Big bang in reverse?

[Just_me_Mike]

How do we know that the expansion we see is not just a comsomological giant inhale and exhale? It seems to me that the whole theory is hinged on the fact that we found the universe expanding. However, so does my rib cage when I inhale, but eventually I exhale and it collapses. Can the size of the universe not mask the time factor of how long it expands?
I realize there is a cooling factor as well, can someone explain to me why the cooling aspect supports only an expanding universe, and not an inhale/exhale universe?

Any thoughts?
Thanks...

 

[darkendless]

How do we know that the expansion we see is not just a comsomological giant inhale and exhale? It seems to me that the whole theory is hinged on the fact that we found the universe expanding. However, so does my rib cage when I inhale, but eventually I exhale and it collapses. Can the size of the universe not mask the time factor of how long it expands?
I realize there is a cooling factor as well, can someone explain to me why the cooling aspect supports only an expanding universe, and not an inhale/exhale universe?

Any thoughts?
Thanks...

The inhale you describe is actually what is happening. According to thermodynamics the universe will continue to absorb free energy until none is left, and then implode on itself basically. Sure it won't happen for a few billion years at least, but it will happen Stop stealing all my free energy or we'll all die

 

[silvermoon383]

The amount of energy/matter in the universe is constant, but as the universe expands it's getting spread out more and more. This means the density is dropping, leaving less energy/matter per unit of space. Less energy means less heat.

That's why the universe is cooling as it expands. Air does the same thing (though for a different reason.)

 

[Just_me_Mike]

The amount of energy/matter in the universe is constant, but as the universe expands it's getting spread out more and more. This means the density is dropping, leaving less energy/matter per unit of space. Less energy means less heat.

That's why the universe is cooling as it expands. Air does the same thing (though for a different reason.)

So can we say for certain that the expanding of our universe and the cooling down is not just the effect (and not a constant), but it will reverse and heat back up and become more dense? Only that we can't comprehend that because we know it will be a very long time before that happens?

 

[ManTimeForgot]

We are fairly certain the a Big Crunch is not going to occur because our most recent estimations of the rate of velocity for galaxies (how fast they are moving away from each other) has the universe's expansion accelerating.

This is not to say that a Big Crunch is an impossibility, but rather that the Big Chill and the Big Rip are the more likely contenders.


MTF

 

[Just_me_Mike]

We are fairly certain the a Big Crunch is not going to occur because our most recent estimations of the rate of velocity for galaxies (how fast they are moving away from each other) has the universe's expansion accelerating.
MTF

Not to be a smartbut... Does acceleration conclusively define expansion only? I can inhale and exhale at different rates.

Thank you for the info...

 

[silvermoon383]

In order for the Big Crunch to happen the universe would have to stop expanding and start collapsing in on itself. As far as I know, the only thing we know of that can do that is gravity. As ManTimeForgot mentioned, expansion is happening at a faster rate every moment which means gravity has less and less of an effect on separating galaxies.

Again, as MTF said, there's still the possibility of a Big Crunch, we don't know enough. This is why a good chunk of our time and effort is spent on figuring out just what dark matter and dark energy are cause it looks like they're the key to understanding the structure of the universe and for predicting what will happen.

Oh, and the cooling of the universe is a result of the expansion. The cooling does not cause the expansion.

 

[Just_me_Mike]

Again, as MTF said, there's still the possibility of a Big Crunch, we don't know enough. This is why a good chunk of our time and effort is spent on figuring out just what dark matter and dark energy are cause it looks like they're the key to understanding the structure of the universe and for predicting what will happen.

OK well, I realize it is all theory and not a bad theory at that. Though, aren't we basing the entire theory on the assumption that gravity acts the same everywhere in the universe?

I mean this is what dark matter is all about, assuming gravity acts the same here as it does in other galaxies. We call the missing matter "dark matter" because what we see resembles gravity and what we know about gravity here close to earth. As a result we say it must be matter or dark matter out there that is causing things to act as they are.

Is there anything more concrete than this at this point in time? I'd love to do some more research on it.

Thanks...

 

[logician]

Doesn't it depend on how much dark matter is present, a quantity still unknown?

 

[Breathe]

Am I the only one who finds the idea of a "Big Rip" to be eerie-sounding?

 

[Just_me_Mike]

Doesn't it depend on how much dark matter is present, a quantity still unknown?

Well there is the assumption that over 90% of space is dark matter. But it varies where you look.
This assumption is based off the gravitational effects we see present when we look into the outer space and how light is effected, yet we see no mass near that light, we assume it has to be dark matter.

My suggestion is that this only works if Einstein and others are right that gravity is constant throughout the universe. If they are wrong than it is something alltogether different.

 

[themadhair]

Well there is the assumption that over 90% of space is dark matter.

You seem to have confused dark matter with dark energy.

But it varies where you look.

Source?

This assumption is based off the gravitational effects we see present when we look into the outer space and how light is effected, yet we see no mass near that light, we assume it has to be dark matter.

There is considerably more to it than this. Galactic stability was the first reason for proposing dark matter, and it was gravitational lensing that confirmed it. This is different than dark energy which is what you seem to be in a confuddle over.

My suggestion is that this only works if Einstein and others are right that gravity is constant throughout the universe. If they are wrong than it is something alltogether different.

Can you propose a reason why the laws of physics should differ in different parts of the universe?

 

[Just_me_Mike]

You seem to have confused dark matter with dark energy.

Actually, not confusing them, just representing them wrong. When I say that over 90% is dark matter, I should have rather said that over 90% is both dark matter and dark energy combined (at least that is the theory)

Source?

There is a million sources, just google "amount of dark energy vs dark matter".

There is considerably more to it than this. Galactic stability was the first reason for proposing dark matter, and it was gravitational lensing that confirmed it. This is different than dark energy which is what you seem to be in a confuddle over.

No confuddling that I am aware of, I am merely suggesting that the big bang is based on the assumption that gravity is constant throughout the universe. Although I do thank you for pointing out I clarify the amount of energy vs matter in the first part of your post.

Can you propose a reason why the laws of physics should differ in different parts of the universe?

I wish I could propose a reason worthy of posting it. The fact is I can't. I just know that we are basing a cosmological giant and its essence on assumptions that are loosely based. However when I say loosely, I don't mean to insult, because I agree it makes the most sense right now.

 

[themadhair]

Actually, not confusing them, just representing them wrong. When I say that over 90% is dark matter, I should have rather said that over 90% is both dark matter and dark energy combined (at least that is the theory)

Given that they are very different things why are you combining them? Looks like confusion to me.

No confuddling that I am aware of, I am merely suggesting that the big bang is based on the assumption that gravity is constant throughout the universe.

There is considerable evidence supporting this notion and, to my knowledge, zero against. Is it still an assumption of the current evidence supports it?

I don't mean to insult, because I agree it makes the most sense right now.

It looks to me that you don’t even know yourself what it is you are trying to say.

 

[Just_me_Mike]

Given that they are very different things why are you combining them? Looks like confusion to me.

In the scope of the OT I combined them because they make up according to current theory the rest of the known universe, which according to theory is less than 10%. So I don't see a problem combining them for a generalized explanation of universe capacity.

There is considerable evidence supporting this notion and, to my knowledge, zero against. Is it still an assumption of the current evidence supports it?

The evidnce yes points to this, but the opposite is not really considered that I know of. If the opposite were true we would have to rethink everything.
Example, if gravity is constant we could place an object into outerspace and predict trajectory and so forth, however if we find object that are not where they should be, than we may have a situation where gravity is not constant.

It looks to me that you don’t even know yourself what it is you are trying to say.

Sorry to disappoint you, I am just writing and hoping to learn at the same time.
Thanks for the feedback.

 

[themadhair]

So I don't see a problem combining them for a generalized explanation of universe capacity.

So you combine these two very different things, despite one adding to gravitational collapse and the other adding to gravitational rip in a manner that could not be more opposite, simply because they both have the word ‘dark’ in them? Otherwise there is absolutely no need to do so unless one isn’t really sure what they are talking about.

If the opposite were true we would have to rethink everything.

If the earth were flat we would have to rethink everything. If the electromagnetic force were two different forces we would have to rethink everything. If the planets in the solar system didn’t exist we would have to rethink everything.

If the opposite of X were true, and we had no evidence whatsoever for presuming that, then we would have to rethink everything. Is this even an argument or just an attempt at rhetoric?

Sorry to disappoint you, I am just writing and hoping to learn at the same time.

If you want to learn you could probably try reading up on the topic. As it stands you seem to be trying to make a point while not knowing what it is you are talking about. So why not read up first?

 

[Just_me_Mike]

So you combine these two very different things, despite one adding to gravitational collapse and the other adding to gravitational rip in a manner that could not be more opposite, simply because they both have the word ‘dark’ in them? Otherwise there is absolutely no need to do so unless one isn’t really sure what they are talking about.

You seem to not know what you are talking about now. I never said they are the same thing? Where did I write that? All I presented is that the current theory is that the rest of the known universe (other than matter we can see) is part dark matter and part dark energy.

Please see a reference here

From Cornell University: Curious About Astronomy: What's the difference between dark matter and dark energy?
we don't know if dark matter and dark energy are manifestations of the same dark "thing". We know they both must exist to explain certain phenomena, but we still know very little about their make up so we cannot assume they are linked. For now, we think of them as separate, and we believe the cosmos to be composed of roughly 0.03% heavy elements (anything other than hydrogen and helium), 0.3% neutrinos, 0.5% stars, 4% free hydrogen and helium, 25% dark matter, and 70% dark energy.

They don't seem to have a problem combing them so why should I?

 

[themadhair]

They don't seem to have a problem combing them so why should I?

Because your thread is essentially asking the question of whether we will have a big crunch or a big rip, and those two phenomena contribute to the question in exactly the opposite way. Context is really easy to ignore when you are on unfamiliar territory.

 

[Just_me_Mike]

Because your thread is essentially asking the question of whether we will have a big crunch or a big rip, and those two phenomena contribute to the question in exactly the opposite way. Context is really easy to ignore when you are on unfamiliar territory.

No if you reread the orignal post, I did not suggest such a thing, so at this point you are wasting my time. I suggested that the expansion could be part of an inhale exhale system, and that it won't reach extremes in either way.
that it will expand to a point and then contract to a point and then expand, etc etc...

Thanks...

 

[themadhair]

No if you reread the orignal post, I did not suggest such a thing, so at this point you are wasting my time. I suggested that the expansion could be part of an inhale exhale system, and that it won't reach extremes in either way.
that it will expand to a point and then contract to a point and then expand, etc etc...

Thanks...

As I said, context is an easy thing to ignore when on unfamiliar ground.