How Will the Universe End? Big Crunch Theory

[UrbanXrisis]

According to most recent and most believed theories, how is the universe going to end? Of will it just keep expanding? How solid is the theory of the Big Crunch?

thanks

 

[Garth]

How long is a piece of string?
The standard view that if the actual density is above the critical density then the universe will contract at some point has been thrown into some confusion because of the deduced accelerated cosmic expansion and the consequent role of the hypothetical dark energy.

Whether the total density is this large or not depends on who you speak to. So,

how is the universe going to end?

your guess is as good as anybody's!

Garth

 

[Entropy]

how is the universe going to end?

When ever I feel like it.

 

[RAD4921]

Speculation

All theories on how the universe is going to end is pure speculation at this point in man's knowledge of the universe.

Some suggest as you have that the universe may end in a big crunch. Others claim that the universe will expand or exist for an infinite amount of time in which the universe would die of a "heat death".

I lean towards a cyclic universe in which the universe is constantly expanding and contracting. To propose a beginning and end to the universe is born from linear thinking.

 

[setAI]

speculation indeed-

given the new ideas like branes from M-theory and spin-networks from LQG- it could very well be that the evolution of the universe will unfold in ways we cannot even imagine- such as future collisions/intersections/mergings with random branes casuing unpredictible effects- or the matrix of spacetime could deform/transform in time due to the exponential increase in Dark Energy and expansion- who knows?

and this doesn't even consider what role intelligence with technology developed to the limit of physics with zero-point energy and quantum computing may do

 

[UrbanXrisis]

Question: Do we know that the universe will end?
Question: If yes, There's obviouly no way to advoid it. So what's the use of living when in several billion years, we will be a singularity? What is the point to life?
Question: If no, what do YOU think will happen to the universe?
Question: If you answer that you can't say for sure, then which one are you leaning towards?

and this doesn't even consider what role intelligence with technology developed to the limit of physics with zero-point energy and quantum computing may do

explain that more to me? Expecially the "role intelligence"

 

[turbo]

Question: Do we know that the universe will end?

We do not know that. The universe may be in a state of steady creation, for all we know.

Question: If yes, There's obviouly no way to advoid it. So what's the use of living when in several billion years, we will be a singularity? What is the point to life?

Wow! Most of us go through our lives (even doing little things like brushing our teeth and dressing ourselves) with enough commitment to make that a moot question. We can pose the question academically, but the fact that we (and other animals) act in ways that that enhance our self-preservation should be considered proof that life has value (at least to ourselves). Of course, even microbes seem to exhibit "behavior" that is self-serving, so perhaps we cannot blithely attribute value to such behavior - we're just hard-wired that way.

Question: If no, what do YOU think will happen to the universe?

The universe may coast along forever, creating new matter incrementally. It could die a long slow "heat death", or maybe collapse in upon itself. There are a lot of possibilities. Maybe we're here to try to find that out.

Question: If you answer that you can't say for sure, then which one are you leaning towards?

The universe may coast along forever, creating new matter incrementally.

 

[Phobos]

It seems that the current mainstream inclination is that the universe will expand forever and fizzle out (heat death).
See research from:
http://cmb.phys.cwru.edu/boomerang/
Cosmic Background Radiation by Cosmic Background Explorer (COBE)
Wilkinson Microwave Anisotropy Probe (WMAP)

 

[UrbanXrisis]

The universe may coast along forever, creating new matter incrementally.

How is the universe creating new matter? Matter can't be just created can it? I don't see how that is physically possible.

heat death

I read somewhere that Heat death is when the universe reaches maximum entropy. What does that mean exactly? That the disorder in the universe is too high be hold survival? could someone explain this some more?

 

[turbo]

How is the universe creating new matter? Matter can't be just created can it? I don't see how that is physically possible.

Matter can be created through Hawking radiation. The vacuum surrounding black holes is suffused with a sea of virtual particle/antiparticle pairs. Black holes can promote virtual particles of the quantum vacuum to real particles by capturing their partners. If the field of virtual particle pairs can be polarized by the presence of mass, black holes will be able to capture an excess of antimatter particles, thus promoting an excess of matter particles to "real" status. If CERN's Athena project detects a difference in the gravitational infall rate between hydrogen and antihydrogen (which they intend to produce in experimentally usable quantities) the mechanism by which the ZPE field can be polarized will be established.

Warning: This model is not standard cosmology, by any stretch. The Hawking radiation model is quite widely accepted in some circles, but the consequences of Hawking radiation in the presence of a polarized ZPE field have not been examined, to my knowledge.

 

[Phobos]

How is the universe creating new matter? Matter can't be just created can it? I don't see how that is physically possible.

Virtual particles exist but I'm not so sure its "creating" matter like turbo-1 describes. But that's probably best left to a separate topic (check out some of the ongoing/past discussions by turbo-1). The mainstream theory does not point to a steady state universe.

I read somewhere that Heat death is when the universe reaches maximum entropy. What does that mean exactly? That the disorder in the universe is too high be hold survival? could someone explain this some more?

It's not disorder in the sense of the universe running wild. Instead, as entropy increases, energy is converted to less useful forms (e.g., lower and lower heat). Stars will burn out. Matter will fall apart. Black holes will evaporate. The sparse particles that remain will get farther apart with no significant interactions. Everything will have sunk to the lowest energy state.

 

[UrbanXrisis]

Thank you very much for the posts, I still have more questions though.

Matter can be created through Hawking radiation. The vacuum surrounding black holes is suffused with a sea of virtual particle/antiparticle pairs. Black holes can promote virtual particles of the quantum vacuum to real particles by capturing their partners.

So the black hole is actually radiating particles because within the black hole, there are particles being formed from "a sea of virtual particle/antiparticle pairs." How is this radiation able to excape the gavatational pull of the black hole? what do you mean by the word "virtual"?

It's not disorder in the sense of the universe running wild. Instead, as entropy increases, energy is converted to less useful forms (e.g., lower and lower heat). Stars will burn out. Matter will fall apart. Black holes will evaporate. The sparse particles that remain will get farther apart with no significant interactions. Everything will have sunk to the lowest energy state.

How is this different from the theoretical "Big Freeze"?

 

[turbo]

It's not disorder in the sense of the universe running wild. Instead, as entropy increases, energy is converted to less useful forms (e.g., lower and lower heat). Stars will burn out. Matter will fall apart. Black holes will evaporate. The sparse particles that remain will get farther apart with no significant interactions. Everything will have sunk to the lowest energy state.

In regard to the "heat death" model, perhaps its fair to say that everything that exists in our universe is an expression of energy differences. When everything in the universe has died, diffused, and cooled to the point that there are no energy differences left, existence is over. The fact that the universe may not yet be at zero degrees absolute is moot. As you say, the energy has been converted to "less useful forms".

 

[UrbanXrisis]

there are no energy differences left

how can energy be destoryed? Or as you put it, the universe "dies"?

 

[turbo]

So the black hole is actually radiating particles because within the black hole, there are particles being formed from "a sea of virtual particle/antiparticle pairs." How is this radiation able to excape the gavatational pull of the black hole? what do you mean by the word "virtual"?

The vacuum (empty space) of the universe is not really empty, according to quantum theorists. It is a sea of particle/antiparticle pairs that arise spontaneously and annihilate spontaneously within the parameters set by the Heisenberg Uncertainty Principle. The existence of the the quantum vacuum (sometimes referred to as the ZPE field as an acronym for zero point energy) has been experimentally proven by quite a number of experiments that have been designed to demonstrate the Casimir Effect (do a Google search on that!). Steven Hawking has described a method (Hawking radiation) by which one of these particles (which we call "virtual particles" due to their fleeting and normally self-negating existence) can be captured at the event horizon of a black hole. It cannot annihilate its partner, as it would in the "normal" (if we can call it that with a straight face) quantum vacuum, so it becomes a "real" particle, which will persist in our universe. Thus "new" matter is formed in our observable universe.

 

[UrbanXrisis]

The vacuum (empty space) of the universe is not really empty, according to quantum theorists. It is a sea of particle/antiparticle pairs that arise spontaneously and annihilate spontaneously within the parameters set by the Heisenberg Uncertainty Principle. The existence of the the quantum vacuum (sometimes referred to as the ZPE field as an acronym for zero point energy) has been experimentally proven by quite a number of experiments that have been designed to demonstrate the Casimir Effect (do a Google search on that!). Steven Hawking has described a method (Hawking radiation) by which one of these particles (which we call "virtual particles" due to their fleeting and normally self-negating existence) can be captured at the event horizon of a black hole. It cannot annihilate its partner, as it would in the "normal" (if we can call it that with a straight face) quantum vacuum, so it becomes a "real" particle, which will persist in our universe. Thus "new" matter is formed in our observable universe.

does this mean that the black hole loses mass?

 

[turbo]

does this mean that the black hole loses mass?

In Hawking's model, yes the black hole loses mass because it has to give up some energy to promote the particle outside the event horizon to "real" status.

 

[Chronos]

Current physics make steady state theory [continuous creation of new matter] a long shot in the competition for the title of 'Standard Model'. The first law of thermodynamics, which states energy cannot be created or destroyed, is still very popular and experimentally well supported. GR also predicts energy conservation, albeit the case is not ironclad. And energy conservation is also required by Noether's Theorem, as well as the Hamiltonian operator in quantum mechanics.

More telling is the lack of a viable theoretical model for the creation of matter ex nilho. BBT, of course suffers this same problem. The difference is the problem only occurs one time - at the very first instant of the Big Bang - and under extreme conditions where the very laws of physics are poorly understood. Explaining the creation of matter ex nilho after the BB is much more problematic. We have a relatively thorough understanding of the conditions and physical laws that apply after the Big Bang, and there are no experimentally supported theoretical models for creation of matter ex nilho that satisfy these constraints.

Perhaps such a model will someday emerge. At present, it just does not look promising. Do we need to specifically look for such evidence at present? I would say no. If the evidence is out there, it will be found as a natural consequence of our continuing to expand our knowledge of current theory. And that is a generally more productive and practical approach than firing what-if shots into the dark. People who make a career in research are not inclined to take a lot of low percentage shots.

Heat death is just that. All the stars that can be formed will be formed, and will all eventually run out of fuel.

 

[UrbanXrisis]

I read this:

The second possible end is where the universe would continue to expand forever: Everything will eventually disappear, and the temperature of the universe will be absolute zero (0 K, -459.688 °F). This second process has many names, but the most common is the "Big Freeze;" it would happen if the universe does not have enough matter for the collective gravity to counteract the expansion. It would result from the reverse situation of the Big Crunch - there is not enough matter in the universe to halt the expansion.

Is this person talking about heat death? What is the difference between the Big Freeze and Heat Death?

Chronos, you say that the BBT is more popular than the creation of matter ex nilho. What about your input on how the universe will end?

How reliable is Hawking Radiation?

 

[Chronos]

Personal opinion? How awkward. In a big freeze scenario, you pretty much recreate the conditions from which the Big Bang arose [a pervasive state of equilibrium]. In that case, I would guess if it happened once, why not again? Quantum theory suggests nature objects to such a state. Summary, another BB appears likely [perhaps inevitable] after the current universe thins out sufficiently.

 

[Phobos]

how can energy be destoryed? Or as you put it, the universe "dies"?

Not destroyed, but converted to less useful forms/lower energy states. It like when you burn fuel (gasoline, wood, whatever)...a lot of it is converted to heat. Heat dissapates away (cools off) and is tough to recapture & reuse. So, to keep going, you need more fuel. (If you could recapture that heat with 100% efficiency, then you'd have a perpetual motion machine...which is impossible of course.) Eventually the fuel runs out and it's all converted to heat. Heat spreads out across the universe & cools down to lowest levels.

So, the energy that was once "compact" & able to do work is diluted out by space and time.

 

[UrbanXrisis]

In a big freeze scenario, you pretty much recreate the conditions from which the Big Bang arose [a pervasive state of equilibrium].

isnt this the same as heat death?

 

[Chronos]

isnt this the same as heat death?

Yes, the big freeze is synonymous with heat death.

 

[UrbanXrisis]

Which one is more widely believed? Heat death or the Big Cruch?

 

[Chronos]

Big freeze leads the pack right now.

 

[meteor]

According to most recent and most believed theories, how is the universe going to end?

One of the most popular theories is that it will end in a Big Rip, where all matter will be torn apart. A modification to this idea is the theory that will end in the Bigger Rip. Seems more scary even
http://arxiv.org/abs/astro-ph/0405333
Bigger Rip with No Dark Energy

 

[Chronos]

Thanks for the reminder, meteor. The Big Rip thing has received appreciable attention and is certainly an option still on the block. It has a certain appeal compared to the option of a slow heat death. I can't help but wonder if such an end state would set the table for another big bang. Would space-time itself simply collapse back into a singularity?

 

[meteor]

Hi, Chronos. Well, the Big Rip is also known as Big Rip singularity, but I'm not sure if it will lead to another Big Bang. ANyway, it was clear until now taht a universe filled with phantom energy would end inevitably in a Big Rip, until I have seen this paper
http://arxiv.org/abs/astro-ph/0407424
Avoidance of Big Rip In Phantom Cosmology by Gravitational Back Reaction
It says that Gravitational Back Reaction of cosmological perturbations will be an antidote to the Big Rip. It seems like good news

 

[UrbanXrisis]

One of the most popular theories is that it will end in a Big Rip, where all matter will be torn apart.

Does this mean that the universe will expand too fast that it will just rip itself? how is it possible to tear all matter apart?

 

[Garth]

This assumes that the "dark energy" that is invoked to explain the accelerating universe becomes predominant, not only at cosmological scales but atomic ones as well.

According to meteor "It seems like good news", I cannot understand how!

Garth

 

[turbo]

This is assumes that the "dark energy" that is invoked to explain the accelerating universe becomes predominant, not only at cosmological scales but atomic ones as well.

According to meteor "It seems like good news", I cannot understand how!

Garth

I think he was saying that Gravitational Back Reaction (negating the Big Rip) was good news, but since none of us are going to live past the next 100 years or so, much less live out the cosmos, I can't see how it is good or bad news either way. Now if a white dwarf not too far from the Sun managed to accrete enough mass to enter the electron degeneracy stage, or if a large asteroid or comet managed to score a hit on our little planet, we would be toast. As it stands, though, our Sun will go red giant and cook all life on Earth eons before the Big Rip gets a shot at us. In more practical terms, if we don't smarten up, we will probably kill ourselves by imbalancing and poisoning our environment before the cosmos even gets a fair chance to take us out. :uhh:

 

[meteor]

I think he was saying that Gravitational Back Reaction (negating the Big Rip) was good news,

True. The idea of Phantom energy was proposed in this paper
http://arxiv.org/abs/astro-ph/9908168
then later, it was found that Phantom energy would lead to a Big Rip, aka Cosmic doomsday. According to astro-ph/0302506, with a Hubble constant H=70 km/s/Mpc and a dark energy equation of state w=-3/2, this Big Rip will occur in 22 Gyr. That's too bad, but Wu and Yu paper gives new hope to everyone that is fearing the Rip.

I can't see how it is good or bad news either way

We are surely fried anyway, you are true, but it's not good to thow the towel so soon. We as humans have achieved great feats, don't understimate the capability of human intelligence. Who knows what we are capable to do

 

[meteor]

Does this mean that the universe will expand too fast that it will just rip itself? how is it possible to tear all matter apart?

It's because dark energy, contrarily to the ordinary matter that we are used to, exerts negative pressure, that is, tries to separate things, is a kind of antigravity. It would be OK if it would not be the case that Phantom energy is a kind of dark energy that has the property that its energy density increases with time. The matter of the fact then, is that its power is increasing, so there's a moment that it really rips all known structure, that's the Big Rip. In Phantom Cosmology, the end of time will occur in the Big Rip singularity, it will occur 22 Gyr from now with the parameters of my previous post. But some structures will be torn apart a bit before. For example, according to
http://arxiv.org/abs/astro-ph/0302506
with the parameters indicated, the Milky Way will be stripped 60 million years before the Big Rip singularity

Just to dissipate the gloomy tone that my last posts have acquired, I'll say that I'm not very worried about the Big Rip, because phantom energy is not the only candidate to dark energy. Other candidates are the cosmological constant, and a scalar field called quintessence. In these models there's no Big Rip.

 

[UrbanXrisis]

energy density increases with time

How does it increase in energy? Or do we not know that yet. Also, since the universe is accelerating in expansion, is this why theorists have concluded on the existence on this Phantom energy?

 

[meteor]

How does it increase in energy?

Good question. Do you have any idea? Look formula 4 of this paper. It gives the density of phantom energy as a function of time...
http://arxiv.org/abs/astro-ph/0407048