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Science Section => Science General Discussion => Physics & Cosmology => Topic started by: Unbeliever on August 13, 2019, 04:56:37 PM

I'm wondering what the exceptionally weak gravitational fields at the centers of the cosmic voids does to time. I've read that time in the voids "moves" or "flows" faster than time in the galaxy clusters, and that in those locations the universe is actually older than it is where the gravitational fields are stronger. This might mean that space is expanding faster in the voids, causing the voids to grow larger, which may drive universal expansion. There is a gravitational gradient, and therefore a temporal gradient, between the more and less dense regions, causing the less dense regions to expand faster than the denser regions. This may have something to do with why they're having such a hard time pinning down the Hubble parameter. It might be that the Hubble parameter is not a constant, but varies with location with respect to voids and clusters.
Here is some background on the voids:
https://www.youtube.com/watch?v=BuO532QnAfw&t=1s
Here is a map of the nearest voids and galaxy clusters:
https://www.youtube.com/watch?v=n92M3gSIYP4&t=321s
Apparently, the voids get bigger, and I would expect the growth rate to increase as the voids grow. The largest voids would grow more quickly than smaller ones.
Of course, this is all just speculation, but it's fun to think about. Does the universal expansion cause the voids to grow larger, or do the growing voids cause the universal expansion?

It might be that the Hubble parameter is not a constant, but varies with location...
Possibly, but two teams working independently in the late 90's confirmed that the Hubble Constant is not constant over time. They measured the received power of type 1a supernovae (which explode at a known power) to measure vast distances more accurately than possible before. To their surprise, they determined that the rate of acceleration is increasing. Particle physicists think it may be vacuum energy  the more space, the more vacuum energy, which explains the acceleration.

Observational cosmology over a billion years of observation to get the empirical data ... is HARD science.

Possibly, but two teams working independently in the late 90's confirmed that the Hubble Constant is not constant over time. They measured the received power of type 1a supernovae (which explode at a known power) to measure vast distances more accurately than possible before. To their surprise, they determined that the rate of acceleration is increasing. Particle physicists think it may be vacuum energy  the more space, the more vacuum energy, which explains the acceleration.
No one's quite sure just what is causing the accelerated expansion. They call it "dark energy" because they don't know what else to call it. But they don't really understand the mechanism of what's driving it.

No one's quite sure just what is causing the accelerated expansion. They call it "dark energy" because they don't know what else to call it. But they don't really understand the mechanism of what's driving it.
You're right. The main culprit is Einstein's field equations. Now in any differential equation, when you integrate you end up with an arbitrary constant if the boundary conditions are unknown. And so that's what you get with the Einstein field equations, an arbitrary constant. It's energy density because those equations are about energy density. Other than that, those equations give no clue as to what is that energy, how it functions, what are the limits or any other features that would help us to understand. So it's dark, as in obscure...;)

It seems to me that as the voids grow larger, their growthrate would increase as well, which could explain the accelerated expansion. The difference in time flow between the clusters and voids may be miniscule, but over the lifetime of the universe could have added up to a significant amount of elapsed time difference since the big bang.

It seems to me that as the voids grow larger, their growthrate would increase as well, which could explain the accelerated expansion. The difference in time flow between the clusters and voids may be miniscule, but over the lifetime of the universe could have added up to a significant amount of elapsed time difference since the big bang.
Here's a good writeup on the accelerating expansion and why many particle physicists think it's vacuum energy. The problem is we don't have a good measurement of vacuum energy. Right now QFT doesn't make a prediction for vacuum energy density, and attempts to estimate it extrapolating from QFT result in an estimate 120 orders of magnitude greater than what observations in astrophysics suggest.
http://math.ucr.edu/home/baez/vacuum.html

Here's a good writeup on the accelerating expansion and why many particle physicists think it's vacuum energy. The problem is we don't have a good measurement of vacuum energy. Right now QFT doesn't make a prediction for vacuum energy density, and attempts to estimate it extrapolating from QFT result in an estimate 120 orders of magnitude greater than what observations in astrophysics suggest.
http://math.ucr.edu/home/baez/vacuum.html
Yes. I have read Dr Baez too. Without a good quantum gravity theory, we know nothing about this vacuum shit. Theoretical physicists will continue to speculate (I prefer Carlo Ravelli), and experimental physics will remain frustrated.
https://www.youtube.com/watch?v=AumrYDQIuEc
If we don't know what time is, then we really don't know much at all.

Without a good quantum gravity theory, we know nothing about this vacuum shit.
Quantum gravity theory is overrated...

Quantum gravity theory is overrated...
Pythagorean panaceas usually are. Pythagoras already had the answer ... "one".

Pythagorean panaceas usually are. Pythagoras already had the answer ... "one".
Well, TOE is an interesting fantasy. But some people are rude when you debunk...

Well, TOE is an interesting fantasy. But some people are rude when you debunk...
If the first guy got the right answer, then what point do the successors have?

If the first guy got the right answer, then what point do the successors have?
A prime number?

A prime number?
What is more prime than "one"? Pythagoras knew "two" and "three" also.

One isn't a prime number, though it is the loneliest number.

One isn't a prime number, though it is the loneliest number.
Numerical bigot!

Numerical bigot!
Two can be as bad as one, it's the loneliest number since the number one.

Two can be as bad as one, it's the loneliest number since the number one.
Shit, I didn't realize Three Dog Night sang that. It totally ruins Shambala for me ಠ_ಠ

What is more prime than "one"? Pythagoras knew "two" and "three" also.
Pytharogas was obsessed with triangles...

Pytharogas was obsessed with triangles...
And squares. He would have liked you.

Pytharogas was obsessed with triangles...
Didn't he prove "The sum of the square roots of any two sides of an isosceles triangle is equal to the square root of the remaining side."? Or maybe that was someone else.

Didn't he prove "The sum of the square roots of any two sides of an isosceles triangle is equal to the square root of the remaining side."? Or maybe that was someone else.
Right angle. He was Republican ;)

Right angle. He was Republican ;)
Do you have to politicize everything?

Do you have to politicize everything?
If it isn't politics, it isn't about power, and if not power, it is irrelevant.
"Power is not a means, it is an end. One does not establish a dictatorship in order to safeguard a revolution; one makes the revolution in order to establish the dictatorship."  George Orwell (1984)

Right angle. He was Republican ;)
That sounds about right  Republicans being illiterate of math. The statement is still incorrect when changing from an isosceles to a right triangle. It seems as if the diploma Oz gave to the Scarecrow came from Trump University.

That sounds about right  Republicans being illiterate of math. The statement is still incorrect when changing from an isosceles to a right triangle. It seems as if the diploma Oz gave to the Scarecrow came from Trump University.
"right" makes up a joke unique to English. Doesn't exist in other languages. A very old prejudice ... as in "right handed" ... at a time that considered "left handed" to be demonic.

If it isn't politics, it isn't about power, and if not power, it is irrelevant.
"Power is not a means, it is an end. One does not establish a dictatorship in order to safeguard a revolution; one makes the revolution in order to establish the dictatorship."  George Orwell (1984)
Whatever happened to love makes the world go round???

Whatever happened to love makes the world go round???
Yoko Ono wouldn't let the rest of the world fuck John.

Yoko Ono wouldn't let the rest of the world fuck John.
Paul is still riling about it.

Whatever happened to love makes the world go round???
I think angular momentum makes the world go round...
:P

It seems to me that as the voids grow larger, their growthrate would increase as well, which could explain the accelerated expansion. The difference in time flow between the clusters and voids may be miniscule, but over the lifetime of the universe could have added up to a significant amount of elapsed time difference since the big bang.
I expect that Einstein will be proven wrong with the spacetime analogy. I probably won't be here when it happens, but there will be a day when rational observation of the universe makes sense again.