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-   -   A question related to cosmology( or perhaps philosophy) (http://www.physicsforums.com/showthread.php?t=107579)

kant Jan21-06 08:18 PM

A question related to cosmology( or perhaps philosophy)
 
If the universe is expanding/stretching, what is it expanding/stretching into? Is it nothingness? Or rather is it is 'nothingness' only in the sense that we cannot give it a word or a definition?

Where did all the mass-energy in the universe came from? Did it came from nothing? Of course, the last question is absurd.

Since we define the universe as being everything( EX: energy-mass,all the temporal and spatial concepts), then it makes little sense to imagine something 'outside' the universe, or 'before' the big bang. To make such inquiry, to me, is merely a limitation on language itself. There in fact a deeper level of human consciousness or intuition; A feelings/sense/mind s-eye that give us the conviction that there is 'something' out there. Something that our langauge cannot take us.

ray b Jan21-06 10:23 PM

I have named it the NOT YET

we will se if anyone else uses that
or comes up with a better name

kant Jan21-06 10:28 PM

Damn it, my thread is moved again.

kant Jan21-06 10:42 PM

Quote:

Quote by ray b
I have named it the NOT YET

we will se if anyone else uses that
or comes up with a better name

"NOT YET"? This is what you have in reply to the profound insight expressed in my post? :rofl: That is perhaps the most wisecrack remark i read for the past 3 mouth. Where were you?

jackle Jan22-06 04:33 AM

Quote:

Quote by kant
If the universe is expanding/stretching, what is it expanding/stretching into? Is it nothingness?

A Big Rip, Big Crunch or Big Freeze perhaps? If the fate of the universe interests you, I have found a wikipedia article for you:

http://en.wikipedia.org/wiki/Ultimat...f_the_Universe

Note that the universe has a shape and there isn't normally considered to be a space outside this.

Quote:

Quote by kant
Or rather is it is 'nothingness' only in the sense that we cannot give it a word or a definition?

'Nothingness' in physics is usually called 'vacuume' and there is a lot of it out there. I find Wikipedia really good for physics, so here is another link:

http://en.wikipedia.org/wiki/Vacuum
(Vacuume in space and quantum mechanical vacuume sections)

Quote:

Quote by kant
Where did all the mass-energy in the universe came from? Did it came
from nothing? Of course, the last question is absurd.
Since we define the universe as being everything( EX: energy-mass,all the temporal and spatial concepts), then it makes little sense to imagine something 'outside' the universe, or 'before' the big bang.

Yeah, this is true. I think it does make sense to ask what the universe was like at t=0 (just not before). A popular answer is that it came from nothing. I've heard people claim that it came from a quantum vacuume fluctuation.

Quote:

Quote by kant
To make such inquiry, to me, is merely a limitation on language itself. There in fact a deeper level of human consciousness or intuition; A feelings/sense/mind s-eye that give us the conviction that there is 'something' out there. Something that our langauge cannot take us.

This has always been the case through the history of humanity. People still inquire and through that we learn.

I hope I have addressed your questions at the right level and that you enjoy the articles I have referenced.

kant Jan22-06 05:57 AM

Quote:

A Big Rip, Big Crunch or Big Freeze perhaps?
Perhaps not what i was asking, but thanks for the reading.

Quote:

'Nothingness' in physics is usually called 'vacuume' and there is a lot of it out there. I find Wikipedia really good for physics, so here is another link:
humm.. From you link, the concept of vacuume is define as a 'volume of space', but the 'space' here is a spatial concept defned only within the universe. In other word, vacuum inself has no meaning for something 'outside' ....

Quote:

Yeah, this is true. I think it does make sense to ask what the universe was like at t=0 (just not before). A popular answer is that it came from nothing. I've heard people claim that it came from a quantum vacuume fluctuation.
i read that these quantum fluctuation demands the presents of spaces, and all the implication that comes along with space( may be a larger unverse?). So perhaps our universe exist within a larger universe, and 'that' universe itself must exist in a 'larger larger' universe. To continue this line of reason, it is apparent that theory leads to absurdity, because our question is still open. Where did all the mass in all these universes came from?

Mike2 Jan22-06 10:05 AM

Quote:

Quote by kant
Perhaps not what i was asking, but thanks for the reading.
humm.. From you link, the concept of vacuume is define as a 'volume of space', but the 'space' here is a spatial concept defned only within the universe. In other word, vacuum inself has no meaning for something 'outside' ....
i read that these quantum fluctuation demands the presents of spaces, and all the implication that comes along with space( may be a larger unverse?). So perhaps our universe exist within a larger universe, and 'that' universe itself must exist in a 'larger larger' universe. To continue this line of reason, it is apparent that theory leads to absurdity, because our question is still open. Where did all the mass in all these universes came from?

I don't suppose that the universe could collapse back into nothing. For that would seem to violate causality -something producing nothing. In philosophical terms that would be a "denial of the consequences".

So I wonder if space shrinking at all would be the same denial of consequence, violation of causality. Must the universe only expand and not contract?

kant Jan22-06 12:59 PM

Quote:

I don't suppose that the universe could collapse back into nothing. For that would seem to violate causality -something producing nothing.
Hmm.. I don t see it that way. Let say that our universe is merely one out of many cycles of the universe being birth-collapsed back onto inself. This could be mean that the total energy-mass of the universe say stays the same in such perpetual state. Now, our question still remaind ' Where did all the mass-energy came from out of these cycles of birth/collapse of the universe'?. 'When' did this 'cycle' 'began'?

jackle Jan23-06 11:45 AM

I think you can use General Relativity to show that you can create matter out of nothing provided you satisfy conservation of energy by creating an equal and negative amount of gravitational energy. I think this is what most current Big Bang models are based on (a practicing physicist on here can confirm this).

If this is so, I assume that the Big Crunch ideas are based on something like the reverse happening. I heard of one theory where the universe had a different amount of matter in each cycle and evolves differently based on QM fluctuations in the early moments of the universe. I liked this idea a lot.

Chronos Jan24-06 02:53 AM

It is not that far fetched that the universe sprang from 'nothing'. Here are some interesting reads on that topic:

A Universe from Nothing
http://www.astrosociety.org/pubs/mer...2/nothing.html

Birth of the Universe
http://zebu.uoregon.edu/~js/ast123/lectures/lec17.html

Simple quantum cosmology: Vacuum energy and initial state
http://arxiv.org/abs/gr-qc/0501014

Spontaneous Inflation and the Origin of the Arrow of Time
http://arxiv.org/abs/hep-th/0410270

Mike2 Jan24-06 10:53 AM

Quote:

Quote by jackle
I think you can use General Relativity to show that you can create matter out of nothing provided you satisfy conservation of energy by creating an equal and negative amount of gravitational energy. I think this is what most current Big Bang models are based on (a practicing physicist on here can confirm this).
If this is so, I assume that the Big Crunch ideas are based on something like the reverse happening. I heard of one theory where the universe had a different amount of matter in each cycle and evolves differently based on QM fluctuations in the early moments of the universe. I liked this idea a lot.

What I'm suggesting is that spacetime seems to have the property that it expand; otherwise the universe would never have grown from the initial singularity of spacetime. If that is an essential property of spacetime, then it cannot contract. For then it would no longer be spacetime; it will have changed its properties into something else. If that should happen, then what would become of causality?

Garth Jan24-06 11:30 AM

Quote:

Quote by Mike2
What I'm suggesting is that spacetime seems to have the property that it expand; otherwise the universe would never have grown from the initial singularity of spacetime. If that is an essential property of spacetime, then it cannot contract. For then it would no longer be spacetime; it will have changed its properties into something else. If that should happen, then what would become of causality?

I'm afraid this is mistaken.
Space-time does not expand, as time is included in the 4 dimensional manifold space-time is necessarily static.

In the cosmological solution of Einstein's GR field equation, when the universe is considered homogeneous and isotropic, space surfaces within space-time expand or contract as time increases.

The fact that Hubble red shift is observed is interpreted as evidence that we are in an expanding phase of the universe's history at the moment. If the gravitational forces between matter in the unverse are strong enough that expansion may stop and turn into contraction leading to a 'Big Crunch'. If Dark Energy is brought into the equation that demise may be different according to the particular model favoured.

Causality rules O.K?

Garth

Garth Jan24-06 11:47 AM

Quote:

Quote by kant
If the universe is expanding/stretching, what is it expanding/stretching into? Is it nothingness? Or rather is it is 'nothingness' only in the sense that we cannot give it a word or a definition?

Think of this 'toy' model for a moment: Consider, as a thought experiment, a finite, spherical space universe with more than enough mass for closure.

The radius of that hyper-sphere increases with time and can be taken as a measure of the age of the universe at any particular moment in its history.

Embed all such hyper spheres, one within the other, and focus on the universe at our particular moment of time.

What is outside our universe? Answer: a larger, i.e. a later universe.

What is inside our universe? Answer: a smaller, i.e. an earlier universe.

What is the universe expanding into? Answer its future!

What has the universe expanded from? Answer its past!

Quote:

Where did all the mass-energy in the universe came from? Did it came from nothing? Of course, the last question is absurd.
Not at all, the total energy budget of positive matter-energy and negative gravitational energy is often described as zero. Not only might the universe have come from nothing, its sum total might still be nothing!

Garth

jhe1984 Jan26-06 11:48 PM

Stephen Hawking talks about this somewhere in his book. He says that he often gets asked, "what was going on before the Big Bang singularity?" And he writes that not only does he not have an answer, but he doesn't think that such a question can have an answer in that whatever is beyond that singularity (if indeed it is a true singularity) can never be known.

As far as I can reason, there will always be a singularity at some point if our human observations and experiences are functional at that level of reality. Basically, it had to start somewhere.

But personally - and I can't back this up - I think it is best summed up in the Bible when God refers to himself as I AM. We are cause HE is, which means simply HE is. Don't quite understand it, but I like it.

Sorry to bring religion into this. :devil: :surprised:

PS - I'm working on a book that touches on this topic, minus the religion part. So far the questions to answers ratio is about 100 to 1. Ha.


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