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hmmm ur 2nd questnz lyk dis>>>>>>>
there are stars all around us. Why doesn't the light from all of them combine to make the sky bright? It turns out that if the universe was infinitely large and infinitely old, then we would expect the night sky to be bright from the light of all those stars. Every direction you looked in space you would be looking at a star. Yet we know from experience that space is black!
rite ???????? ..................
wel...........
This paradox is known as Olber's Paradox. There is an apparent contradiction between our expectation that the night sky be bright and our experience that it is black.
Many different explanations have been put forward to resolve this paradox. The best solution at present is that the universe is not infinitely old. Astronomers are still arguing but most agree that the universe is only about 10-15 billion years old. That means we can only see objects as far away as the distance light can travel in 10-15 billion years. The light from stars farther away than that has not yet had time to reach us and so can't contribute to making the sky bright.
hope i helpd u........... 
Its not only expansing but also accelerating.
It implies that the velocity at which a given galaxy is receding from us should be continually increasing over time, as given by Hubble's law.
There are several models to explain this but no clear cut self explanatory theory as of now
Models attempting to explain accelerating expansion include some form of dark energy: Cosmological Constant, Quintessence, Dark Fluid or Phantom energy. The most important property of dark energy is that it has negative pressure which is distributed relatively homogeneously in space. Divergent expansion Phantom energy in a scenario known as the Big Rip causes an exponentially increasing divergent expansion, which overcomes the gravitation of the local group and tears apart our Virgo supercluster, it then tears apart the Milky Way Galaxy, our solar system, and finally even atoms. Measurements of acceleration are thought crucial to determining the ultimate fate of the universe, however we should expect the implications of such a major discovery to develop slowly over many years in the same way the big bang model has continued to develop.
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wel.........nice question............
hmmm............. its not dat easy da way it seems..........sumtyms such simple things makes us think a lot..........
coz on evry statement one can hav a debate.......coz acc 2 me.......expansion of universe z sumthin much more theoreticl n da practical observations n other theories contradict assumptions / xplanations of 1 nother................
wel 2 answer 2 ur question of xpandin universe ,acc 2 me da following answer seems correct 2 da gr8tst xtent............
According to the prevailing scientific model of the Universe, known as the Big Bang, the Universe expanded from an extremely hot, dense phase called the Planck epoch, in which all the matter and energy of the observable universe was concentrated. Since the Planck epoch, the Universe has been expanding to its present form, possibly with a brief period (less than 10−32 seconds) of cosmic inflation.
Several independent experimental measurements support this theoretical expansion and, more generally, the Big Bang theory.
Recent observations indicate that this expansion is accelerating because of dark energy, and that most of the matter in the Universe may be in a form which cannot be detected by present instruments, and so is not accounted for in the present models of the universe; this has been named dark matter.