Curious About the Universe Expanding

Skeptic Ginger

Nasty Woman
Skeptic Ginger
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Feb 14, 2005
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I'm just curious about peoples' thoughts, I know there is no answer we could test.

Watching the current solar cycle, the magnetic field gets stretched until it snaps back, (reversing the poles I believe).

In my Universe contemplating this morning I wondered if the Universe expansion would speed up until it stretched so far, like elastic, and then begin to snap back.

There is a fabric of space involved, so does said fabric simply keep growing as the Universe expands? Or does it have a limit to how far/much it was stretch?
 
In our current understanding, "fabric of space" is just flowery language in regards to the question of whether space will ever "snap back". The actual determining factor is how much mass/energy is there. Currently, it looks like there isn't going to be any "snapping back".
 
Mojo said:
What is there to be stretched?
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The fabric of space, sometimes referred to as space-time.

If you have an hour and need the basics: NOVA The Fabric of the Cosmos

If you just want some examples, we've recently detected gravitational waves from 2 black holes colliding.

Gravitational Waves
Gravitational waves are ripples in space-time (the fabled “fabric” of the Universe) caused by massive objects moving with extreme accelerations. In outer space that means objects like neutron stars or black holes orbiting around each other at ever increasing rates, or stars that blow themselves up. Explore the links below to learn more about these ephemeral phenomena.
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Black holes are thought to drag the space-time frame.

Frame Dragging
Frame-dragging is an effect on spacetime, predicted by Albert Einstein's general theory of relativity, that is due to non-static stationary distributions of mass–energy. A stationary field is one that is in a steady state, but the masses causing that field may be non-static ⁠— rotating, for instance. More generally, the subject that deals with the effects caused by mass–energy currents is known as gravitoelectromagnetism, which is analogous to the magnetism of classical electromagnetism.
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And then there is gravity which bends space. It has to be bending something.
 
RecoveringYuppy said:
In our current understanding, "fabric of space" is just flowery language in regards to the question of whether space will ever "snap back". The actual determining factor is how much mass/energy is there. Currently, it looks like there isn't going to be any "snapping back".
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But do we know enough about dark energy to say that?

Granted it doesn't look like magnetic fields have anything to do with dark energy so maybe that's a bad analogy.
 
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I should probably leave this to those more knowledgeable than myself, but I think the current state of thinking is that it will not snap back, it will just keep right on expanding, but how dark energy works, and what it even is is still a mystery, so we really don't know.

Probably we need to figure out what dark energy and dark matter are, and how they work exactly, before we can really predict the ultimate fate of the universe. This would also help to improve our understanding of how the universe began.
 
Dark energy is inferred from the observation that the expansion is accelerating. The accelerating expansion is enough on it's own (in our current understanding) to infer that there won't be a snap back.
 
Eventually, the expansion of the universe will smaller rip things apart. First, our galaxy cluster will be ripped apart, then our galaxy will be ripped apart. Then anyone looking at the night sky will see no other stars. But this is far into the future.
 
rjh01 said:
Eventually, the expansion of the universe will smaller rip things apart. First, our galaxy cluster will be ripped apart, then our galaxy will be ripped apart. Then anyone looking at the night sky will see no other stars. But this is far into the future.
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Followed by decay of all particles and the heat death of the universe.

https://en.wikipedia.org/wiki/Heat_death_of_the_universe

10 to the power of 106 years at least.
 
I know what the standard prediction is. I was wondering if anyone had alternative ideas or if anyone had even thought about alternative hypotheses.
 
As the expansion of the universe is accelerating, not slowing, as a cycle of expansion/contraction would require.
 
Skeptic Ginger said:
I know what the standard prediction is. I was wondering if anyone had alternative ideas or if anyone had even thought about alternative hypotheses.
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Oh yes, indeed.

With links and footnotes as at Wikipedia:
Wikipedia said:
Some alternative models challenge the assumptions of the ΛCDM model. Examples of these are modified Newtonian dynamics, entropic gravity, modified gravity, theories of large-scale variations in the matter density of the universe, bimetric gravity, scale invariance of empty space, and decaying dark matter (DDM).[1][2][3][4][5]
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See also Wikipedia's article on Non-standard cosmology, which says:
Wikipedia said:
Research on extensions or modifications to Lambda-CDM, as well as fundamentally different models, is ongoing. Topics investigated include quintessence, Modified Newtonian Dynamics (MOND) and its relativistic generalization TeVeS, and warm dark matter.
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Several of those topics are discussed in
Steven Weinberg. Cosmology. Oxford University Press, 2008.​

This subforum itself houses several ongoing threads devoted to alternative cosmologies and related topics (mostly involving alternatives to general relativity):
Similar threads sometimes show up in the Religion and Philosophy subforum. I don't pay much attention to that subforum, but the currently active thread on imagination, theories, and ...reality might have something to do with cosmology—I really can't tell.
 
Unless our universe runs into the anti-universe.

cf James Blish 'A clash of cymbals' or for our US readers 'The triumph of time'.

I think George Gamow and some other astrophysicists of the 70s and 80s posited that the expansion of the universe would slow, stop and then contract, with everything finally collapsing into a single singularity. The possibility then would be there would be a further big bang (the Big Bounce) with another cycle of expansion and contraction. Thus the answer to what came before this universe can be answered. For the universe to contract would require more mass in the universe than we currently know about.

Fred Hoyle (who literally invented the 'Big Bang' theory - certainly deserving a mention by Sheldon), was a proponent of the now discredited steady state theory of the universe.
 
lionking said:
Well, unless the universe is infinite, which many scientists believe.
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When you say infinite, what dimension are you referring to? As far as I know most scientists think it might be infinite in space. Also some think it's infinite in time. But neither of those things changes the heat death. Infinite in time is actually easier to reconcile with heat death than any finite time.
 
Planigale said:
Fred Hoyle (who literally invented the 'Big Bang' theory - certainly deserving a mention by Sheldon), was a proponent of the now discredited steady state theory of the universe.
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Georges Lemaître proposed the theory. Hoyle provided the name possibly in an attempt to disparage it.
 
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