Why is space accelerating?

[JocktheMotie]

A hydrogen cloud sometimes collapses to become a star. There must be sufficient pressure, density, and heat obtained to initiate fusion of hydrogen nuclei to form helium nuclei. The energy formed in process of fusion is essentially a consequence of gravitational collapse.

The gravatational collapse is a reversion from the high energy potential resulting from the big bang, essentially to a lower energy potential as matter returns locally to singularity.

A. All energy formed in process of fusion is a consequence of gravitational collapse.
B. Gravitational collapse is a reversion from the high energy potential resulting from the big bang as matter attempts to return locally to singularity.
C. Will there be a gravitational repayment on the huge investment in outward momentum at the big bang?

It's fun to think about, like pulling on a rubber band.

Great, but unrelated to my question. Please tell me the mechanism that would force space to collapse back into singularity. And how to explain your assumption of the inevitability of the big crunch when the universe is expanding and showing no signs of said crunching.

 

[sLiPpY]

Great, but unrelated to my question. Please tell me the mechanism that would force space to collapse back into singularity. And how to explain your assumption of the inevitability of the big crunch when the universe is expanding and showing no signs of said crunching.

New Proof Unknown "Structures" Tug at Our Universe

The expanding universe seems to be clumping up, at the edge of a multiversic toilet bowl?

Seems reasonable to me if something expands, something else must contract.

How all of it fits together I don't know? We still need a more reasonable theory of quantum gravity. Especially when the classical concepts tend to fall apart in certain scenarios.

Just seems more natural for me to wonder about how the singularity occurred in the first place. Thinking if it happened once, it surely can...will and does evenutally happen again.

 

[JocktheMotie]

New Proof Unknown "Structures" Tug at Our Universe

The expanding universe seems to be clumping up, at the edge of a multiversic toilet bowl?

Seems reasonable to me if something expands, something else must contract.

This article essentially says matter on the edge of the observable universe is being tugged outward by matter outside the observable universe.

Which suggests perpetual expansion. Never collapse.

 

[Moiety]

He means that "space" as an entity, is not accelerating because there's nothing its motion is able to be compared against. Its expansion is. He was mostly referring to the accuracy of the thread title, I assume.

Well by the same token couldn't one say space cannot be expanding since expansion, just as acceleration, needs a "frame of reference"?

If there is nothing outside of space how can it be expanding? Or is space viewed as finite these days?

 

[sLiPpY]

This article essentially says matter on the edge of the observable universe is being tugged outward by matter outside the observable universe.

Which suggests perpetual expansion. Never collapse.

There's a little problem with the concept of perpetual expansion.

Where's the energy going to come from?

 

[JocktheMotie]

Well by the same token couldn't one say space cannot be expanding since expansion, just as acceleration, needs a "frame of reference"?

If there is nothing outside of space how can it be expanding? Or is space viewed as finite these days?

Space expands in reference to any point in the universe. It can be said to be expanding because it stretches light, and "volume" of space increases by a certain metric.

With regards to the finite or infinite view of space, I'm actually not sure about that one! I forgot what they finally settled upon. I think it's generally treated as finite, because it's dynamic. If it were static, then infinite. I think.

 

[JocktheMotie]

There's a little problem with the concept of perpetual expansion.

Where's the energy going to come from?

Dark Energy.

 

[Shimmy]

What is extraordinary is that the universe is accelerating away from us at such a rate that eventually the whole universe, except our Milky Way held together by gravity, will pass beyond our event horizon and so become invisible.

So in the future there will be no evidence the Big Bang ever existed.

So it is only in this special time of the universe that we can know where we came from and where we are going.

How does that work? The universe most certainly isn't accelerating faster then the speed of light, therefore the event horizon will just move with along. Granted, other galaxies will become increasingly difficult to see, but then it's just a matter of building more accurate measuring devices.

 

[sLiPpY]

Dark Energy.

Yes, that's current popular thought. Independent from it's actual nature, dark energy would need to have a strong negative pressure to explain the observed acceleration. Which leads some to consider novel ideas such as the "Big Rip."

Dark flow has been speculated about for quite some time, in possibly supporting continued expansion of the universe via external structures. Which I take is your point.

I tend to more so favor cyclic models. Pointing out the only thing we know for sure at this point, is that unlike Einstein and everyone originally thought. The universe is not finite, however I don't believe that it is infinate either.

 

[erm]

Technically "space accelerating" is more accurate, as the "universe's expansion accelerating" is more ambiguous, though both are ambiguous terms.

As it is, the space between any two separate points in the universe is growing, and its growth is accelerating.

A simple image is, if the big bang is the centre of a sphere, its radius time passed, then the surface is the space of the universe at that time.

As far as I am aware, no one really has a clue why this is happening.

Dark Energy.

Dark energy is just another name for unexplained energy. Not a very satisfactory answer to most questions.

On that note, dark matter is just a term for unexplained gravity (or a force behaving similar to gravity).

 

[JocktheMotie]

Dark energy is just another name for unexplained energy. Not a very satisfactory answer to most questions.

On that note, dark matter is just a term for unexplained gravity (or a force behaving similar to gravity).

I actually agree with you here, but this is based on nothing but philosophical bias, not anything concrete. I'm just reiterating accepted explanations, as far as I know. Personally, Dark matter/energy are just fancy accounting tricks to make up for a lack of understanding.

 

[JocktheMotie]

How does that work? The universe most certainly isn't accelerating faster then the speed of light, therefore the event horizon will just move with along. Granted, other galaxies will become increasingly difficult to see, but then it's just a matter of building more accurate measuring devices.

Our current mechanics allow that spacetime can expand faster than light.

 

[erm]

but this is based on nothing but philosophical bias, not anything concrete.

It's a philosophical point, granted.

But for what it's worth, I can't think of anyone who thinks we've explained something if we can't predict it or say what has caused/is causing it. As is the case with these "dark" things.

 

[sLiPpY]

Well, there certainly does seem to be a lot of "magic poop" floating around the universe.

 

[Saslou]

Thanks for all the responses which i have read with delight.
Now i just have to get my head around it all.

 

[Mole]

What's interesting is that no matter where you stand in the universe, the Big Bang appears to start from there.

So every point in the universe appears to be the centre of the universe.

Of course this is counter-intuitive because we can intuitively understand things our own size but things that are very much smaller than us can only be understood with Quantum Mechanics, and things very much bigger than us can only be understood with General Relativity.

So if anyone tells you they understand the atom or the universe, you know they don't.

 

[INTP]

maybe the space isnt accelerating, but we are sucked into some really large black hole type of thing that just makes it seem like space is accelerating