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robross
2009-May-06, 02:54 AM
Ok, in a pre-dark energy physics, we still had the concept of "vacuum" energy, and this energy was present in all space. Space is expanding, creating more space. Does this mean more "vacuum" energy is coming into existence in our universe? If so, doesn't this mean the total energy of the universe is increasing over time? Or am I missing something? And if it is increasing, doesn't this mean energy is not being conserved?

Now that we have discovered/noticed "dark energy", how does this relate to vacuum energy? Is this an additional form of energy driving expansion that we didn't recognize before, or is this thought to be related somehow to the vacuum energy which we already knew existed? And again, does the creation of new vacuum cause more energy to be created in the universe as time goes on?

And if the total energy of the universe is still considered to be conserved, how do we balance the "new" energy from the new bits of vacuum/dark energy that are being constantly created?

And for the long shot question for which I already suspect the answer is "We don't know", what is causing new space to be created, and where does the energy for this creation of new space come from? And does it make sense to ask "where does this new space come from", which might imply it was someplace else before it got inserted into our universe?

Thanks!

Rob

m74z00219
2009-May-07, 08:23 AM
I'm probably mistaken, but doesn't QM show that any finite volume of space has infinite energy?

Htorne
2009-May-07, 12:02 PM
I recomend the 2007 book

Endless Universe

http://www.amazon.com/Endless-Universe-Beyond-Big-Bang/dp/0385509642

By:

Paul J. Steinhardt
http://wwwphy.princeton.edu/~steinh/webbrief/

and

Neil Turok

http://en.wikipedia.org/wiki/Neil_Turok

trinitree88
2009-May-07, 03:55 PM
The vacuum energy density is one of those cosmological consequences that happens to be off by a mere 120 orders of magnitude....:doh:yet some peolple still think it exists. You'd notice the gravitational effects of an energy density that high. pete

icarus2
2010-Jul-16, 03:24 PM
From Sean Carroll -(Sean M. Carroll is a senior research associate in the Department of Physics at the California Institute of Technology. He is a theoretical cosmologist specializing in dark energy and general relativity.)

He says that energy is not conserved.
http://blogs.discovermagazine.com/cosmicvariance/2010/02/22/energy-is-not-conserved/

Cougar
2010-Jul-16, 10:51 PM
Ok, in a pre-dark energy physics, we still had the concept of "vacuum" energy, and this energy was present in all space. Space is expanding, creating more space. Does this mean more "vacuum" energy is coming into existence in our universe? If so, doesn't this mean the total energy of the universe is increasing over time? Or am I missing something? And if it is increasing, doesn't this mean energy is not being conserved?

Yes. Yes. No. Yes. I think your logic is correct. Apparently conservation of energy is a local law and does not apply to the universe as a whole.


Now that we have discovered/noticed "dark energy", how does this relate to vacuum energy?

Well, since we know precious little about dark energy, we don't know how/if it relates to the expansion and/or the vacuum energy. It seems logical that it would be closely related, since both appear to 'operate' on every point of space, but again - unknown.


And for the long shot question for which I already suspect the answer is "We don't know", what is causing new space to be created...

The expansion. :)


...where does the energy for this creation of new space come from?

Well.... it has long been thought, I think, that the residual momentum from the big bang is driving the expansion. This may be right, or the vacuum energy may play a much larger role in the expansion + acceleration....

Cougar
2010-Jul-16, 10:53 PM
I recomend the 2007 book Endless Universe By Paul J. Steinhardt and Neil Turok

Yes, I concur. That's a good one.

Cougar
2010-Jul-16, 11:09 PM
Apparently conservation of energy is a local law and does not apply to the universe a s whole.

Well, after reading Sean Carroll's article on this (thanks, Icarus), I guess energy is not even conserved locally. I certainly trust Carroll's position on this rather than my limited understanding.

By the way, I recently picked up Carroll's new 2010 book From Eternity to Here, the quest for the ultimate theory of time. It looks to be good. It's certainly contemporary!

Kwalish Kid
2010-Jul-26, 12:56 AM
The vacuum energy density is one of those cosmological consequences that happens to be off by a mere 120 orders of magnitude....:doh:yet some peolple still think it exists. You'd notice the gravitational effects of an energy density that high. pete
Well, the 120 orders of magnitude thing is really over-hyped. Carroll et al. found one way to calculate the energy density of the vacuum from quantum field theory, using a number of plausible, but not established, assumptions.

Ken G
2010-Jul-26, 02:18 AM
From Sean Carroll -(Sean M. Carroll is a senior research associate in the Department of Physics at the California Institute of Technology. He is a theoretical cosmologist specializing in dark energy and general relativity.)

He says that energy is not conserved.
http://blogs.discovermagazine.com/cosmicvariance/2010/02/22/energy-is-not-conserved/That's a pretty nice article, I think it makes a convincing case. And above all, it makes it clear that the issue is all about pedagogy-- the language we use to understand something, it's not the physics or its measurable predictions.

Ken G
2010-Jul-26, 02:25 AM
Well, after reading Sean Carroll's article on this (thanks, Icarus), I guess energy is not even conserved locally. !I think that too is a matter of language more than anything else-- CMB photons do redshift, and they do get redder anywhere you are, but they don't come from local processes, they come from great distances. If you did not have any access to anything happening at any large distance, you would never see anything that didn't conserve energy, no matter what the universe as a whole was doing. So if by "local", we mean "all that exists that remains local", I think we can still say that energy is conserved locally. But if we include local observations of things that are homogeneous yet coming from great distances, then we don't get energy conservation, unless we build it right into gravity on purpose, as Carroll says. On the other hand, that's always how we got energy conservation in the first place, in the presence of gravity-- even in Newton's day.