In terms of the "big freeze" predicted as the end of the universe....

It may not be the "end".... time may keep going.....

19 minutes ago, julius2 said:

In terms of the "big freeze" predicted as the end of the universe....

It may not be the "end".... time may keep going.....

Is there any credible discussion of time stopping in the heat death scenario?

30 minutes ago, swansont said:

Is there any credible discussion of time stopping in the heat death scenario?

Well ... possibly.
Once maximal entropy is reached, and the universe is essentially at equilibrium, no processes can go forward or backward.
Sure, there will be some small oscillations about the equilibrium state, because of QM, but how would you measure the passage of time ?
( if this wasn't off topic, it would make an interesting discussion )

Edit - I see you fixed that problem. Thanks.

Edited Wednesday at 06:20 PM1 day by MigL

4 minutes ago, MigL said:

Well ... possibly.
Once maximal entropy is reached, and the universe is essentially at equilibrium, no processes can go forward or backward.
Sure, there will be some small oscillations about the equilibrium state, because of QM, but how would you measure the passage of time ?
( if this wasn't off topic, it would make an interesting discussion )

I can see how you couldn’t measure time in that case, but is time dependent on that? Does time pass if there’s nothing around to experience it?

Interesting question.
But keeping in mind that ALL processes would be halted, and QM oscillations could go backwards or forward, there would be absolutely no way to detect the passage of time.
If time is redundant, would it still exist indepenently ?

2 hours ago, MigL said:

Interesting question.
But keeping in mind that ALL processes would be halted, and QM oscillations could go backwards or forward, there would be absolutely no way to detect the passage of time.
If time is redundant, would it still exist indepenently ?

Are quantum oscillations well understood?

If so ,is the nature of quantum oscillations a key to any question as to whether or not "time" might cease to exist and , like Samsung pull down all of "creation" with it and prevent its reemergence in any form at all-copper fastening a certified "death" of everything that was or could be ?

I have read that quantum fluctuations can be visualized collectively as a kind of "foam:.

Is there any structure of any kind to this foam or are we talking about a never ending vista of randomness?

I wasn't thinking of Quantum fluctuations as typically understood, but rather fluctuations around the final equilibrium of the maximal entropy universe.
But you do bring up a good point.
The Quantum fluctuations due to the Uncertainty Principle cannot be ignored as they are a necessity of Quantum systems.
The energy-time uncertainty dictates that their deltas must be greater than , or equal to, h-bar/2.
IOW, 'borrowed' energy for the fluctuation must be re-paid within a specific period of time.
As this is a process that even maximal entropy cannot stop, time IS still needed.

5 hours ago, julius2 said:

In terms of the "big freeze" predicted as the end of the universe....

It may not be the "end".... time may keep going.....

I just don't buy the famous Second Law "Heat Death" scenario which is what I assume you mean by big freeze.

This was originally introduced long before we had even a proper idea of molecules let alone sub atomic particles and quanta.

It requires a continuous distribution of energy, which cannot be achieved with our current table of particles and forces.

3 hours ago, MigL said:

fluctuations around the final equilibrium of the maximal entropy universe.

Unless you're suggesting that growth of the scale factor will decelerate to zero, can there ever be a maximal entropy? (IIRC, AOTBE, entropy grows proportionally to ln a)

Ultimately, matter and energy may become so thinly spread out that particle interactions rarely occur, and each particle tends towards its own isolated little ground-state universe of entropy zero (in its own frame of reference). But then, many if not most of these will be photons which don''t experience time anyway.

As for the leptons, while they are able to oscillate between their various flavours/states, they must still be little clocks ticking away for eternity, aren''t they? Which suggests that time will at least continue somewhere. Even when their nearest neighbours have been accelerated away to such an extent that their light cones no longer intersect.

It all begins to sound a bit Hilbert's Hotelish, but I've yet to see anything paradoxical in an asymptotic approach to zero local entropy density at infinite time/global entropy.

Not sure that 'equilibrium' has any meaning at such infinitessimally low densitities. No collisions: no equilibrium.

It is interesting to know about the "heat death"....... but what will happen to "living things".............

1 hour ago, julius2 said:

It is interesting to know about the "heat death"....... but what will happen to "living things".............

Once protons start decaying at a minimum of 10³⁴ years, I can't imagine any living things to be around ...

16 hours ago, sethoflagos said:

Unless you're suggesting that growth of the scale factor will decelerate to zero, can there ever be a maximal entropy?

Omce our galaxy is the only gravitationally bound system in the observable ( causal ) universe, how would you determine growth of the scale factor ?
No, I've already had second thoughts about the situation in a previous post.
Oscillations between energy levels of fundamental particles ( no decay ) would be governed by the energy/time uncertainty relation, making time an essential factor.

3 hours ago, julius2 said:

It is interesting to know about the "heat death"....... but what will happen to "living things".............

They will suffer an ''absence of heat" death. No more stars (or radioactivity etc.) to keep local temperatures much above absolute zero. Chemistry ceases to be a thing. Or at least chemical reactions grind to a halt. No food; no respiration; no metabolism.

2 hours ago, MigL said:

Omce our galaxy is the only gravitationally bound system in the observable ( causal ) universe, how would you determine growth of the scale factor ?

Periodically launch probes into deep space and carefully watch their red shift? Long term experiment, but what else are you going to do for a googol-year?

20 hours ago, sethoflagos said:

Not sure that 'equilibrium' has any meaning at such infinitessimally low densitities. No collisions: no equilibrium.

Not even clear on how photons can in any sense be real if they never interact. "Particle" seems like a term of convenience for some transfer of energy/momentum, not some timeless thing flying through eternity without a transaction. (I'm also suspicious of oscillating leptons in isolation, but that's because I stupidly (densely?) don't grasp the whole particle-as-ontic thing) "Here there be dragons."

2 hours ago, TheVat said:

"Particle" seems like a term of convenience for some transfer of energy/momentum, not some timeless thing flying through eternity without a transaction

Photons of the CMB have red-shifted from 3500^o to 2.7^o in 1.4x10¹⁰ years.
Once all the stars burn out ( say 10²⁰ years ), how long do you think it will take for any of their emitted photons to red-shift to an energy where they can no longer excite fundamental particles? Another 10¹⁰ years ?
What will they be then ?

At that time, the only source of useable energy might come from proton decay ( assuming it actually happens ).

4 hours ago, TheVat said:

Not even clear on how photons can in any sense be real if they never interact.

The thermodynamics of a 'photon gas' is well established and quite real. Very similar to the thermodynamics of a molecular gas, but slightly different equations: (there is no conservation of photons etc.)

On second thoughts, that's not what you're saying is it. You're referring to that unheard falling tree in a forest malarkey. Never really gone in for that viewpoint. Bit too solipsistic for my taste.

7 hours ago, TheVat said:

Not even clear on how photons can in any sense be real if they never interact.

My understanding is that anything that can be measured is considered real.