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Author Topic:   Thermodynamics and The Universe
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 1 of 186 (382977)
02-06-2007 2:28 PM


In the recently closed thread, our new member EODoc made some claims regarding the nature of the universe, inspired by consideration of the laws of Thermodynamics. These are oft-repeated claims by the creationist crowd and I would like to propose a thread where we can discuss this.
I open with my reply to EODoc but would encourage others to join in with comments, questions and refutations Big Bang & Comsology of course!
In short, the fact that we exist demonstrates that possibility 1 cannot be true because if the universe is infinitely old then such a state (the heat death) would have already been reached.
Heat death is a state that exists in an open or flat Friedmann ( or closed Lemaitre ) Robertson Walker universe. None of these are universes that have always existed. There are many possibilities for eternally existing universes that do not have thermodynamic problems. Next?
I hope you can see quite clearly that if the universe created itself then we have a little problem called the first law of thermodynamics. Let me know if you need me to expound on what the 1st law is in real terms.
Please do, as I would love to hear your ideas on thermodynamics in a closed universe. First off perhaps you would like to define "energy" as that seems rather important for your 1LoT. And what would happen to your 1LoT as your definition of energy breaks down and becomes fairly meaningless (as all mine do when we get back toward t=0 in a F(L)RW universe)
I hope you can see quite clearly that if the universe created itself then we have a little problem called the first law of thermodynamics
No, on the contrary, the 1LoT has the problems when we enter regions of the universe where naive ideas of energy and heat and such-like make little to no sense.
I don't think you can argue against this except by saying that the laws of thermodynamics don't apply to the universe as a whole but it would be hard to make such an argument based on known science
Thermodynamics applies to systems of multitudes of classical particles. To consider the Universe as a whole is to have one very unclassical particle. How exactly does Thermod even begin to apply?

Replies to this message:
 Message 3 by happy_atheist, posted 02-06-2007 4:02 PM cavediver has replied
 Message 4 by Chiroptera, posted 02-06-2007 4:36 PM cavediver has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 5 of 186 (383200)
02-07-2007 1:12 PM
Reply to: Message 4 by Chiroptera
02-06-2007 4:36 PM


I do find it amusing that people try to apply "physical laws", which are used to describe phenomena within the universe, to the "creation of the universe"
Yep, though scientists have been guilty of this in trying to explain creation ex nihilo in terms of pair-creation and the like!
So even in a classical universe existing for a finite amount of time, there is no violation of the law of conservation of energy: there was no point in time when the energy content of the universe was different.
Nicely put... will use that myself It's easier than trying to explain the breakdown in definition of energy at the t=0 point.
God, what a weird topic. This is going to wear out the quote key on my keyboard.
Yeah, noticed that myself a month or so back, where every fourth word I wrote was in "quotes"... I guess it's that or bring out the heavy maths. You may now appreciate what I meant a while back when I said that very few scientists actually have a real grasp of the Big Bang. All the bits for t > 10e-33s are easy, it's that bit from t=0 that gets you

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Replies to this message:
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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 6 of 186 (383205)
02-07-2007 1:23 PM
Reply to: Message 3 by happy_atheist
02-06-2007 4:02 PM


This was one of the most amazing things I saw when I was studying physics. I hated thermodynamics, but when I took a statistical mechanics course and saw the well known 'laws' drop out from simple quantumn mechanics (ha!) and some approximations that can only be made with extremely large numbers of particles it was quite eye opening.
Funny, I was exactly the same. I still hate traditional TD but stat mech is fascinating.
Seeing this thread again has made me want to go find my physics texts and start learning all over again!
Then my job is done
But it does bring to light how hard it is for a non-physicist to grasp how their every-day point-of-view governed by common sense rules is totally non-applicable to the universe as a whole
Quite. And it's not just the non-physicist. EODoc is a perfect example of a physicist (physical chemist) who is a complete fish-out-of-water when it comes to considering fundemental cosmology - no better and in fact considerably worse than many of the well-informed laymen who frequent EvC. To be fair, my knowledge of chemistry is pretty awful...

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Replies to this message:
 Message 7 by Percy, posted 02-07-2007 2:42 PM cavediver has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 16 of 186 (383376)
02-07-2007 8:04 PM
Reply to: Message 7 by Percy
02-07-2007 2:42 PM


I fear we may have lost EODoc, I haven't seen him since AdminPD closed that other thread.
I fear you're right, which is extremely frustrating as a study of EODoc's thought processes would be infinitely more useful than just keeping a thread on-topic.
How does someone, anyone, reach the PhD level without passing association with so much knowledge as to force the realization of how little one knows
I'm still shocked and appalled over this, and simply can't understand how he can take his position. I have met bio-chem graduate creationists before, but I never imagined one could get to post-doc. I'd be very very interested to learn at what stage he became a creationist.

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 19 of 186 (383430)
02-08-2007 4:44 AM
Reply to: Message 13 by Buzsaw
02-07-2007 6:55 PM


Buz, you should know better... this is a science thread.
Your idea of god requires the physical space and time dimensions of the universe to exist. Mine does not. Therefore, my idea of god >> your idea of god How's that?
Essentially you are assuming that the entire energy of the universe popped into existence suddenly from nothing
No, it is not assumming it comes from nothing. You cannot "come" from "nothing". If you are talking simply about energy, I'll use the standard reply that the energy of universe is zero. The positive energy of the mass is offset by the negative energy of the expansion. Happy now?
The only other alternative is that the Universe is infinite without beginning or end as we claim for the intelligent designer, the source of all existing energy.
Who's this "we"? And what do you mean by energy?

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Replies to this message:
 Message 20 by happy_atheist, posted 02-08-2007 5:20 AM cavediver has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 22 of 186 (383435)
02-08-2007 5:55 AM
Reply to: Message 20 by happy_atheist
02-08-2007 5:20 AM


I assume that this is an approximation that applies only to macroscopic systems? If so, does this approximation break down as one approches a singularity? Is 'Energy' of any use at that point?
That's the idea, yes. The word "energy" is bandied around as if everyone is clear of its meaning. But it is very misunderstood - it has no clear unambiguous definition in most types of universe, even at macroscopic scales. At the level of the very early universe, it's not a term we even use.

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 23 of 186 (383437)
02-08-2007 6:06 AM
Reply to: Message 17 by NosyNed
02-07-2007 8:12 PM


Re: Light stretching
The point is that a recession velocity of "c" doesn't mean very much. We use it as the defintion of the Hubble Sphere, but that's about it. There is nothing special about "c" when comparing two different frames in a curved space-time. The particle horizon is the sort of equivalent of the horizon created by a particle receding at c in SR - where we get the infinite red-shift - but it occurs in expanding universes at recession velocities greater than c.

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 24 of 186 (383439)
02-08-2007 6:17 AM
Reply to: Message 8 by SplifChief
02-07-2007 4:09 PM


Hi SplitChief, welcome to EvC
The basics have already been dealt with but I'll just re-iterate them:
Think of expansion of the universe not as movement of the superclusters, but that of the empty space in-between stretching. Apart from a little lcoal wiggling, nothing actually moves as the universe expands. The good old balloon analogy perfectly demonstrates this - dots drawn on the balloon do not move but get prgressively further apart as the balloon inflates.
There is no limit to the rate of this expansion and this is not a problem becasue nothing is actually moving.
The question of how big is the observable universe is a bit odd though, because I have have to ask "when?" The superclusters we observe are now much much further away than they were when the light we see left them. So do we mean - how far were they away when they looked like we see them? - or how far are they away right now when they may be totally different?.
Right now, the observable universe has a radius of about 46 billion light years. That means that something that a photon emitted from us not long after the BB is now 46 billion light years away, despite only travelling for 13.5 billion years. So on top of its 1 light year for every year from its own speed of light, it got a free ride of 32.5 billion light years from the expasnion of the universe!

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 25 of 186 (383440)
02-08-2007 6:20 AM
Reply to: Message 9 by kuresu
02-07-2007 4:22 PM


again, not sure if this is the right answer, but...
No, it's not But read the other replies and you should get the idea...

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 38 of 186 (383639)
02-08-2007 5:48 PM
Reply to: Message 27 by Fabric
02-08-2007 10:48 AM


Re: just thinking out loud
just a thought
Good one though This is part of the idea behind the Hartle-Hawking No-Boundary Proposal. Our 3 space + 1 time dimensional universe evolves out of a 4 space dimensional pre-universe. This removes the singularity and any concept of "beginning".
In a more general sense, this is entirely reasonable. The 3+1 structure of the universe does not seem fundemental but a hgher-level addition. We also consider space-time with two time and two space dimensions!

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Replies to this message:
 Message 39 by New Cat's Eye, posted 02-08-2007 6:44 PM cavediver has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 40 of 186 (383676)
02-08-2007 7:04 PM
Reply to: Message 39 by New Cat's Eye
02-08-2007 6:44 PM


Re: just thinking out loud
Is there a simple model/analogy for it?
What? For a universe with two space dimensions and two time dimensions? Yeah, right...
I take it this is your revenge, as I will be trying to come up with one all night!

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 51 of 186 (384131)
02-10-2007 7:17 AM
Reply to: Message 49 by RAZD
02-09-2007 9:17 PM


Re: t for two?
quote:
It is a wonderful paper. But, be careful, Tegmark does have a philosophical ax to grind here. He is one who has a soft spot for the Anthropic Principle, the cosmological version of Intelligent Design.
As SG has pointed out, complete nonsense Admittedly the AP has a hierarchy of versions, the higher of which are certainly meta-physical... but nothing to do with ID - pantheistic if anything. But the Weak AP, used here, is simple common sense. To quote again from that article
quote:
The idea is that the universe and its constants are so perfectly picked that the universe as a stable enough place to support matter, much less life, is evidence of Divine Creation
is not the AP in any of its forms. That is just classic design argument.
Edited by cavediver, : changed quote style

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 52 of 186 (384132)
02-10-2007 7:30 AM
Reply to: Message 50 by Son Goku
02-10-2007 6:47 AM


Re: t for two?
F-theory
Now that takes me back Simple idea really - just gives you an extra dynamic of compactification from 12D (10+2) down to 10D (9+1)c.f. low energy M-theory in 11D (10+1) down to 10D (9+1)
I think somebody would be going out on a limb if they started talking about life in such a place.
Exactly - when we used to play with it, it was looking at the reflection/transmission at a pseudo-Riemannian/Kleinian boundary (3+1 space time/2+2 space-time for the readers)
Tegmark's overall idea is similar to mine - reality is simply a necessary aspect of logic/mathematics.

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 53 of 186 (384133)
02-10-2007 7:35 AM
Reply to: Message 43 by Son Goku
02-09-2007 10:31 AM


Re: Two times.
The differences are mostly physical rather than conceptual.
You'd still experience time, the way you usually do. That is, you'd have a past and a future in a linear fashion.
Where's this from? It's not something I've ever really considered... is there still a thermodynamic arrow of time?
I forgot to mention, Kleinian space-time also rears up in Humphrey's cosmology! That's part of its pathological behaviour

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 63 of 186 (386028)
02-19-2007 4:24 AM
Reply to: Message 61 by Buzsaw
02-19-2007 12:38 AM


Re: Illogics Of QM Thermodynamics
so they can patent the healing herb as a complex compound and charge big $$ to fill their pockets.
There's some truth in what you say Buz... despite having had a huge City career, and now running my own very successful business, I have never managed to repeat the unbelievable levels of income I used to generate as a physicist. Industry used to fight hand over fist to give us cash... they saw the immense potential in quantum theory, string theory, relativity. I'm immensely jealous of Son Goku, someone still in the field, and I've heard about the size of his pad and the parties he throws there. I'm working a 100 hour week to scrape a tenth of what he has rolling in. Some just wouldn't believe it....

This message is a reply to:
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