Nearly all inflation models predict that the total ( matter + energy ) density of the universe should be very close to the critical density.
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If we use the critical density of the universe ( that density of mass-energy necessary for SamuelRiv 03 : 40, 2 November 2007 ( UTC)
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In short, at the critical density, expressed as omega equals one, the universe would be in a state of equilibrium between collapse and eternal expansion.
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Still, some scientists cautioned against writing off the possibility of an open universe _ what if there is not enough vacuum energy to reach critical density?
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But so far, all measurements of cosmic mass fall well short of critical density, presumably indicating an open universe on its way to the big chill.
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Such a critical density, an average throughout space of one hydrogen atom in every 10 cubic meters, is usually expressed by cosmologists as omega equals one.
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If, as it now seems, the universe falls considerably short of critical density, theorists have already begun to add to their equations something called the cosmological constant.
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The National Academy of Sciences, summarizing the professional view, noted widespread agreement that two bands of LEO space 900 to and were already past critical density.
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In the new simulations, the " best buy " model, Frenk said, was one that assumed a universe containing only 30 percent of omega, or critical density.
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If dark matter exceeds a critical density, the added gravitational power would cause the universe to collapse in what is being called the " big crunch ."
