BBT,SLT Order Vs disorder

  • #1
Hi all,
I've been confused lately by the appearance that the universe is becoming more orderly and the second law of thermodynamics that states that all systems start from order and become disordered.
I assume that the Big Bang was hot and disorderly and that it started to get orderly after it the universe started to cool down. According to theory as it cool down elementary particles formed then the elementary particles combined to form atoms and then molecules, etc. It appears to me that as time passes the universe progresses from a chaotic state to an orderly state. Assuming that man survives and evolves he'll manipulate the universe to achieve a more complex one.

Supposedly entropy(disorder) increases as time passes but as I see it the universe started in a state of disorder. Also if entropy increases how can a disorderly system produce something like the human brain, one of the most complex organs in nature?

Can someone please explain this order, disorder contradiction.
 

Answers and Replies

  • #2
I don't know a whole lot on the subject but I'll give my $.02 anyways...

The singularity in which everything started would be purely orderly, I think. Everything is contained into a single, nice and tidy point of existence, where nothing leaves and nothing comes in. I'd imagine that such a singularity would be the ultimate form of order.

As it expanded, although the matter cooled and particles formed, the heat spreading out still created more disorder.

And as for organisms, that one is a bit tricky. Life is a very high form of order, however it causes much more disorder to be created outside of itself. For example reading a book increases the level of order inside your brain, but the heat released by your body decreases the state of order of the rest of the universe by a far more massive amount.
 
  • #3
Chalnoth
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Hi all,
I've been confused lately by the appearance that the universe is becoming more orderly and the second law of thermodynamics that states that all systems start from order and become disordered.
The short answer is that the second law of thermodynamics gets a lot more complicated when gravity is thrown into the mix.

Unfortunately, without a quantum theory of gravity, our ability to express the gravitational degrees of freedom are very limited. There are only a few special cases where we can do the calculations at all. But a couple of them are relevant here. One is a black hole. Another is an empty universe.

One thing that we do know is that if you have a universe that has some amount of mass in it, then the highest-entropy configuration of that universe is for all of the mass to be collected in a black hole. Knowing this, it makes perfect sense that a universe with matter in it gets lumpier and lumpier as time goes on. Eventually there will be nothing but black holes.

We also know that if you have a universe with just a black hole in it, and nothing else, that the entropy of the universe increases as the black hole evaporates. So the eventual fate of the universe, a perfectly empty universe, also makes sense, as it is higher entropy still than a universe populated by black holes.

I assume that the Big Bang was hot and disorderly and that it started to get orderly after it the universe started to cool down.
Actually, the early universe was extremely orderly. Basically, our early universe was all at about the same temperature. Normally, this would be a disordered state. But in this case it isn't, for a simple reason: according to the classical big bang theory, different parts of the universe, despite being at nearly the exact same temperature, have never been in contact.

Cosmic inflation seems to solve this particular problem, because it proposes a different expansion rate in the past which puts all of the visible universe in contact at some point in the past. But it still needs to start with a region that is itself nearly the same density (the only difference is that inflation reduces the size of the region that has to be uniform to be much less than the size of a proton).

Finally, let me say that we don't yet have the whole story where the entropy is concerned for the early universe. But our current, very limited understanding of entropy and gravity makes sense.
 
  • #4
Chronos
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The human brain is very disorderly, see the history channel for details.
 
  • #5
I don't know a whole lot on the subject but I'll give my $.02 anyways...

The singularity in which everything started would be purely orderly, I think. Everything is contained into a single, nice and tidy point of existence, where nothing leaves and nothing comes in. I'd imagine that such a singularity would be the ultimate form of order.

As it expanded, although the matter cooled and particles formed, the heat spreading out still created more disorder.

And as for organisms, that one is a bit tricky. Life is a very high form of order, however it causes much more disorder to be created outside of itself. For example reading a book increases the level of order inside your brain, but the heat released by your body decreases the state of order of the rest of the universe by a far more massive amount.

The fact that all physical laws breakdown in a singularity proves disorder to the nth degree. Organization (order) increases as the universe expands and cools. It appears to me that the BB initially was too energetic for any organization and slowly organized into progressively more complex systems. To claim that the universe organizing matter is increasing disorder just doesnt make since to me.
 
  • #6
The human brain is very disorderly, see the history channel for details.

There's a difference between disorderly conduct vs the organization of the organ we call the brain. Man's history may be at times orderly and at times disorderly and even though the events we experience may seem chaotic there's an order to the chaos.
 
  • #7
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Galaxies, stars, planets etc. are objects with relativly high order (low entropy) but they are only very small fraction of the universe and don't represent the whole entropy of the universe.
The singularity in which everything started was very orderly. Think of it like it was a granade wich explodes and becomes small pieces. Its entropy becames very big. And the decrease of the temperature of the universe is due to its expansion, not because it loses its heat giving it somewhere else. The universe is closed system actualy. This is how I think about it and I may be wrong...
 
  • #8
Galaxies, stars, planets etc. are objects with relativly high order (low entropy) but they are only very small fraction of the universe and don't represent the whole entropy of the universe.
The singularity in which everything started was very orderly. Think of it like it was a granade wich explodes and becomes small pieces. Its entropy becames very big. And the decrease of the temperature of the universe is due to its expansion, not because it loses its heat giving it somewhere else. The universe is closed system actualy. This is how I think about it and I may be wrong...

If we use the grenade analogy then the fragments should be able to organize themselves into human beings...hm I dont think so.
 
  • #9
Perhaps the Universe is like a strange loop. It's entropy is increasing and decreasing at the same time depending how you look at it, something akin to Escher's paradoxical paintings.
 
  • #10
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If we use the grenade analogy then the fragments should be able to organize themselves into human beings...hm I dont think so.

The Big Bang of course wasn't explosion in the sense of grenade explosion so you shouldn't take it too seriously saying that the fragments should be able to organize themselves into human beings... But even though I think we can use this analogy to show that in such system the entropy can increase.

P.s . I'm sorry for my bad english.
 
  • #11
Chalnoth
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The fact that all physical laws breakdown in a singularity proves disorder to the nth degree.
Uh, no, not even close on this one.

Nobody expects the singularity to be real, just an artifact of our incomplete understanding of the early universe. So using it to make any point is just nonsensical.

Perhaps the Universe is like a strange loop. It's entropy is increasing and decreasing at the same time depending how you look at it, something akin to Escher's paradoxical paintings.
Nope. The second law of thermodynamics is inviolable on large scales. Entropy never decreases in the universe as a whole. It's just that the behavior of gravity makes the precise definition of entropy much more complicated than in classical thermodynamics.
 
  • #12
Uh, no, not even close on this one.

Nobody expects the singularity to be real, just an artifact of our incomplete understanding of the early universe. So using it to make any point is just nonsensical.


Nope. The second law of thermodynamics is inviolable on large scales. Entropy never decreases in the universe as a whole. It's just that the behavior of gravity makes the precise definition of entropy much more complicated than in classical thermodynamics.

We use math to explain the Universe so when the math breaks down when we approach a singularity tells me that either our math is not good or the physical laws do break down. You mentioned in a previous post that the universe will eventually become a bunch of black holes as proof of entropy increasing but aren't black holes singularities? Does that make singularities a manifestation of extreme entropy? You also mentioned that black holes eventually evaporate creating a uniformed universe filled with whatever the black holes emitted. That uniformity tells me that suddenly the universe decreased in entropy. That reminds of the Zen like yin-yang that Buddhists talk about.
 
  • #13
The Big Bang of course wasn't explosion in the sense of grenade explosion so you shouldn't take it too seriously saying that the fragments should be able to organize themselves into human beings... But even though I think we can use this analogy to show that in such system the entropy can increase.

P.s . I'm sorry for my bad english.

The point I'm trying to make is that order and disorder are constantly at work intertwined. I can see order increasing and I can see disorder increasing depending how I look at something. Look at us as human beings. We are initially organized into complicated biological entities(entropy decreasing) and then experience aging, illness and finally death(entropy increasing). A dance of order and disorder. I see the universe the same way, a cosmic dance of birth and death.
 
  • #14
Chalnoth
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We use math to explain the Universe so when the math breaks down when we approach a singularity tells me that either our math is not good or the physical laws do break down.
In this case, the math is wrong. We know it's wrong because quantum gravity has to come into effect before you reach Planck-scale densities, while the standard big bang theory uses plain General Relativity.

You mentioned in a previous post that the universe will eventually become a bunch of black holes as proof of entropy increasing but aren't black holes singularities?
Once again, the singularities only exist as a result of General Relativity, which we know is wrong for densities higher than the Planck density. There is no reason to believe any actual singularities exist.

Does that make singularities a manifestation of extreme entropy?
The entropy in this case has nothing whatsoever to do with what is going on inside the black hole. In fact, our calculations would be highly suspect if it did, because we know that General Relativity must be giving the wrong answer for what goes on somewhere inside th black hole. Instead, the entropy only depends upon the area of the event horizon. The Schwarzschild radius of a stellar-mass black hole is around 3km, while that for the supermassive black hole at the center of our galaxy is around 13 million km.

Similarly, a universe that is expanding and dominated by something that acts like vacuum energy, as happened during cosmic inflation, also has an event horizon. This event horizon is categorically different form a black hole horizon, nevertheless it acts similarly in that anything which passes this event horizon can never again communicate, provided the expansion keeps on going.

During inflation, the event horizon was smaller than the size of a proton. With such a smaller area compared to the areas of the event horizons of today's black holes, the entropy was vastly, vastly smaller.

You also mentioned that black holes eventually evaporate creating a uniformed universe filled with whatever the black holes emitted.
Well, no, it makes for an empty universe. What the black holes emit is radiation, which gets redshifted away to nothingness. And if there is a small but positive cosmological constant, the event horizon due to the expansion gets even larger after the black hole evaporates, leading to an overall increase in entropy.
 
  • #15
In this case, the math is wrong. We know it's wrong because quantum gravity has to come into effect before you reach Planck-scale densities, while the standard big bang theory uses plain General Relativity.


Once again, the singularities only exist as a result of General Relativity, which we know is wrong for densities higher than the Planck density. There is no reason to believe any actual singularities exist.


The entropy in this case has nothing whatsoever to do with what is going on inside the black hole. In fact, our calculations would be highly suspect if it did, because we know that General Relativity must be giving the wrong answer for what goes on somewhere inside th black hole. Instead, the entropy only depends upon the area of the event horizon. The Schwarzschild radius of a stellar-mass black hole is around 3km, while that for the supermassive black hole at the center of our galaxy is around 13 million km.

Similarly, a universe that is expanding and dominated by something that acts like vacuum energy, as happened during cosmic inflation, also has an event horizon. This event horizon is categorically different form a black hole horizon, nevertheless it acts similarly in that anything which passes this event horizon can never again communicate, provided the expansion keeps on going.

During inflation, the event horizon was smaller than the size of a proton. With such a smaller area compared to the areas of the event horizons of today's black holes, the entropy was vastly, vastly smaller.


Well, no, it makes for an empty universe. What the black holes emit is radiation, which gets redshifted away to nothingness. And if there is a small but positive cosmological constant, the event horizon due to the expansion gets even larger after the black hole evaporates, leading to an overall increase in entropy.

Can an empty universe really exist If there's no observer? How about dark energy,dark matter, time, do they all cease?
 
  • #16
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Chalnoth said, "Nobody expects the singularity to be real, just an artifact of our incomplete understanding of the early universe."

I have not seen this stated before, can you provide a source for this? I really thought that the singularity part was standard LCDM.
 
  • #17
Chalnoth
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Can an empty universe really exist If there's no observer? How about dark energy,dark matter, time, do they all cease?
Why would an observer make a difference?

Anyway, dark matter eventually decays/annihilates. Time continues. Dark energy is likely to continue on, unless there is a tunneling event where the universe tunnels to a new vacuum with lower energy (this is likely to happen in one location then spread, destroying everything as it goes).

Chalnoth said, "Nobody expects the singularity to be real, just an artifact of our incomplete understanding of the early universe."

I have not seen this stated before, can you provide a source for this? I really thought that the singularity part was standard LCDM.
Ah, found a fairly decent source:
http://www.olduniverse.com/1,5%20Singularities.pdf [Broken]

It includes a relevant quote from Einstein on the subject:
"Theoretical doubts [concerning the creation of the universe] are based on the fact that [at the] beginning of the expansion, the metric becomes singular and the density becomes infinite. . . In reality, space will probably be of a uniform character, and the present [relativity] theory will be valid only as a limiting case. . . One may not therefore assume the validity of the equations for very high density of field and of matter, and one may not conclude that the 'beginning of the expansion' must mean a singularity in the mathematical sense. All we have to realize is that the equations may not be continued over such regions."

I don't particularly like how the article puts Einstein's opinions on a pedestal here, but it is an accurate representation of current opinion on the matter, as near as I can tell.
 
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  • #18
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Thanks Chalnoth, this is quite a revelation for me, I had assumed that singularities and black holes were now mainstream facts, even having experimental measurements. Perhaps black holes could still exist which are also not singularities? Perhaps some other structure of matter prevents them shrinking further from a white dwarf to a complete singularity, but which is still smaller than the schwarzschild radius?

It appears that this "olduniverse.com" site seems to be non mainstream to say the least? So I hope the above still applies.
 
  • #19
Chalnoth
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Thanks Chalnoth, this is quite a revelation for me, I had assumed that singularities and black holes were now mainstream facts, even having experimental measurements. Perhaps black holes could still exist which are also not singularities? Perhaps some other structure of matter prevents them shrinking further from a white dwarf to a complete singularity, but which is still smaller than the schwarzschild radius?

It appears that this "olduniverse.com" site seems to be non mainstream to say the least? So I hope the above still applies.
Well, I haven't looked at the site at all. I was just googling around a bit, and thought that paper was reasonable. I definitely was suspicious at the time that it might not be a very good website it was posted on. This happens all too often in cosmology. Putting Einstein's opinions on a pedestal is also a bit of a red flag. It is the theory that is important, not the man. People putting too much emphasis on particular scientists' opinions is generally a red flag that they're not doing good science.

Anyway, you can verify that this mode of thought is very common by googling, "General Relativity predicts its own demise," as this oft-repeated phrase is used in the way I described: singularities in General Relativity are held up as a reason to think that General Relativity must be an incomplete theory.
 
  • #20
Chronos
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Most scientists believe singularities are mathematical 'glitches' in theory. Using time lapse photgraphy, we could run a human being backwards in time and also arrive at a theoretical singularity. It works well until we get back to the fertilized egg cell. The theory then falls apart.
 
  • #21
Most scientists believe singularities are mathematical 'glitches' in theory. Using time lapse photgraphy, we could run a human being backwards in time and also arrive at a theoretical singularity. It works well until we get back to the fertilized egg cell. The theory then falls apart.

I wonder If there's male and female universes giving birth to other universes. Each universe is either male or female. Our universe perhaps being a female giving birth to other universes. After all the universe is "expanding" and once it gives birth it "contracts". Just kidding.
 

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