The Expanding Universe
[Key Words]
[General] [Open Universe] [Flat Universe] [Closed Universe]
General
There are three main ideas for how the universe is
expanding. They are the ideas of an open, flat, or closed
universe. Out of these ideas, each one will determine how the
universe will end its life. Each one depends on the densityof the
matter there is in the universe. If there is enough, it will slow
down the expansion of the universe, maby even reverse it. The
average density of the universe would only need to be a few atoms
of hydrogen per cubic meter. This ratio is known as  (omega). If
the ratio of the universe is less than one, it will be an open
universe. If it is more than one, it will be a closed
universe. if it is exactly one, it willl be a flat
universe.
Open Universe:
An open universe is where the ratio of is less than one.
In this case, the universe does not have enough matter to stop
its self from expanding. In an open universe, the universe keeps
expanding away from where the big bag took place. Eventually,
galaxies will become very far apart and will all turn into
superlarge black holes. Energy and particles will continue to
evaporate from the black hole. In the last seconds, all that's
left in the black hole will explode with a huge burst of energy.
Eventually, all the matter will be at the same temperature and
nothing will react. If nothing is changing in the universe, there
is nothing to judge the passage of time, and the universe dies of
"heat
death"
Flat Universe:
A flat universe occurs where the ratio of is exactly one. In
this case, the universe has just enough mass to stop its self
from expanding. So in thery, in an infinate amount of time the
universe would stop expanding. Before this could happen though,
it would suffer from a heat death just like an open universe.
Closed Universe:
In a closed universe, the ratio of is more than one.
Here, the mass of the universe would cause the universe to slow
down and reverse the rate at which it's expanding. This would
cause all the matter in the universe to contract in on its self.
This would simulate the conditions that existed during the big
bang. This is known as the big crunch.
Some scientists believe that it would simulate the big bang so
exactly that the big bang would happen again an the universe
would be reborn.
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[Key Words]
[General] [Open Universe] [Flat Universe] [Closed Universe]
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