Question reguarding the expanding universe

[Chalnoth]

Once the universe is at a constant percentage rate growth, will everything continue to accelerate forever?

As far as we know, yes. Until there is nothing left in the universe. See here for a good description of the far future to the best of our understanding:
https://en.wikipedia.org/wiki/Future_of_an_expanding_universe

 

[marcus]

Once the universe is at a constant percentage rate growth, will everything continue to accelerate forever?

Yes.
If the growth rate H = a'/a really does level out at a constant then each year a distance will increase by a bit more than it increased last year.

Just like if the bank pays a constant interest rate of, say, 1%, your savings will increase by a bit more than they did the previous year.

 

[Martin0001]

As per so called "cosmological constant", lambda, Einstein himself called it "his biggest blunder".
Now it apears that lambda is real after all.
More interesting thing is that lambda may not be a constant at all, only may grow with progress of time.
This could lead to an interesting end of the world scenario, still two dozens of billions years away at least, where everything disentangles and all components (galaxies, then stellar systems, then stars and planets, then chemical molecules, then atoms, then hadrons, then any gravitational singularities (if exist)) would disentangle and any basic components left (photons, leptons, quarks) would inflate away from each other to infinity, to form some bizarre singularity like phenomenon named Big Rip.
Essentially you would end up with situation where each basic building block of matter is surrounded by a separate, "personal" event horizon, so no interaction would be possible.
In such scenario entropy in any point of space would reach maximum possible value, hence time would end.
Last year some evidence indicating possibility of such an outcome was published.

 

[PeterDonis]

Last year some evidence indicating possibility of such an outcome was published.

Reference, please?

 

[Martin0001]

Reference, please?

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.043532#nf

 

[Chalnoth]

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.043532#nf

That's not evidence. It's a hypothetical model.

 

[Martin0001]

That's not evidence. It's a hypothetical model.

Correct.
I should rather use word "speculation".
Evidence should rely on obsevation.
Nevertheless interesting.

 

[quantumphysics]

Essentially you would end up with situation where each basic building block of matter is surrounded by a separate, "personal" event horizon, so no interaction would be possible.
In such scenario entropy in any point of space would reach maximum possible value, hence time would end.
Last year some evidence indicating possibility of such an outcome was published.

This is extremely interesting.
If such a circumstance actually occurs, then reality itself may actually stop. (Quantum mechanics explanation)
According to the Copenhagen interpretation, there are no properties of reality if nothing is there to "observe" or interact with it.
Fascinating stuff! Thanks for sharing that

 

[marcus]

As per so called "cosmological constant", lambda, Einstein himself called it "his biggest blunder".
Now it apears that lambda is real after all.
More interesting thing is that lambda may not be a constant at all, only may grow with progress of time.
...
... any basic components left (photons, leptons, quarks) would inflate away from each other to infinity, to form some bizarre singularity like phenomenon named Big Rip.
...
Last year some evidence indicating possibility of such an outcome was published.

Reference, please?

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.043532#nf

That's not evidence. It's a hypothetical model.

Correct.
I should rather use word "speculation".
...

Here's the paper involved in this exchange, so we can understand it better if we want:
http://arxiv.org/abs/1409.4918
A New Approach to Cosmological Bulk Viscosity
Marcelo M. Disconzi, Thomas W. Kephart, Robert J. Scherrer
(Submitted on 17 Sep 2014 (v1), last revised 6 Feb 2015 (this version, v2))
We examine the cosmological consequences of an alternative to the standard expression for bulk viscosity, one which was proposed to avoid the propagation of superluminal signals without the necessity of extending the space of variables of the theory. The Friedmann equation is derived for this case, along with an expression for the effective pressure. We find solutions for the evolution of the density of a viscous component, which differs markedly from the case of conventional Eckart theory; our model evolves toward late-time phantom-like behavior with a future singularity. Entropy production is addressed, and some similarities and differences to approaches based on the Mueller-Israel-Stewart theory are discussed.
6 pages. To appear in Physical Review D

 

[Chalnoth]

According to the Copenhagen interpretation, there are no properties of reality if nothing is there to "observe" or interact with it.

We've observed wavefunction collapse without directly observing the wavefunction being collapsed:
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.77.4887

So no, observers definitely aren't required. Collapse occurs as a result of interactions between systems.

 

[Martin0001]

We've observed wavefunction collapse without directly observing the wavefunction being collapsed:
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.77.4887

So no, observers definitely aren't required. Collapse occurs as a result of interactions between systems.

But if you have only a single particle within each event horizon, how any interaction could be possible?

 

[Chalnoth]

But if you have only a single particle within each event horizon, how any interaction could be possible?

Assuming a cosmological constant, there would still be interaction with the Hawking radiation produced by the cosmological horizon.

That probably wouldn't be relevant, though. Such a system would likely be in a pseudo-equilibrium state, where entropy within the horizon is maximized.

 

[PeterDonis]

That probably wouldn't be relevant, though.

It would if you're trying to understand why "interaction" is still occurring even though there is only one "particle" within the horizon.