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Stars and the Universe

What is the Big Bang?

The "big bang" is the most widely accepted theory
explaining how the Universe began.

The theory suggests that a long time ago (about 14 billion years)
the Universe started as a big explosion. All the energy
and matter which exists today came from this original explosion.

The evidence for this theory comes from two observations.
1.  Light from stars in other galaxies is red-shifted.
2.  There is cosmic microwave background radiation (CMBR)
everywhere in space.

You don't need to be able to explain the CMBR,
just know that it exists.
Clever scientists did some mathematical calculations
on what would have happened in the big bang.
Their calculations showed that there should be
a low level of microwave radiation as a result of the
original explosion. When they looked out into space they
found this background microwave radiation everywhere.
The big bang is the only theory which explains the CMBR.

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