Does an expanding Universe mean more space is being created?

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Offline acecharly

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Im told the universe is growing in size. Does this mean that more space is being created or does it mean the space thats already here itself is expanding/stretching.

Any thoughts

Cheers Ace
« Last Edit: 28/06/2012 22:41:50 by chris »


Offline graham.d

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Re: expansion of the universe
« Reply #1 on: 28/06/2012 09:15:07 »
It depends on the model you want to believe in - the jury will be out a long time on this I think. With the original big-bang model it was generally thought that space-time was expanding; that it was a 4-d hypersphere. In this, it was meaningless to speak of anything outside of such a sphere and that space, and time, began with the big bang. It is generally accepted that space is expanding/stretching; this has to be thought about carefully because the model assumes the universe to be homogenous when in fact it is lumpy (i.e. it has galaxy clusters, galaxies, stars etc.) and these are held together by gravity such that these lumps do not expand in any noticeable way but the space between them does.

The relatively recent measurements suggesting the Universe rate of expansion seems to be accelerating means this model is either defective or there needs modifying by the invention of a "dark energy" component. Nobody knows what form this would take but one idea is that the universe's expansion is creating this energy itself. This may mean that there is something (some sort of "space") that is being uncovered as the universe expands into it. However my understanding is hazy on this as I am rather out of touch. Another idea is that the energy is due to quantum fluctuations (zero-point energy) is quantively out by a factor of 10^80 or so; there are fiddle factors to make this more palatable but it is somewhat unsatisfactory.


Offline Soul Surfer

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A universe with three space dimensions and an attractive mass related force like gravity cannot be stable as a whole or in parts.  Even if it is infinite and very uniformly distributed gas to start with it is like a drawing pin balanced on its point.  Any slight departure from the ideal mass density will result in expansion or contraction and/or condensation into lumps of various kinds.
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