# Possible matter being Created/Destroyed?

"To my knowledge gravity easily dominates and the expansion is completely negated..."
IOf you man at a distance of about 4 ly, I'd agree any 'expansion' is immeasureably tiny.

Look at it this way

By your stated logic, cosmic expansion should come to a stop?

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Samuel:
does the intense gravity destroy anything being sucked in?

as already discussed, yes......I came across a description of two theoretical ways this might happen..
Quotes are from BLACK HOLES AND TIME WARPS by Kip Thorne. [This is a great book without any math and really gets into a lot of detail about black holes.] [pg 473-475]

..When a black hole is created by an idealized spherical imploding star....Oppehheimer and Synder showed us..... when nearing a singularity everything experiences an infinitely growing radial stretch and transverse squeeze....and thereby gets destroyed

This means 'tidal gravity' destroys everything as a singularity is approached.

...Belinsky, Khalatnikove and Lifgarbagez [BKL] showed random deformations in real stars will completely change the holes interior...the above description is 'unstable against small perturbations'....[the BKL solution is stable] and the BKL singularity is somewhat like a taffy pulling machine...it stretches and squeezes first in this direction, then that, then another,and yet another. The stretch and squeeze oscillate with time in a random and chaotic manner as measured by an infalling observer...this is a chaotically oscillating singularity.....When the black hole is newborn, its interior tidal forces exhibit violent,chaotic BKL type oscillations. As the hole ages ...they gradually disappear....[and a tidal gravity explanation dominates]....

Samuel posts:

Matter is a type of energy but in a more compact state (I'm not Sure if I'm correct).

Doesn't look like anyone commented..so I will. That's probably an untestable comment....compact relative to what? I like the concept and if it helps you interpret things great.

Matter does have a lot of energy as Einstein showed us [from E = mc2].
With nuclear reactions [fission and fusion] we can access a few percent of that energy. With chemical reactions, which don't affect the nucleus, even less.
I'm not positive, but I think matter-antimatter collisions produce the most energy...100% of the mass becomes energy....but that doesn't mean such mass has any more energy density or is more 'compact' than other mass...just that we can get more out....

This is a really advanced concept: "One could think of a
particle [mass] as a localized concentration of zero-point energy which gravitates and resists acceleration ... no traditional "mass" needed." [Zero point energy is the inherent energy in a vacuum...fluctuations of ground state [lowest energy but not zero] conditions due to their wavelike nature.]

I checked ENERGY DENSITY here
http://en.wikipedia.org/wiki/Energy_density
and did not find anything of great interest...but they list Planck energy density as biggest,
then antimatter..then uranium....take a quick look at the charts if interested....

Under Planck Density I found this:
....This is a unit which is very large, about equivalent to 1023 solar masses squeezed into the space of a single atomic nucleus. At one unit of Planck time after the Big Bang, the mass density of the universe is thought to have been approximately one unit of Planck density....

So we probably won't be using THAT for a while!!!!

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Drakkith
Staff Emeritus
"To my knowledge gravity easily dominates and the expansion is completely negated..."
IOf you man at a distance of about 4 ly, I'd agree any 'expansion' is immeasureably tiny.

Yes, I mean at distances less than multi-megaparsecs.

By your stated logic, cosmic expansion should come to a stop?

Only where objects are held together strongly enough by gravitation and the other forces.

Yes, I mean at distances less than multi-megaparsecs.

Only where objects are held together strongly enough by gravitation and the other forces.

The point is that cosmic expansion itself does not stop. Space itself is everywhere expanding, even here on earth. But as the earth is bumped slightly father away from the sun due to cosmic expansion, it does not have the velocity to sustain a higher orbit, so it returns to its original distance from the sun. Shrink this bumping/returning process to an infinitesimal moment in time, and you see that the earth never really moves outside its regular orbit. So it's not that the distance between the earth and the sun is increasing due to cosmic expansion, but the amount is so small to be negligible. Rather, the distance between the earth and the sun is not increasing due to cosmic expansion, despite space itself expanding around the earth. It's like the tablecloth being pulled from underneath the cups without upsetting them.

phinds
Gold Member
2021 Award
The point is that cosmic expansion itself does not stop. Space itself is everywhere expanding, even here on earth. But as the earth is bumped slightly father away from the sun due to cosmic expansion, it does not have the velocity to sustain a higher orbit, so it returns to its original distance from the sun. Shrink this bumping/returning process to an infinitesimal moment in time, and you see that the earth never really moves outside its regular orbit. So it's not that the distance between the earth and the sun is increasing due to cosmic expansion, but the amount is so small to be negligible. Rather, the distance between the earth and the sun is not increasing due to cosmic expansion, despite space itself expanding around the earth. It's like the tablecloth being pulled from underneath the cups without upsetting them.

Are you sure about this? It has been my belief that "dark energy" EXISTS locally, but has absolutely no effect at all. Not "negligible", but ZERO.

Drakkith
Staff Emeritus
The point is that cosmic expansion itself does not stop. Space itself is everywhere expanding, even here on earth. But as the earth is bumped slightly father away from the sun due to cosmic expansion, it does not have the velocity to sustain a higher orbit, so it returns to its original distance from the sun. Shrink this bumping/returning process to an infinitesimal moment in time, and you see that the earth never really moves outside its regular orbit. So it's not that the distance between the earth and the sun is increasing due to cosmic expansion, but the amount is so small to be negligible. Rather, the distance between the earth and the sun is not increasing due to cosmic expansion, despite space itself expanding around the earth. It's like the tablecloth being pulled from underneath the cups without upsetting them.

I'm not sure I see how this is any different than what I explained. The Earth isn't moving away from the Sun at all. Whether expansion simply doesn't happen, at all, within our solar system, or whether it takes place but is negligible and overpowered by gravity is beyond my ability to answer.

My understanding was that distances between objects in gravitationally-bound systems such as galaxies and solar systems are not increasing.
But they are increasing and we know this because of red shift. As galaxies move farther away from each other they appear to look redder in color.

Drakkith posts:
I'm not sure I see how this is any different than what I explained.

but it is different and that's what I already posted.

chrisbaird captured what I meant in one short statement:

The point is that cosmic expansion itself does not stop.

The fact that gravitationally bound local systems may not move is not the measure of expanding space. Another way to think of it is that over billions of years, if nothing else changed, space would continue to expand but gravitationally bound local systems would not.

phinds
Gold Member
2021 Award
But they are increasing and we know this because of red shift. As galaxies move farther away from each other they appear to look redder in color.

You completely misunderstand. Try to get a grasp on "gravitationally bound systems" such as local clusters of galaxies.

Galaxies OUTSIDE gravitationally bound systems behave as you believe, but not ones inside which is what the statement was about.

Ich
Drakkith said:
Whether expansion simply doesn't happen, at all, within our solar system, or whether it takes place but is negligible and overpowered by gravity is beyond my ability to answer.
This is a purely philosophical point. Expansion in itself has no effect at all on local dynamics. The only thing you notice are the gravitational effects of local matter and energy (including DE). In an ideally homogeneous universe, these are proportional to $\ddot a / a$, the acceleration (or deceleration) of the expansion.

Drakkith
Staff Emeritus
Couple of questions here.

1. If the distance between 2 objects is not increasing, due to normal gravitation, can you consider spacetime to be expanding between those objects?

2. Does the force of expansion cause the orbits of bound objects to be very slightly larger than they would be without expansion by opposing the forces holding them together?

phinds
Gold Member
2021 Award
Couple of questions here.

1. If the distance between 2 objects is not increasing, due to normal gravitation, can you consider spacetime to be expanding between those objects?
I don't see how you could, since it isn't

2. Does the force of expansion cause the orbits of bound objects to be very slightly larger than they would be without expansion by opposing the forces holding them together?

I don't see how that could be since if it DID happen, it would continue to increase, would it not, and then we would have evidence of it (and likely a lot of bad consequences). I mean, why would you assume that once expansion had an effect, it would just STOP having an effect?

Ich
1. If the distance between 2 objects is not increasing, due to normal gravitation, can you consider spacetime to be expanding between those objects?
Spacetime is never expanding. Space is expanding, and therefore "expansion" is just as coordinate dependent as "space". Wich means: you can consider space expanding there or not, it makes no difference.
2. Does the force of expansion cause the orbits of bound objects to be very slightly larger than they would be without expansion by opposing the forces holding them together?
There is no force of expansion.

Drakkith
Staff Emeritus
Well, now I'm very confused again.

Ich
Why?

To be sure, I disagree with

phinds said:
I don't see how that could be since if it DID happen, it would continue to increase, would it not, and then we would have evidence of it (and likely a lot of bad consequences). I mean, why would you assume that once expansion had an effect, it would just STOP having an effect?
(wrong)
Naty1 said:
The fact that gravitationally bound local systems may not move is not the measure of expanding space. Another way to think of it is that over billions of years, if nothing else changed, space would continue to expand but gravitationally bound local systems would not.
(correct, but then: nothing is a measure of expanding space, except the things that are moving away from each other. If they aren't, well, what's the point of talking about expanding space?)
chrisbaird said:
But as the earth is bumped slightly father away from the sun due to cosmic expansion, it does not have the velocity to sustain a higher orbit, so it returns to its original distance from the sun.
(wrong)

Drakkith
Staff Emeritus
Why?

Because this is a confusing topic. :yuck:

Ich
Fair enough.

Greetings Drakkith:

I am also a little confused, perhaps I can dispel it.

The universe is expanding, this is shown by red-shift. No one can measure this directly because the instrumentality would be directly effected. Example if one tried using a ruler to measure the expansion of space the result would be nothing, being that the ruler would be "expanded" as well. This is due to the ruler being in space and being part of space.

The rate of expansion would be effected by gravitation, planets, star systems, clusters, galaxies, galaxy clusters, and so on; as well as any effects of dark-energy and dark-mater. The change of distance between Sol and Alpha Centari would increase because because of the expansion of space-time, but because of the local effects of the Milkyway's supermassive blackhole, the combined gravitational effects of the stars as well as the gravitational effects of the halo of dark matter around the galaxy, would make such expansion possibly unreadable or very small.

The effects of such an expansion, if it is accelerating as current data suggests, all matter will eventually become unstable and decay into low energy photons spread across a cold universe. Matter would not have been destroyed only converted into energy, but so diffuse that it could never be used. This would be in the very very very distant future.

No one can measure this directly because the instrumentality would be directly effected. Example if one tried using a ruler to measure the expansion of space the result would be nothing, being that the ruler would be "expanded" as well. This is due to the ruler being in space and being part of space.

Eimacman, this is incorrect. The space in between galaxies is growing, the objects within space are not.

Greetings Mark M:

Could you explain why an object would not be effected by the expansion of space-time, neglecting the local effects of gravitation?

Greetings Mark M:

Could you explain why an object would not be effected by the expansion of space-time, neglecting the local effects of gravitation?

Eimacman, the expansion of space has absolutely no effect on an objects size. If it did, we wouldn't see any expansion - galaxies would simply grow with the expanding space.

George Jones
Staff Emeritus
Gold Member
Greetings Mark M:

Could you explain why an object would not be effected by the expansion of space-time, neglecting the local effects of gravitation?

For an expansion on what Mark M said, see

http://arxiv.org/abs/gr-qc/0508052.

Sorry, i'm new comer, how to posting ???

phinds
Gold Member
2021 Award
This is a purely philosophical point. Expansion in itself has no effect at all on local dynamics.

I don't understand how this is a philosophical point. Either the expansion of the universe DOES have an effect on local scales or it DOES NOT have an effect. I see absolutely NOTHING about that that is philosophical.

Now, as to whether it MATTERS, I could agree that that's as much philosophical as factual since as I now understand it, if it DOES have an effect, it is negligible and will remain negligible in the solar system for the life of the sun.

Whether or not the effect would (if it exists) be negligible at a galactic scale I do not understand.