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# Big Bang 2 and a new beginning of space/time

Author Topic:   Big Bang 2 and a new beginning of space/time
ramoss
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 Message 1 of 33 (664411) 05-30-2012 10:16 PM

I was watching a program that described a hypothetical end to the universe,trillions of years in the future where all the atoms decayed, and even the black holes decayed, leaving the 'big chill'.
Space and time would still exist, would it not ? What would happen if such an environment had an expansion of energy/matter into it.. sort of a 'big bang 2'. How would observers in that 'second big bang' see the universe differently than we do now?
How can we distinguish between expanding into an empty, cold universe that already had 'space' and distance, versus the creation of space/time as the inflationary theory of the big bang says? If, after a bunch of billion years, intelligent creatures evolved, .. how would they know they were part of an older universe that 'chilled out' .. or would it appear to them that space/time formed at the beginning of the expansion of their energy/matter?
Edited by Adminnemooseus, : Changed topic title from "The begining of space/time and the big bang" to "Big Bang 2 and a new beginning of space/time".

 Replies to this message: Message 2 by Adminnemooseus, posted 05-30-2012 10:52 PM ramoss has replied Message 5 by Son Goku, posted 06-28-2012 7:24 AM ramoss has replied Message 7 by Alfred Maddenstein, posted 06-28-2012 3:20 PM ramoss has not replied

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 Message 2 of 33 (664412) 05-30-2012 10:52 PM Reply to: Message 1 by ramoss05-30-2012 10:16 PM

Topic title change suggestion
I originally sent this suggestion to Ramoss as a personal message, but I now think it should be in the topic itself.
Quoting my PM:
Message 1 looks pretty good, but I suggest a topic title change.
Instead of the existing "The begining(sic) of space/time and the big bang", how about "Big Bang 2 and a new beginning of space/time"? Maybe that would help distinguish your topic from the many Big Bang topics that have already happened.
Edited by Adminnemooseus, : See above.
Edited by Adminnemooseus, : Undo previous edit.

 This message is a reply to: Message 1 by ramoss, posted 05-30-2012 10:16 PM ramoss has replied

 Replies to this message: Message 3 by ramoss, posted 05-31-2012 2:46 PM Adminnemooseus has seen this message but not replied

ramoss
Member (Idle past 108 days)
Posts: 3228
Joined: 08-11-2004

 Message 3 of 33 (664413) 05-31-2012 2:46 PM Reply to: Message 2 by Adminnemooseus05-30-2012 10:52 PM

Re: Topic title change suggestion
That sounds good. How do I change the title, or can you edit it when you move it over?
{Historical note - Topic title edits are done via editing message 1. The topic starter or an admin can do such. - Adminnemooseus}
Edited by Adminnemooseus, : See above.

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 Message 4 of 33 (664415) 05-31-2012 6:12 PM

Thread Copied from Proposed New Topics Forum
Thread copied here from the Big Bang 2 and a new beginning of space/time thread in the Proposed New Topics forum.

Son Goku
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 (1)
 Message 5 of 33 (666503) 06-28-2012 7:24 AM Reply to: Message 1 by ramoss05-30-2012 10:16 PM

Subtle issues
An interesting idea and one dealt with in the scientific literature.
First of all I assume that you do not mean matter expanding into a pre-existing space. This can be easily distinguished from our current universe as the motion of matter is not driving the expansion between the galaxies (easily seen to be true as the galaxies show no effects of acceleration).
So I will take you to mean to the following scenario. That there was already space and in a small region of that space some ball of matter began to cause the space in which it existed to expand rapidly (i.e. its section of the larger universe began to expand).
The problem with this is very simple. You simply can't have that amount of matter compressed in a pre-existing universe and then have it expand. Einstein's General Relativity (or even alternate theories of gravity like Brans-Dicke) just don't predict that a ball of matter would evolve like that in pre-existing spacetime. Rather it would collapse in on itself.

 This message is a reply to: Message 1 by ramoss, posted 05-30-2012 10:16 PM ramoss has replied

 Replies to this message: Message 6 by ramoss, posted 06-28-2012 12:43 PM Son Goku has replied

ramoss
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 Message 6 of 33 (666543) 06-28-2012 12:43 PM Reply to: Message 5 by Son Goku06-28-2012 7:24 AM

Re: Subtle issues
Well, wouldn't it be a highly compact amount of energy, rather than matter? Didn't it take a certain period of time for even sub atomic particles to form?
Could you point me to an essay or article on it??
What had stuck me was the description of the 'end of the universe' , where we had gotten into 'the big rip'.. i.e. .. no more stars, or even atoms..nor black holes.
And I thought that the far galaxies DID show effects of acceleration.. as measured by the Ia supernovae in them.

 This message is a reply to: Message 5 by Son Goku, posted 06-28-2012 7:24 AM Son Goku has replied

 Replies to this message: Message 10 by Son Goku, posted 07-01-2012 9:23 AM ramoss has replied

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 Message 7 of 33 (666562) 06-28-2012 3:20 PM Reply to: Message 1 by ramoss05-30-2012 10:16 PM

How do you mean all atoms decayed? Decayed into what?

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1.61803
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 Message 8 of 33 (666570) 06-28-2012 4:19 PM

I always thought that the end of the universe would be when all matter was so spread out and the universe so homogeneous that nothing interacted anymore. delta S= zero.

"You were not there for the beginning. You will not be there for the end. Your knowledge of what is going on can only be superficial and relative" William S. Burroughs

 Replies to this message: Message 9 by ramoss, posted 07-01-2012 9:04 AM 1.61803 has replied

ramoss
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 (1)
 Message 9 of 33 (666909) 07-01-2012 9:04 AM Reply to: Message 8 by 1.6180306-28-2012 4:19 PM

Well, according to some of the shows i saw, even black holes will 'decay' over time, via hawking radiation. .. and so will atoms.

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Son Goku
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 Message 10 of 33 (666911) 07-01-2012 9:23 AM Reply to: Message 6 by ramoss06-28-2012 12:43 PM

Re: Subtle issues
ramoss writes:
Well, wouldn't it be a highly compact amount of energy, rather than matter? Didn't it take a certain period of time for even sub atomic particles to form?
Energy is just a property of matter, not a thing itself. Early in the universe matter wouldn't have been organised into states that we'd recognise as particles, but it was still matter, highly compressed matter.
Could you point me to an essay or article on it??
On what specifically?
And I thought that the far galaxies DID show effects of acceleration.. as measured by the Ia supernovae in them.
They show effects due to the acceleration of the expansion of the universe, but they are not really moving themselves, rather the space they exist in is expanding.

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ramoss
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 Message 11 of 33 (666998) 07-02-2012 1:31 AM Reply to: Message 10 by Son Goku07-01-2012 9:23 AM

Re: Subtle issues
I am beginning to see, through a glass darkly. However , if gravity causes space to bend, why didn't the matter cause the space to bend rather than 'inflate'??
Is that one of the things that 'dark energy' is responsible for, since the expansion of space is accelerating?

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NoNukes
Inactive Member

 (1)
 Message 12 of 33 (667008) 07-02-2012 9:03 AM Reply to: Message 11 by ramoss07-02-2012 1:31 AM

Re: Subtle issues
Gravity does not cause the inflation. It retards expansion, just as your question suggests. I don't know what caused the inflation.

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1.61803
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From: Lone Star State USA
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 Message 13 of 33 (667019) 07-02-2012 11:27 AM Reply to: Message 9 by ramoss07-01-2012 9:04 AM

Hi Ramoss,
Dr. Hawking has retracted the loss of information paradox.
Hawking to dispel black hole 'myth' | Space | The Guardian
Leonard Susskind proposes the information is retained within the event horizon and emitted back as Hawking radiation.
All of this be theoretical physics of course.
Salient point being the conservation of information is preserved in the latter theory.
It seems more plausible that eventually everything will be so spread apart that even light will not reach the observer. The universe will possibly just go dark. Things happen because there are differences. If nothing interacts, nothing happens.

"You were not there for the beginning. You will not be there for the end. Your knowledge of what is going on can only be superficial and relative" William S. Burroughs

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Son Goku
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Posts: 1226
From: Ireland
Joined: 07-16-2005

 (5)
 Message 14 of 33 (667046) 07-02-2012 4:03 PM Reply to: Message 11 by ramoss07-02-2012 1:31 AM

Dark Energy
I am beginning to see, through a glass darkly. However , if gravity causes space to bend, why didn't the matter cause the space to bend rather than 'inflate'??
Matter doesn't really cause space to bend. Rather matter determines what the geometry of spacetime will be.
More specifically the energy density of matter at a point added to the flow of momentum caused by the matter at that point determines the part of the curvature of spacetime which causes balls of particles to shrink over time (The volume shrinking curvature). More detail in this post: Einstein's Equations
Although you can mathematically calculate the spacetime geometry which results from a piece of matter, there isn't really an intuitive way to guess at what it would be like.
For a spherical ball of matter like the Sun the result is something you could call a bending of spacetime (mostly time in this case).
For a homogeneous gas (like the universe on the largest scales) the result is a spacetime where space expands as time passes.
Is that one of the things that 'dark energy' is responsible for, since the expansion of space is accelerating?
In the post I link to above I give the Einstein's equations as: $\color{white} G_{\mu\nu} = 8\pi T_{\mu\nu}$ The term on the right is completely fixed, it is the energy and momentum flow density of matter. On the left-hand side you have a term related to the geometry of space. In this case $\color{white} G_{\mu\nu}$, called the Einstein Tensor. The Einstein Tensor measures the volume shrinking part of curvature.
You can't just put any geometric term on the left hand side, as Einstein realised, since most geometric quantities "diverge". This basically means that they can grow in value at a given point without being compensated by a decrease at another point.
$\color{white} T_{\mu\nu}$ which measures the matter, never diverges (new matter can not just "appear" without a compensating loss of matter elsewhere). So only divergence-less geometric terms can be used, since only they will match the behaviour of $\color{white} T_{\mu\nu}$.
This really restricts the choice of what can be on the left-hand side, down to pretty much just: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} = 8\pi T_{\mu\nu}$
In this equation $\color{white} \Lambda$ is just a number and $\color{white} g_{\mu\nu}$ is the metric, a geometric term describing how distances work in the spacetime.
Einstein, and most people after him had no idea what value $\color{white} \Lambda$ should have. So in most textbooks on general relativity and in research up until the late 90s it was largely ignored and instead we used the equation given above: $\color{white} G_{\mu\nu} = 8\pi T_{\mu\nu}$
This is because the results in most cases aren't really that different. For instance the shape of the spacetime around the sun is virtually identical under the two equations (unless $\color{white} \Lambda$ is unrealistically large).
However for a homogenous cloud of gas (like the universe on the largest scales), the two equations give quite different results. The simpler equations give an expanding universe, however the equations with a positive $\color{white} \Lambda$ give an accelerating expanding universe.
Then basically in 1998 we found that observations of distant stars in our universe match the universe described by the equations with a very small positive $\color{white} \Lambda$.
Now the question is: why does $\color{white} \Lambda$ have the value it has?
There are several different proposals, we just call all of them "Dark Energy", because $\color{white} \Lambda$ has units of "joules per volume", i.e. units of energy density.
Edited by Son Goku, : Small typo

 This message is a reply to: Message 11 by ramoss, posted 07-02-2012 1:31 AM ramoss has not replied

Son Goku
Member
Posts: 1226
From: Ireland
Joined: 07-16-2005

 (2)
 Message 15 of 33 (667261) 07-05-2012 5:27 AM

What is Dark Energy?
I should follow up on the previous approach and attempt to say what exactly is Dark Energy, or rather the two most popular ideas. There is some very bad information out there on this, so I want to carefully explain the two ideas.
Vacuum Energy:
This is probably the most basic, least exotic guess at what Dark Energy is. In the previous post I wrote the Einstein's equations as: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} = 8\pi T_{\mu\nu}$
However the matter here is classical, but we know matter is quantum mechanical. We don't know if spacetime is quantum mechanical (and if it is we don't know how to describe it, that's the problem of quantum gravity). So, to improve this equation in a way consistent with what we know already we make matter quantum mechanical, but keep gravity classical.
Since matter is now quantum mechanical it is probabilistic. Hence, $\color{white} T_{\mu\nu}$ has no definite value and fluctuates. However, gravity is still classical and deterministic, so it cannot interact directly with something fluctuating like this. We need it to interact with a deterministic quantity. Fortunately the average stress-energy $\color{white} \left$ is deterministic.
(Averages are always deterministic in quantum mechanics and behave classically. Also by average I mean that the quantum matter will have a stress-energy $\color{white} T_{\mu\nu}$ that jumps all over the place, but $\color{white} \left$ is the central value about which it fluctuates.)
This leads to the naive semi-classical gravity equations: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} = 8\pi \left$
These are naive, since if you try to solve the equations you get infinities.
This is the problem known as renormalisation. Quantum theories often have infinities if you use the exact same equations as the classical theory. Generally these infinities only disappear when you add new terms to the equation. Basically the quantum theory requires new terms.
It turns out the infinities only vanish if you add two new terms to the equation: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} + \alpha H^{1}_{\mu\nu} + \beta H^{2}_{\mu\nu} = 8\pi \left$
Two interesting things here:

1. Even if I'd started with no cosmological constant, like: $\color{white} G_{\mu\nu} = 8\pi\left$ I would still have ended up with: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} + \alpha H^{1}_{\mu\nu} + \beta H^{2}_{\mu\nu} = 8\pi \left$ in order to remove the infinities. Even if I start off with no $\color{white} \Lambda$, it's automatically generated when I try to get rid of the infinities. That is Quantum matter requires the cosmological constant. So we at least know why it isn't zero.
2. The new terms: $\color{white} \alpha H^{1}_{\mu\nu} + \beta H^{2}_{\mu\nu}$ are geometric terms describing how curvature changes as you move through spacetime. ($\color{white} \alpha, \beta$ are just numbers) At first people found them a bit odd. They make the equations much harder to solve and they're not "natural" quantities by which I mean, aside from removing infinities, they don't seem to have a physical explanation. However they were later discovered to have a very important effect, they make spacetimes containing time-machines impossible. The old classical equations: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} = 8\pi T_{\mu\nu}$ can give rise to time machines with the right $\color{white} T_{\mu\nu}$ on the right-hand side.
This can never happen under the new equations: $\color{white} G_{\mu\nu} + \Lambda g_{\mu\nu} + \alpha H^{1}_{\mu\nu} + \beta H^{2}_{\mu\nu} = 8\pi \left$ Quantum matter does not allow time machines.
There are a lot of things making up $\color{white} \Lambda$:

1. The first is the part coming from when you try to remove infinities that the theory would have even if there was no matter, i.e. infinities that are there even in a vacuum. This is $\color{white} \Lambda^{vac}$.
2. The second part is called $\color{white} \Lambda^{ind}$ (ind=induced). This part comes from infinities relating to:
The masses of the W and Z weak bosons
The strength of the Higgs field
The energy where left-spinning and right-spinning quarks behave the same
The energy where the electroweak force separates into the electromagnetic force and the weak force.
I'll stop here and continue in the next post because it looks a bit less cluttered.

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