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4 Jan 2012 10:20:59 IST

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Universe

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what is the cause of expanding Universe and Black holes concept?

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Sumiran agrawal

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26 Jan 2012 20:51:03 IST

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It is generally believed that the expansion of the universe is the result of the initial "explosion" of the Big Bang -- the matter created then is still being propelled outwards in all directions.
There were three scenarios for this expansion based on the amount of material in the universes compared to the amount of material necessary to cause gravity to finally pull everything back together again.

Scenario one assumes there is sufficient material in the universe that gravity, acting between every galaxy, every star, every subatomic particle will finally overcome the original expansion and bring all the material together again in the "Big Crunch". What would happen after that is anyone's guess. The universe could swallow itself into some kind of black hole and be gone forever, or it could bounce back as another big bang and oscillate back and forth for all eternity.

Scenario two is the "Big Chill" in which there is not enough material in the universe for gravity to overcome the impetus of the big bang. Expansion would then continue forever with the universe getting larger and larger, dimmer and dimmer, and colder and colder until it finally dies in the deep freeze of absolute (or near absolute) zero.

Scenario three postulates a "Flat Universe". In a flat universe, the amount of material in the universe is just enough for gravity to slow the expansion, but never quite stop it completely.

The ratio of the amount of material in the universe to the amount of material necessary to balance gravity is called omega and is the subject of much discussion and controversy.

shivansh shrivastava

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26 Jan 2012 21:19:27 IST

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It is believd that larg stars end wit f0rmatn of black h0le. . .when whole gravity of a larg body c0ncntrate in a smal body(stars lose mass in th form of energy) th attracti0n it poses doesnt even let light to escape once whn entrd in its vicinity. .as n0 li8 c0me frm that side,th appearnc is black,n namd as black hole. . .

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