center of the universe, then what is the chance that the latest theories are correct? However, I agree that the latest is probably the best we have.

 

[Chalnoth]

Sorry, but I'm not buying it based on your secondhand impression that other people think it's inevitable.

The way I understand it, the argument goes that in order to have baryogensis, you need baryon number to not be exactly conserved. And if baryon number isn't exactly conserved, protons will, at some point, decay.

There's also the issue of dark matter, which is probably stable as well, although we know almost nothing about it.

Yes, but the dark matter is expected to have been produced in equal parts matter and anti-matter, meaning it will eventually annihilate.

 

[bcrowell]

Yes, but the dark matter is expected to have been produced in equal parts matter and anti-matter, meaning it will eventually annihilate.

This would contradict the statement by Adams and Laughlin that I quoted in #15. Even if dark matter is an equal mix of particles and antiparticles (which I doubt can be stated with any certainty right now), there is the fact that some individual particles find themselves isolated inside their own cosmological horizons. This is discussed in both the Penrose paper and the Baez page.

 

[Haelfix]

Even if there was no Beyond the standard model theory out there (where dimension 6 terms are often generated naturally) proton decay would occur, given long enough timeframes, by Sphaeleron decay and other nonpertubative effects.

The timeframes involved are astronomical though, albeit small relative to the recurrence time of a DeSitter end state.

 

[Chalnoth]

This would contradict the statement by Adams and Laughlin that I quoted in #15. Even if dark matter is an equal mix of particles and antiparticles (which I doubt can be stated with any certainty right now), there is the fact that some individual particles find themselves isolated inside their own cosmological horizons. This is discussed in both the Penrose paper and the Baez page.

Yes, well, one particle in a sphere roughly 16 billion light years in radius is close enough.

 

[bcrowell]

Yes, well, one particle in a sphere roughly 16 billion light years in radius is close enough.

Close enough to...? Close enough so that...?

The point is that the universe is predicted to be matter-dominated, not radiation-dominated. It's the opposite of what you claimed, which was that all matter would be converted to radiation.

 

[Chalnoth]

Close enough to...? Close enough so that...?

The point is that the universe is predicted to be matter-dominated, not radiation-dominated. It's the opposite of what you claimed, which was that all matter would be converted to radiation.

Well, dark energy-dominated. What I was basically saying is that matter gets converted to radiation, which then redshifts away to irrelevance.

 

[Tanelorn]

So what we are saying then is that nothing in this universe is eternal, all matter and energy just disperses and fades away into insignificance, perhaps like wiping the board clean as it was before the last BB, ready and waiting for something to create another BB?

It is also interesting that this stage in the life cycle of our universe is by no means the main stage but is very temporary in comparison. Any life that still exists later on had better be pretty frugal with its energy usage.


Ben, one other point in that link you provided. I am havng a hard time visualising how most of the stars will eventually be ejected from old eliptical galaxies.

 

[Ryan_m_b]

So what we are saying then is that the nothing in this universe is eternal, all matter and energy just disperses and fades away into insignificance, perhaps like wiping the board clean as before the last BB, ready and waiting for something to create another BB?

I don't think anyone here is saying that. The notion of "before" the Big Bang does not make sense in contemporary physics, we can only probe back to the http://en.wikipedia.org/wiki/Planck_epoch" . Whether or not time existed 'before' then is unknown.

As for creating another Big Bang I would advise you to read some of the sites linked in this thread. Currently we do not have a comprehensive understanding of the mechanism underlying the Big Bang, at the moment the ultimate fate of the universe looks to be http://en.wikipedia.org/wiki/Heat_death_of_the_universe" .

 

[Tanelorn]

Ryan I think I was also trying to describe heat death, just couldn't think of the term.

Would I be correct in saying that a fresh supply of Hydrogen would keep up star formation and thus a reasonably steady state universe? Is there any scenario where a small but endless supply of fresh hydrogen could continuouslly be produced from (just brainstorming here) galactic voids, dark energy, dark matter, spontaneous matter creation or some other method? I don't know if such a thing is so outragaous when we consder that the entire universe was created spontaneously.

 

[Ryan_m_b]

Ryan I think I was also trying to describe heat death, just could think of the term.

I got that part of your statement, it was the latter part "perhaps like wiping the board clean as it was before the last BB, ready and waiting for something to create another BB?" that I was objecting to.

Would I be correct in saying that a fresh supply of Hydrogen would keep up star formation and thus a reasonably steady state universe?

Eventually the mass that this hydrogen is adding to the universe may eventually result in a http://en.wikipedia.org/wiki/Big_Crunch" . I'm sure there are other, bigger objections here too

Is there any scenario where a small but endless supply of fresh hydrogen could continuouslly be produced from (just brainstorming here) galactic voids, dark energy, dark matter, spontaneous matter creation or some other method? I don't know if such a thing is so outragaous when we consder that the entire universe was created spontaneously.

Current understanding is not that the universe was "created" nor was it "spontaneous". As I have already explained we do not have a comprehensive understanding for why the Big Bang occurred but there is no reason to suggest that everything popped into existence, it is my understanding that the universe most likely began as a singularity with all the matter and energy that we have now residing in one place. No extra mass or energy was created. As the the matter creation you are asking about such a thing would violate http://en.wikipedia.org/wiki/Conservation_of_energy" . To specifically address your question'

Galactic Voids - are empty space, there is no reason to think that this would allow matter to pop into existence.
Dark energy - the proposed, homogeneous energy in the universe that is facilitating it's expansion, whilst no comprehensive understanding of this exists there is no reason to think that this would allow matter to pop into existence.
Dark matter - the proposed exotic matter that interacts with normal matter in a limited manner. It accounts for all the "missing mass" in the universe. Again there is no reason to think that this would allow matter to pop into existence

 

[Tanelorn]

Ryan I do recall reading that some matter is spontaneously produced in free space. Was it electron positron pairs?

PS I like your signature, Asimov's Foundation series is excellent, Galaxia and so on. Of course the Earth is flat from my perspective and the Earth is round from the moons perspective. This makes me wonder if our cosmological pespective is good.

 

[Ryan_m_b]

Ryan I do recall reading that some matter is spontaneously produced in free space. Was it electron positron pairs?

You may have read about http://en.wikipedia.org/wiki/Virtual_particle" , even if a virtual particle were to become real the process would still obey conservation of energy. I should have clarified that the sum total of energy in the universe remains the same no matter what.

 

[Chalnoth]

You may have read about http://en.wikipedia.org/wiki/Virtual_particle" , even if a virtual particle were to become real the process would still obey conservation of energy.

While potentially true, new universes produced out of quantum fluctuations don't need to have any energy: in the Hamiltonian formalism, a closed FRW universe has energy identically equal to zero.

I should have clarified that the sum total of energy in the universe remains the same no matter what.

This is patently false. Just consider the case of a radiation-dominated universe. In a radiation-dominated universe, if the universe expands by a factor of two, then the volume increases by a factor of eight, but the energy density of the photons drops by a factor of 16. So the total energy in the volume is cut in half.

 

[Ryan_m_b]

This is patently false. Just consider the case of a radiation-dominated universe. In a radiation-dominated universe, if the universe expands by a factor of two, then the volume increases by a factor of eight, but the energy density of the photons drops by a factor of 16. So the total energy in the volume is cut in half.

My apologies, I have not heard of this before. Am I not right in saying that because can be neither created nor destroyed the universe as an isolated system has a constant amount of energy inside of it?

 

[Tanelorn]

Ryan, by spontaneous I meant an instantaneous random quantum fluctuation at the Planck level which created everything. I may be well out of date though, I am pretty retro (1980s) :)

 

[Chalnoth]

My apologies, I have not heard of this before. Am I not right in saying that because can be neither created nor destroyed the universe as an isolated system has a constant amount of energy inside of it?

The problem is that there is no unique definition of total energy in a volume in General Relativity. Since there is no unique definition of total energy in a volume, it can't be a conserved quantity.

Now, you can come up with definitions of energy within General Relativity that are conserved under certain conditions, but there can't be any general conservation law.

Another way of pointing out this fact is to look at where conservation laws come from in the first place: by Noether's theorem, we know that conservation laws reflect symmetries of the underlying laws of physics. Energy conservation, for example, stems from certain properties of the system being invariant with respect to time. In particular, if the metric changes over time, then energy probably isn't going to be conserved. And in the case of an expanding universe, the metric changes over time.

Anyway, you may like reading this essay on the subject:
http://www.desy.de/user/projects/Physics/Relativity/GR/energy_gr.html

One other comment I'd like to make is that there is an absolute conservation law in General Relativity: the stress-energy tensor is absolutely conserved. This includes energy density, but also other things as well. In flat space-time, conservation of the stress-energy tensor reduces to the continuity equation: that the change in energy at a point is equal to the energy flowing into/out of that point. So in the right limit, you do get energy conservation. It just can't be taken to happen globally in a curved space-time.

 

[Tanelorn]

From post 25:

Ben, one other point in that link you provided. I am havng a hard time visualising how most of the stars will eventually be ejected from old eliptical galaxies.

I am still unable to figure out why this happens. Can anyone offer a reason?