Help with entropy, arrow of time & things created from the vacuum

[Jmanm]

Ive read up on these topics and still don't think I really understand, if someone could correct me where needed & answer my Q's.

Arrow of time.

I can't help thinking there still has to be some more fundamental time that always goes one way, otherwise it seems like saying that
things that happened could be undone literally so that they never happened.To me if the one way direction of the past to the
future is nothing more than physical events happening that obey laws of physics, you wouldn't be able to say something like:
'at any given time one would expect the system to be in equilibrium'.

If the arrow of time is a result of entropy increasing does that mean time is really like a block & the future is
set in stone like a spacial dimension? As I understand the future is not determined according to chaos & the UP.

Can someone explain in a simple way why we don't remember the future & only past? I read its about correlations
but don't really get it.


They say its possible for the wind to deposit sand into a sand castle but classical this would be impossible as the wind doesn't have hands & what they mean is actually due to the atoms not having definite positions & a small chance of them all being in that configuration from quantum tunneling.
Is this correct?

Same as a box of gas molecules in equilibrium, I can't see how they all suddenly appear over in a corner lumped together,
they always have energy jostling around but not enough to all clump. If it's quantum tunneling that give rise to
this, well it's a completely different thing.

 

If you drop an egg on floor, can the event actually reverse straight after? even if so unbelievable unlikely. I can't help to think it could only happen if everything in the future reversed & not just an isolated area & time. As the future events depend on the past.


If protons do decay, does this mean in far future no more things can appear from the empty space like brains etc?

How will a brain form out of empty space? Just like magic it appears? or gradual with many failures along the way? Does the brain
then slowly rot like normal matter?


So how does a brain or the big bang get created from the vacuum energy? This seems completely different from something like
an ice cube forming in a glass of water.I can understand the water molecules forming ice, but how does vacuum energy or
quantum fluctuations form physical things? The energy is almost nothing & in a different form to matter.



I don't understand how the universe was considered a low entropy state around shortly after the big band. Since everything
was spread evenly in a volume. It seems to me that its really only when stars start to form that its low entropy compared
to the distant far future. And what they mean by low entropy is just the right conditions straight after time 0.
Like the right gravity, distribution of matter, having inflation, right physical constants etc.

I don't see how our current universe was like finding a slightly melted ice cube in a glass of water & not what you would likely
expect if the laws are truly time symmetric. Perhaps our observable universe is surrounded by an ocean of brains far out?

 

Slightly off topic, I heard a physicist say QM predicts if you pushed on a wall for such a long time you could tunnel through. But can you say such an event is physical impossible still due to the fact no materials could possible last such long time scales.

 

 

thanks

[studiot]

Hello Jmanm,

 

I suggest you are boggling your mind by falling into the classic trap of extrapolating to much and too far from too little data.

 

That is what going from local effects to the ends of time and the universe amounts to.

 

Try to condense your question into one short paragraph and you will get a sensible answer.

[Strange]

 

 

Can someone explain in a simple way why we don't remember the future & only past?

 

I don't think anyone knows. This is closer to philosophy than science.

 

 

 

They say its possible for the wind to deposit sand into a sand castle but classical this would be impossible as the wind doesn't have hands & what they mean is actually due to the atoms not having definite positions & a small chance of them all being in that configuration from quantum tunneling.

Is this correct?

 

Same as a box of gas molecules in equilibrium, I can't see how they all suddenly appear over in a corner lumped together,

they always have energy jostling around but not enough to all clump. If it's quantum tunneling that give rise to

this, well it's a completely different thing.

 

Both of these seem to be just issues of probability, not anything to do with quantum theory. As all the atoms in a box move around at random, there is a small possibility that they all happen to move in the same direction and pile up on one side, momentarily. This is so unlikely, there is no need to worry about it.

 

Similarly, it is possible for a random collection of grains of sand to form a sandcastle. But, again, this is so unlikely that it will never happen.

 

 

 

How will a brain form out of empty space?

 

This sounds even less likely than the other examples. This sounds like the sort of thing that is used as an argument against evolution.

 

 

 

So how does a brain or the big bang get created from the vacuum energy?

 

I don't know that it does.

 

There is some speculation that the big bang could have been triggered from a false vacuum state.

[Airbrush]

"...Can someone explain in a simple way why we don't remember the future & only past? I read its about correlations
but don't really get it."

 

I thought long and hard about this and the best I can tell is because the future didn't happen yet.

 

That question was a piece of cake.

 

"How will a brain form out of empty space?"

 

It doesn't, first a universe of matter must pop out of "empty" space through a big bang. Then that matter rearranges itself over cosmological time, under special circumstances, until you have life, then a brain.

Edited November 16, 2016 by Airbrush

[substitutematerials]

 

How will a brain form out of empty space? Just like magic it appears?

 

I believe the OP is referring to the Boltzmann Brain hypothesis. Sean Carroll describes it well here, although he takes a while to get to the point. The basic gist of it is this: Why did our universe begin with such low entropy? A tempting answer is that our universe is only a tiny patch of a much larger multliverse which is at maximum entropy, and all the order we see is the result of a highly improbable random fluctuation. However if we accept this idea, we must acknowledge that in this larger arena, it is much more likely for a entirely formed and functional brain to pop into existence than for our entire ordered universe to come about, since the single brain doesn't require nearly as low an entropy fluctuation. So the vast majority of consciousnesses are likely to be not the product of natural selection in ordered environments, but disembodied brain that pop into existence only long enough to contemplate their existence and then vanish.

 

This idea is hilarious and alarming and seems to disprove something, although I'm not sure what exactly.

[Jmanm]

Hello Jmanm,

 

I suggest you are boggling your mind by falling into the classic trap of extrapolating to much and too far from too little data.

 

That is what going from local effects to the ends of time and the universe amounts to.

 

Try to condense your question into one short paragraph and you will get a sensible answer.

I don't see the point in these forums if I could get the same type of replies on a PC gaming forum. Judging by the majority of replies on many threads sadly these forums seem to be all about dropping short useless comments. Why are you here?

 

I have read many topics in physics, cosmology & stuff that is speculative & its simply not fully understandable for most laymen. I will never shorten my questions.

 

A sensible answer as you put it will be useless & won't explain or help.

[Mordred]

To be honest your post is kind of random.

Considering the subject matter breaks down to time-reversible symmetry with entropy as the arrow of time.

There are quite frankly time reversible processes but As far as I know entropy isn't fully time reversible. At least not on a global universe scale.

 

The low entropy beginning is quite simple to understand. All particles at the stages are in a state of thermal equilibrium.

 

This state can be described simply via its temperature which correlates to photons. Via the Bose-Einstein statistics the entropy of photons (degrees of freedom) including its anti particle is S=2. As more particles decouple the entropy increases. You can find the sequence here.

 

http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde

http://www.wiese.itp.unibe.ch/lectures/universe.pdf:"Particle Physics of the Early universe" by Uwe-Jens Wiese Thermodynamics, Big bang Nucleosynthesis

The second article in chapter 3 and 4 is better coverage.

One of the details of specifically block is deterministic which amounts to time reversible processes. Though that alone can be a lengthy discussion best left under philosophy.

The thing is you mentioned several different models under one post so its difficult to determine the direction of your question.

 

Here is some of the counter arguments for the Block deterministic view.

 

Overall: a lack of predictability in the real universe

In summary, the future is not determined till it happens

(a) time-dependent equations of state, which can be information driven,

(b) quantum uncertainty, which can be amplified to macro scales,

and also in practice by

© statistics / experimental errors / classical fluctuations,

amplified by

(d) chaotic dynamics /occurrence of catastrophes.

Essentially all realistic models of the universe except for very large scale cosmology are non-deterministic. Sufficient reasons for this are:

(i) coarse-graining by its very nature introduces a statistical element; and (ii) quantum processes occur on the small scale, and can be amplified to macro scales, so there is no deterministic microscopic model from which fully predictive classical macroscopic models can always be derived.

 

You can review these here. Which is the source

 

https://www.google.ca/url?sa=t&source=web&rct=j&url=https://arxiv.org/pdf/gr-qc/0605049&ved=0ahUKEwi3hIuamq_QAhUN5WMKHU-HBnQQFggaMAA&usg=AFQjCNHbifo4qFdaYMpt31beTJ-3cIxzSA

 

Personally I don't find the arrow of time well represented by entropy. The term entropy is often too confused. However thats just me I find it an unimportant debate and just stick to time is a measure of rate of change. Without trying to glorify it beyond that. Which we often see on this forum.

 

Wiki covers this a bit but doesn't explain it well.

 

https://en.m.wikipedia.org/wiki/Entropy_(arrow_of_time)

 

The main detail is whether the universe is time symmetric or time assymmetric.

Edited November 17, 2016 by Mordred

[studiot]

I don't see the point in these forums if I could get the same type of replies on a PC gaming forum. Judging by the majority of replies on many threads sadly these forums seem to be all about dropping short useless comments. Why are you here?

 

I have read many topics in physics, cosmology & stuff that is speculative & its simply not fully understandable for most laymen. I will never shorten my questions.

 

A sensible answer as you put it will be useless & won't explain or help.

 

What a rude response to all those who put their own time and effort into replying to you.

 

Since you are already such an expert that you can dismiss my observation in so cavalier a manner I take it you are aware that we do not even know if the Second Law applies to the universe as a whole or not and why.

 

This conundrum was known to the architects of Thermodynamics and has been pondered and debated in a much more civilized manner than your post for more than a century.

 

There are two issues.

 

1) The Second Law applies to closed systems; we do not know if the universe is closed or not.

 

2) We do not know if the universe is finite or infinite. If it is infinite how can its (already infinite) entropy increase?

[Mordred]

two very key questions well done +1 you have detailed part of the heart of the subject.

Edited November 17, 2016 by Mordred