POLL: A shared existence?

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Actually, according to Stephen Hawking, there can be no time prior to the existence of space (Big Bang) as the two are inexorably linked (space and time that is).

Why is that so? Well let me get a few more physics classes under my belt and I can explain...(hopefully)...

 

Late-Night Thinker is right. Time is another dimension just like space, and they are not independent.

There is a flaw to the "existed always" theory. If the universe has always existed, it should've reached a state of equilibrium and there would be no expansion of the universe. If everything is traceable back to a beginning (Big Bang), then perhaps there was a "beginning".

 

Says who? "Everything has to reach a state of stable equilibrium sooner or later" isn't exactly part of Field Theory - nor of Thermodynamics.

Now, if you could prove that a stable equilibrium state of the universe exists, we could do away with the oscillating solution...

 

Newton's third (I think) law contradicts the idea of everything reaching a state of equilibruim, unless you want to consider the complete cessation of atomic movement as "equilibrium".

And doesn't the idea of there being a prime mover in the universe go back to Aristotle?

 

So you're saying that instability is the natural order of things.

 

Very roughly: according to thermodynamics, most systems are under the influence of
a) contributions that tend to bring it to equilibrium.
b) contributions that tend to expand its entropy.

However a funny statistical mechanics theorem blow away the "system always tends towards greater entropy" punch line. Always fun to learn that kind of stuff.

@LTN: you're into physics studies, man?

 

Simplification: A state of equilibrium is defined via the energy related to this state. A system tends to occupy states with lowest possible equilibrium. It is a local equilibrium if the neighboring states of the system are of higher energy, and it is a global equilibrium, if all reachable states are of higher energy.

If you introduce the concept of equilibrium to the universe you have to define the possible states the universe may occupy altogether with the energy related to each state. You will then have to find the state with lowest possible energy to claim that the universe is heading towards it.

What kind of state could that be? If there's one state with lower energy and the universe is in a state with higher energy right now - where'd the energy go that would be set free during the transition? Simply vanish? But the first fundamental theorem of thermodynamics demands the energy to be conserved. Hm. There are no known boundaries of the universe across which the energy could pass.

The second fundamental theorem of thermodynamics states that an entity called entropy exists that will never decrease in a closed system.

However, that all is not heaven sent but rather a clever deduction according to assumptions including the parity of time under reversal, spontaneous processes and irreversibility etc. etc.
In short: we observe how the universe behaves and build our natural laws (another word for observation) accordingly. The flux of the universe may be reversed at some point in time. Our laws would change as well. We haven't observed it yet, but we are talking rather endless time here.

And Newton's third law: "For every action, there is an equal and opposite reaction." Are you talking about energy conservation here as well, Rallymama?

 

In my opinion the universe has always just been there. There was no 'creation' and there will be no 'end' it's just going to keep existing just like it always has. Sure, new planets will form and old ones will be destroyed. Stars will super-nova and new stars will be born.

Infinity is possibly the most hard concept to grasp. If you kept going in one direction in space for... let's say at the speed of 36000 light years an hour (that's ten light years a second) you wouldn't have even seen a decimal point of a percentage of the universe. There are more galaxies in the universe then there are atoms in our own galaxy (and thats alot of atoms). The sheer size of the universe is boggling, humans struggle to understand that something can just last forever. The moment you think you've got a general idea of how large the universe is, it's at least a million times the size you've just imagined and then some.

 

I knew I should've taken physics at school! At the time it wasn't very interesting, but now I just can't get enough of it! Fascinating!

 

Wasn't symmetrical timeflow disproven? At least for a very exotic particle if I recall correctly (and I may very well be wrong).

 

Careful: nerd talk going on here! Skip it for your own sake!

The main problem is: there isn't a "theory of everything". However, we talk like there was. That's the reason for many misunderstandings. Thermodynamics is fundamentally different from Gravitation or Quantum Field Theory, even if all of them share a common set of vocables and terms.

On a fundamental level we have four forces: gravitation, electro-magnetism, weak and strong interaction. The latter three can be combined - gravitation resists all attempts of further unification up till now.

So we have quantum on one hand and gravitation on the other. One problem of astro physics today is that seperation - we simply cannot predict gravitational behaviour of the universe if we start with mikroskopical assumptions. It is not easy to say: see, elementary particals behave like that, accordingly the universe will fluctuate/collapse/reach a state of equilibrium/whatever.

That said, we can deal with symmetrical variables. There's a theorem from Emmy Noether: each symmetrical variable is connected to a conserved quantity. In classical physics symmetry under time reversal leads to conservation of energy, symmetry under translation leads to conservation of momentum, etc.

On an elementary level we have some additional symmetries we don't perceive in our makroskopical world. We have the so called parity (P) and the charge (C). It was found, that parity, charge, and time were not symmetrical under reversal, however the combination of two simultaneous changes of C and P was. For quite some time. In 1964 the violation of the CP-symmetry was shown by Christenson et al.

As a last resort, we have the CPT-symmetry today, meaning that we can apply without further adaption the same laws that exist in a specific system to a system where charge, parity and time are reversed with regard to the first one at the same time.

So, symmetrical time flow would be possible if charge and parity would be reversed at the same time.

OK, I thought about Rallymama's statement. I think you mean the "third fundamental theorem" of thermodynamics, Nernst's theorem. This theorem states a given sysem cannot be cooled down to zero temperature. Because of quantum.

Now, if you define a "total" equilibrium in which we have zero temperature, then we could say that this equilibrium could never be reached. But zero temperature is not really necessary for an equilibrium. I'm not sure that there is a contradiction.

As a last thought: the scenario universe expanding, expansion slowing down, universe contracting, universe collapsing is depending on the total mass of the universe. Our knowledge today inidicates that we have not enough mass in our universe for this scenario, gravitational forces are simply not strong enough. The most likely future of our universe is an infinite expansion with the decay of all existing particles. But don't you worry. This will happen in something like 10^1000 years.

Over and Out.

 

Thanks for interpreting for me, Darkthrone. It's been a looooooong time since I've studied physics, and while the concepts are in there somewhere the details are hazy.

But to get back to Ik's question... all this talk of physics and models for how the universe works and trying to combine all the different levels of physical observations into one grand Theory Of Everything can't help but reinforce my belief that God exists. Can I PROVE it? No, but I just can't swallow that everything works the way it does, on so many seemingly contradictory levels, just by chance. And not only do the mechanics of this strange universe work, the place is alive! How cool is that?

Thanks, God. Nice job!

 

That Italian chick I spoke with said there now is evidence of CPT violation.
Well, there ought to be a matter/anti-matter asymetry.

Our knowledge today indicates that we have not enough mass in our universe for this scenario, gravitational forces are simply not strong enough.

True. But if its evolution is now dominated by a cosmological constant, the universe may yet stop expanding (according to some models).
[/nerd talk]

I just can't swallow that everything works the way it does, on so many seemingly contradictory levels, just by chance.

This is interesting. I may be totally out of the picture here so don't sue me yet : is it in some way more reassuring to have a 'sentient' god control the universe than relying on pure chance (the definition of which is also debatable btw)?
Would you rather have a sort of humanoid(if I understand right God created mankind in his own image), that is, an entity therefore related to us, in charge than indiscriminate, cold mechanics you can't relate to emotionnaly or personnaly or something?
Is the relationship with God a very personal one?

Just being curious.

 

Reassuring, no; sensible, yes. That's the short answer

As far as God being either sentient, humanoid, related to us, or in charge... well, you said that, not me. I believe in a God who's both the creator and the animator of nature, but who isn't necessarily in charge of it all. If there were something in charge, why would people have free will, and why would evil be allowed into the mix?

A relationship with God is definitely a very personal thing. I haven't entirely sorted things out in my own mind, but I do believe that God exists. I'm going to leave it at that for now while I go away and think some more.

 

@Rallymama

I have been told that God gave us free will so that we could give it back to him. Just try to trust the love...


Back to physics...

Why is the universe expanding at an accelerating rate? My understanding of gravity is that objects follow a straight line through curved spacetime. What appears as gravity to us is in fact an object following a straight line. That being the case...why is spacetime curved in such a way as to cause matter to follow a straight path to mass that seems to us in the opposite direction as all known matter?

edit...

Upon further thought I think I really missed the mark on how the notion of spacetime operates.

Bear in mind that I don't really know what I'm talking about...

[ April 08, 2005, 07:23: Message edited by: Late-Night Thinker ]

 

It’s all rather complicated, I agree. Your Italian friend is most likely talking about the CPT violation in neutral kaon systems. And she is correct, from all that I know.

What we call standard model of particle physics is CPT invariant. It is one of the best tested models in the history of physics, an overwhelming success. However, within the boundaries of the standard model no explanation for gravity is possible because it is a model based on the assumption of a flat space time which respects some other symmetries (locality, unitarity and Lorentz invariance if you must know).

During the last decades there have been attempts to remedy these short comings – with the most notable attempt of the String Theory. Well, we call it String Theory, but in reality it’s a bunch of numerous quantum field theories operating on a highly curved space time (curved space time => gravity). There have been some successes deriving the standard model from string theories, but it is not really my field of work, so I can’t get into details. It seems that String Theories and their extensions and modifications are the most promising way though.

From a theoretical point of view, highly curved space times (of the black-hole type for example) may violate the aforesaid CPT symmetry (e.g in the spontaneous breaking of Lorentz symmetry, or – weird enough – so called “space time foam”, singular fluctuations in quantum gravity that may be interpreted as mini black holes). There are independent types of those violations that occur in some string theories. However, none of these theories is the be all, end all. Many are not satisfying in major respects of our intuitive understanding of the universe (10 dimensions with 6 huddled into a point and all that). That’s why I chose to pass over them. Especially, since we still do not know how to interpret all consequences of CPT violation. Here’s a good (if a bit outdated) article on the subject:

http://physicsweb.org/articles/world/11/12/3/1

The original statement of Tassadar, however, was directed at the equilibrium state of the universe with the notion of this leading to a stable, never changing universe at some point in an incredible far future. This “arrow of time” as a consequence of entropy production is not related to microscopic physics, it is no intrinsic attribute of elementary particles but rather a statistical effect independent of the underlying interactions. Thermodynamics will yield the same results regardless of the microscopic theory currently en vogue. There may be a revolution on the lowest level of our physical understanding of the world; things like entropy will not be touched.

That said, it is not entirely clear what the equilibrium state of the universe is. The universe might never reach equilibrium and produce entropy all the time. If the critical mass of the universe was big enough, the universe would again collapse at some point in time. And because we do not know enough about the time when the universe was “born”, we cannot predict what the physical laws could be like at the moment of the universe’s “death”. A newborn universe out of the ashes of the old one could still be a valid scenario, for all we know. Although it is not likely, like I said before.

Nature (or God if you insist) is close-fisted with its secrets.

@Oxymore: it is possible to have matter/anti-matter asymmetry without CPT violation. You need C and CP violation, thermal non-equilibrium and baryon number violation. Although the sheer number of baryons could still not be explained sufficiently...

 

Maybe a bit off topic, but here goes anyway.

Physics, as I understand it: When takling about the expanding universe, the galaxies aren't moving away from each other, rather space between the is expanding. Like if you mark two spots on a balloon and then fill the balloon, the spots (the galaxies) haven't moved, but the balloon (the universe) has expanded. So the Big Bang didn't occur in a defined place, but everywhere and is still occuring everywhere all the time. Gravitation then pulles stars and galaxies together, forming clusters and overcoming the expansion of the universe.

 

Yikes, string theory...

So Darkthrone... when are you taking over Stephen Hawking's position?

Nice posts, by the way. Very intriguing!