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Message: <blockquote data-quote="tharinda07" data-source="post: 3660023" data-attributes="member: 21844">Current value of Ω The value of Ω at the present time is denoted Ω0. This value can be measured in a number of ways since signals from distant objects will be warped by the curvature of the space through which they pass, giving clues as to the current density. One such observation is that of <a href="http://en.wikipedia.org/wiki/Anisotropies" target="_blank">anisotropies</a> in the <a href="http://en.wikipedia.org/wiki/Cosmic_Microwave_Background" target="_blank">Cosmic Microwave Background</a> (CMB) radiation; another is the frequency of <a href="http://en.wikipedia.org/wiki/Type_Ia_supernova" target="_blank">Type-Ia</a> <a href="http://en.wikipedia.org/wiki/Supernovae" target="_blank">supernovae</a> at different distances from Earth.    Data from the <a href="http://en.wikipedia.org/wiki/Wilkinson_Microwave_Anisotropy_Probe" target="_blank">Wilkinson Microwave Anisotropy Probe</a> (measuring CMB anisotropies) combined with that from the <a href="http://en.wikipedia.org/wiki/Sloan_Digital_Sky_Survey" target="_blank">Sloan Digital Sky Survey</a> (observing Ia supernovae) constrain Ω0 to be 1 within 1%. In other words the term is currently less than 0.01, and therefore must have been less than 10−62 at the <a href="http://en.wikipedia.org/wiki/Planck_era" target="_blank">Planck era</a>.    This tiny value is the crux of the flatness problem. If the initial density of the universe could take any value, it would seem extremely surprising to find it so 'finely tuned' to the critical value ρc. Indeed, a very small departure of Ω from 1 in the early universe would have been magnified during billions of years of expansion to create a current density very far from critical. In the case of an overdensity (ρ > ρc) this would lead to a universe so dense it would collapse into a Big Crunch in a few years or less; in the case of an underdensity (ρ < ρc) it would expand so quickly and become so sparse it would soon seem essentially empty, and <a href="http://en.wikipedia.org/wiki/Gravity" target="_blank">gravity</a><a href="http://en.wikipedia.org/wiki/Galaxy_formation" target="_blank">form galaxies</a>. In either case the universe would contain no complex structures such as galaxies, stars, planets and people.would not be strong enough by comparison to cause matter to collapse and    This problem with the Big Bang model was first pointed out by <a href="http://en.wikipedia.org/wiki/Robert_Dicke" target="_blank">Robert Dicke</a> in 1969, and it motivated a search for some reason the density should take such a specific value. </blockquote>

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