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-   -   Forces Outside Our Observable Universe? (http://www.physicsforums.com/showthread.php?t=245530)

81+ Jul17-08 03:50 PM

Forces Outside Our Observable Universe?
 
Krauss, in his article in the Feb 2008 SciAm magazine stated:

" Two different groups of astronomers traced the expansion of the universe over the past five billion years and found that it appears to be speeding up. The source of this cosmic antigravity is thought to be some new form of “dark energy” associated with empty space. The acceleration of the universe implies that empty space contains almost three times as much energy as all the cosmic structures we observe today: galaxies, clusters and superclusters of galaxies. "

Could it be that forces outside our observable universe are acting on things inside our observable universe in such a way as to cause this acceleration, rather than some expanding "dark energy" inside our observable universe?

Frank

marcus Jul17-08 05:47 PM

Re: Forces Outside Our Observable Universe?
 
Quote:

Quote by 81+ (Post 1804884)

Could it be that forces outside our observable universe are acting on things inside our observable universe in such a way as to cause this acceleration, rather than some expanding "dark energy" inside our observable universe?

David Wiltshire is the main proponent of that view and he has written a number of papers trying to work it out.
Look in arxiv.org under the name Wiltshire, or in slac.stanford database called spires.
I know of it, but am not too familiar with it.

i have the impression it doesn't necessarily work, but is not a bad idea to try out. he ran it up the flagpole a few years ago, if I remember, but not too many people saluted

http://arxiv.org/find/astro-ph/1/au:.../0/1/0/all/0/1

you have to look back down the list to find the first of his papers on this idea

http://www.slac.stanford.edu/spires/...tecount%28d%29
=======================

another thing is acceleration is not the only riddle that a cosmological constant can answer, or that dark energy answers

it also supplies the missing stuff that the General Relativity-based model requires for spatial flatness.
there does not seem to be enough dark matter and ordinary matter so as to explain spatial flatness
and yet galaxy redshift surveys and the CMB indicate space is approximately flat

the amount of dark energy you need to explain the acceleration is also the right amount needed to explain flatness.

so just finding an alternative Wiltshire type explanation for acceleration would still not get rid of all the seeming need for dark energy. it is a complex puzzle.

several research journals have recently devoted entire issues to the dark energy problem.
there is actually no standard story, no consensus. experts are puzzled and disagree. if you are puzzled you are in good company

hellfire Jul18-08 02:35 AM

Re: Forces Outside Our Observable Universe?
 
Quote:

Quote by 81+ (Post 1804884)
Krauss, in his article in the Feb 2008 SciAm magazine stated:

" Two different groups of astronomers traced the expansion of the universe over the past five billion years and found that it appears to be speeding up. The source of this cosmic antigravity is thought to be some new form of “dark energy” associated with empty space. The acceleration of the universe implies that empty space contains almost three times as much energy as all the cosmic structures we observe today: galaxies, clusters and superclusters of galaxies. "

Could it be that forces outside our observable universe are acting on things inside our observable universe in such a way as to cause this acceleration, rather than some expanding "dark energy" inside our observable universe?

Frank

This is a suggestive idea. There are models in which our universe is a part of a higher dimensional space-time. If this space-time in turn has some special properties, then the evolution of its intrinsic curvature may act as a kind of dark energy in our four dimensional space-time, accelerating its expansion. If you are interested search for the work of Gia Dvali.


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