UNIVERSE
SPACE EXPLORATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Open Universe
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Closed Universe
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Flat Universe
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None of the above
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Detailed explanation-1: -If the density of matter in the Universe is low (an open Universe), self-gravity is insufficient to stop the expansion, and the Universe continues to expand forever (albeit at an ever decreasing rate). In an open Universe, locally parallel light rays ultimately diverge.
Detailed explanation-2: -With enough matter, gravity could stop the universe’s expansion and eventually reverse it. This reversal would result in the universe collapsing on itself, not too dissimilar to a black hole.
Detailed explanation-3: -The density of matter decreases as the universe expands because the volume of space increases. (Only a small fraction of matter is in the form of luminous stars; the bulk is believed to be dark matter, which does not interact in a noticeable way with ordinary matter or light but has attractive gravity.)
Detailed explanation-4: -The Big Crunch hypothesis is a symmetric view of the ultimate fate of the universe. Just as the Big Bang started as a cosmological expansion, this theory assumes that the average density of the universe will be enough to stop its expansion and the universe will begin contracting.
Detailed explanation-5: -In such a case, the universe has no bounds, and will expand forever. This is called an open universe. If space has no curvature (i.e, it is flat), there is exactly enough mass to cause the expansion to stop, but only after an infinite amount of time.
Detailed explanation-6: -A popular theory, introduced by Albert Einstein, is that dark energy is a cosmological constant-an unchanging form of energy that’s woven into the fabric of space-time. If that’s the case, and the force exerted by dark energy can never change, then the universe should continue expanding (and accelerating) forever.
Detailed explanation-7: -Astronomers once thought the universe could collapse in a Big Crunch. Now most agree it will end with a Big Freeze. If the expanding universe could not combat the collective inward pull of gravity, it would die in a Big Crunch, like the Big Bang played in reverse.