Would the collapsing of a universe provide enough energy for a Big Bang?

[iMaGiNaTioN]

I just had this random idea and I know nothing about physics, so I would like some of the smart people here to explain this to me. To my knowledge, we don't know how the Big Bang happened. What if the Big Bang happened because the universe collapsed? Is it possible the universe keeps recycling itself? It grows and grows, then begins to collapse eventually, then the energy from the collapse results in another birth of a new universe?? Doesn't something like this happen when stars collapse?? Someone please help me out. Thanks!

[sol invictus]

Many people over the last century have had that idea. It doesn't work very well, because we have no idea how to pass through the point of very high density between the two phases.

You can find some discussion of modern (but not very successful) versions here http://en.wikipedia.org/wiki/Cyclic_model .

[KingMerv00]

I just had this random idea and I know nothing about physics, so I would like some of the smart people here to explain this to me. To my knowledge, we don't know how the Big Bang happened. What if the Big Bang happened because the universe collapsed? Is it possible the universe keeps recycling itself? It grows and grows, then begins to collapse eventually, then the energy from the collapse results in another birth of a new universe?? Doesn't something like this happen when stars collapse?? Someone please help me out. Thanks!

Many people over the last century have had that idea. It doesn't work very well, because we have no idea how to pass through the point of very high density between the two phases.

You can find some discussion of modern (but not very successful) versions here http://en.wikipedia.org/wiki/Cyclic_model .

Also, the evidence doesn't currently support the cyclic model. The universe is expanding at an accelerating rate. If it were going to collapse again, we'd expect it to be slowing.

[scratchy]

If my knowledge as an interested layman isnt outdated, i think most evidence at hand do not support a future collapse of the universe. Instead it seems like its going to keep on expanding as far in to the future as can be calculated.

If on the other hand the universe would collapse, would the mass energy be enough for a new round? Im fairly certain that science have no idea at the moment. If observations would have shown a decreasing expansion instead of an accelerating one, i think it would be a reasonable hypothesis though.

[iMaGiNaTioN]

Thanks for the responses. I should have pointed out that I am aware that the universe is expanding; my question was more in a theoretical sense. What if it did collapse? So scientists really don't know what might happen then? I find that interesting.

I understand that the universe is expanding faster and faster, is it possible for it to begin to slow down? At what speed is the universe expanding?

I do apoligize for my lack of even a basic understanding of many of these principles, but I must ask this (most likely) elementary question: can matter be destroyed? I ask because I have several followup questions to this.

[Cainkane1]

I just had this random idea and I know nothing about physics, so I would like some of the smart people here to explain this to me. To my knowledge, we don't know how the Big Bang happened. What if the Big Bang happened because the universe collapsed? Is it possible the universe keeps recycling itself? It grows and grows, then begins to collapse eventually, then the energy from the collapse results in another birth of a new universe?? Doesn't something like this happen when stars collapse?? Someone please help me out. Thanks!
I was watching Universe and they described the end of the universe as a big rip. The expanding universe would eventually rip apart even on a subatomic scale. Energy and matter would cease to exist. This is supposed to happen 50 billion years from now. Then the scientists explained that the stuff left over may or may not fall into an "envelope" whatever that is and become anothe universe that has a completely different make up and laws of physics. Could our universe come from an event like that?

[KingMerv00]

Thanks for the responses. I should have pointed out that I am aware that the universe is expanding; my question was more in a theoretical sense. What if it did collapse?

I can't help you there.

I understand that the universe is expanding faster and faster, is it possible for it to begin to slow down?

Possible? I guess. There is no reason to think it will though.

At what speed is the universe expanding?

According to wiki (http://en.wikipedia.org/wiki/Hubble%27s_law), 74.2 ± 3.6 (km/s)/Mpc. In other words, a galaxy that is one Megaparsec away is retreating at about 74.2 km/s.

[MervinFerd]

Also, the evidence doesn't currently support the cyclic model. The universe is expanding at an accelerating rate. If it were going to collapse again, we'd expect it to be slowing.


There's a really big pin floating in space somewhere outside the current edge.

When it hits that pin, POP!

[Klimax]

I do apoligize for my lack of even a basic understanding of many of these principles, but I must ask this (most likely) elementary question: can matter be destroyed? I ask because I have several followup questions to this.

Converted to energy:yes (annihilation)
Otherwise I don't think so.

[Ocelot]

How much energy do you think a new universe requires? Would you be suprised to hear that the negative gravitational potential energy in thue universe could potentially offsets the positive energy soted as mass, kinetic and heat energy meaning that the net amount of energy in the universe couple potentially be zero?

A tricker problem with a cyclic universe would be entropy. Not least because entropy is a trickier concept at the best of times.

[iMaGiNaTioN]

What is causing the universe to expand? Is it dark matter or energy? I know one theory (as mentioned above) is that everything in the universe will become ripped apart. The space between planets, galaxies, etc is constantly growing. If all matter in the universe was ripped apart, would that stop the universe from expanding, or speed that expansion up?

[LordoftheLeftHand]

What is causing the universe to expand? Is it dark matter or energy?

If you estimate the mass and position of the moon and earth and use newton's (or Einsteins) equations you will get a result for the orbit of the moon that matches what we see. If you do the same thing for a star orbiting a galaxy you will not get the result we observe. To get the results we observe from the equations we have to put in a mass for the galaxy that is many times heavier than our original estimates. One of the possible solutions to this problem is the idea that there is something in galaxy that we can't see but has a lot of mass (and there are many ideas of what this something could be). This unknown something is sometimes referred to as "dark matter" (dark in that we can't see it, matter in that it adds gravatational force).

When scientists tried to measure the rate at which the universe is slowing down they discovered that it is not slowing down but speeding up. That means this morning the universe is expanding faster than it was yesterday morning. Imagine if you pushed a ball down a hallway at 1 meter per second. If you turned your head for a instant to talk to your friend and then looked back and the ball was rolling at 3 meters per second you would assume something gave it an extra push when you were not looking (maybe a cat took a swipe at it as it went past a doorway?). The universe appears to be constantly getting an extra push from an unknown source. This unknown pushing source is sometimes called "dark energy".

[Dorian Gray]

Also, the evidence doesn't currently support the cyclic model. The universe is expanding at an accelerating rate. If it were going to collapse again, we'd expect it to be slowing.isn't that kind of arrogant? it has to happen during our lifetimes or it isn't going to happen?

[edd]

isn't that kind of arrogant? it has to happen during our lifetimes or it isn't going to happen?

I think you're confusing the issue of if the universe is expanding, or if the expansion is accelerating.

If the universe is going to recollapse it's quite reasonable to expect that if the universe is currently expanding, that expansion should be slowing.

It's hard to think up a cosmology that at late times (now) would accelerate but at later times would manage to stop that, decelerate, stop expanding and start to contract.

[sol invictus]

If the universe is going to recollapse it's quite reasonable to expect that if the universe is currently expanding, that expansion should be slowing.

It's hard to think up a cosmology that at late times (now) would accelerate but at later times would manage to stop that, decelerate, stop expanding and start to contract.

It's possible, but it requires something fine-tuned. For example a scalar field like the inflaton, but with a potential energy function that's going to become negative in the future. That would give you something roughly like the opposite of inflation and cause a crunch.

But since we've seen to evidence for that, it has to be hiding pretty effectively.

[iMaGiNaTioN]

If you estimate the mass and position of the moon and earth and use newton's (or Einsteins) equations you will get a result for the orbit of the moon that matches what we see. If you do the same thing for a star orbiting a galaxy you will not get the result we observe. To get the results we observe from the equations we have to put in a mass for the galaxy that is many times heavier than our original estimates. One of the possible solutions to this problem is the idea that there is something in galaxy that we can't see but has a lot of mass (and there are many ideas of what this something could be). This unknown something is sometimes referred to as "dark matter" (dark in that we can't see it, matter in that it adds gravatational force).

When scientists tried to measure the rate at which the universe is slowing down they discovered that it is not slowing down but speeding up. That means this morning the universe is expanding faster than it was yesterday morning. Imagine if you pushed a ball down a hallway at 1 meter per second. If you turned your head for a instant to talk to your friend and then looked back and the ball was rolling at 3 meters per second you would assume something gave it an extra push when you were not looking (maybe a cat took a swipe at it as it went past a doorway?). The universe appears to be constantly getting an extra push from an unknown source. This unknown pushing source is sometimes called "dark energy".


Is there (hypothesized) any way to destroy all the matter and energy in the universe, and have the universe expansion deccelerate? In other words, is all the matter perhaps causing the expansion? I try to envision a universe that is completely void of stars, planets, anything.. it's just empty. Is this what will eventually happen to the universe? If it does, what effect will that emptiness have on the expansion?

[LordoftheLeftHand]

Is there (hypothesized) any way to destroy all the matter and energy in the universe, and have the universe expansion deccelerate? In other words, is all the matter perhaps causing the expansion? I try to envision a universe that is completely void of stars, planets, anything.. it's just empty. Is this what will eventually happen to the universe? If it does, what effect will that emptiness have on the expansion?

I really don't know but the following thought comes to mind (no idea how accurate it is though): How would you know if something completely devoid of anything is expanding? How would you even measure its expansion or contraction?

[Singularitarian]

I just had this random idea and I know nothing about physics, so I would like some of the smart people here to explain this to me. To my knowledge, we don't know how the Big Bang happened. What if the Big Bang happened because the universe collapsed? Is it possible the universe keeps recycling itself? It grows and grows, then begins to collapse eventually, then the energy from the collapse results in another birth of a new universe?? Doesn't something like this happen when stars collapse?? Someone please help me out. Thanks!


Yes it can. Depending on what energy state the universe is in, the universe could literally squeeze itself out of existence upon the collapse, where the energy and matter is sucessfully used for a universe just beginning in its ground state big bang.

So yeh, it is very possible the end and the beginning are more identical than what could possibly be imagined. On a fundamental scale, i have shown before that the past and future existences are indestinguishable, and so much that any future collapse must end in a singularity, just as much as from the beginning it had arose.

[Singularitarian]

Is there (hypothesized) any way to destroy all the matter and energy in the universe, and have the universe expansion deccelerate? In other words, is all the matter perhaps causing the expansion? I try to envision a universe that is completely void of stars, planets, anything.. it's just empty. Is this what will eventually happen to the universe? If it does, what effect will that emptiness have on the expansion?It is within current thought that the vacuum itself is physical, so removing the physical aspect will require the dissapearance of the vacuum altogether.

The General Theory only entertains what is mathematically-called the pure gravity solution, and this solution is a universe which is devoid of matter.Normally, it's considered pointless to assume a matter-less universe because the vacuum is a physical vacuum, and matter is but one part of the big manifold. The devoid nature of solid matter would not dissallow the entire vacuum to have a non-zero amount of energy.

[Singularitarian]

I think you're confusing the issue of if the universe is expanding, or if the expansion is accelerating.

If the universe is going to recollapse it's quite reasonable to expect that if the universe is currently expanding, that expansion should be slowing.

It's hard to think up a cosmology that at late times (now) would accelerate but at later times would manage to stop that, decelerate, stop expanding and start to contract.

Reasonable, maybe, but not the only solution we can deal with. Doctor Michio Kaku believes that the universe is acclerating as a sign of the universe actually using up more energy, readying for a quantum leap, an instantaneous change from state to another. So the expansion of the universe may actually not slow down as a hypothesis for some collapse.

[Singularitarian]

I was watching Universe and they described the end of the universe as a big rip. The expanding universe would eventually rip apart even on a subatomic scale. Energy and matter would cease to exist. This is supposed to happen 50 billion years from now. Then the scientists explained that the stuff left over may or may not fall into an "envelope" whatever that is and become anothe universe that has a completely different make up and laws of physics. Could our universe come from an event like that?

An envelope is just a geometrical structure, in this case, used to represent the possibility of any of the space and time to ''fall off'' into a tiny universe. There maybe many baby universes out there.

[KingMerv00]

isn't that kind of arrogant? it has to happen during our lifetimes or it isn't going to happen?

I don't understand how your objection applies to my statement.

[Dorian Gray]

I think you're confusing the issue of if the universe is expanding, or if the expansion is accelerating.

If the universe is going to recollapse it's quite reasonable to expect that if the universe is currently expanding, that expansion should be slowing.

It's hard to think up a cosmology that at late times (now) would accelerate but at later times would manage to stop that, decelerate, stop expanding and start to contract.Don't ALL explosions accelerate and then stop? Don't exploded stars eventually reform into other stars?

I can't explain it, but this argument sounds to me like the argument against evolution that claims we don't see evolution happening, so it isn't happening. This is happening on an even larger scale than evolution.

[Dorian Gray]

I don't understand how your objection applies to my statement.Sorry. I'm saying that if we can't detect it in the, what, 100 years since we have been able to detect such things, and then say it isn't going to happen, that's very arrogant (not of you personally, but of scientists in general). I mean, are we sure we've detected all the matter there is, and know what's going on in other parts of the universe? How does so-called dark matter affect acceleration or slowing of expansion? What are the viable, peer-reviewed alternate theories? There are several different theories outlined on Wikipedia, for example.

ETA: I guess, to use an analogy, this claim is like sitting on the beach at low tide, watching the water rise for 3 hours, and then concluding that the water will continue to rise forever.