The
universe is about 13.7 billion years old. At its beginning it looked nothing
like it does today. Yet, everything in today’s Universe did exist in some form
back then. It all started with the Big Bang, a kind of massive explosion that
would not only go on to produce all the matter in the Universe but also marked
start of time.
At the
start, the Universe was a hot and dense ball of radiation energy. In
one-thousandth of a second, tiny radiation particles produced tiny particles of
matter. These combined to form the first ever chemical elements, hydrogen and
helium. Some regions of the young universe contained slightly more hydrogen and
helium than others. These shrank to form the first stars. Nuclear reactions
inside the stars produced many other chemical elements, including carbon and
oxygen. The elements in the Universe today were produced from elements created
in the Big Bang.
Everything
in the Universe produces energy – you produce energy when you exercise, and
light energy is produced by nuclear reactions inside stars. In the first
trillionth of a second of the creation of the Universe, the temperature of the
Universe was ten billion trillion trillion degree Celsius.
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We
see objects in space because of their light. Stars produce their own but
others, such as the Moon and planets, shine by reflecting light.
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Light
travels at 299,800 Km per second faster than anything else.
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Distant
stars are seen as they were in the past – when the light left them.
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The
most distant galaxies we see are about 13 billion light years away, and as they
were in the early Universe.
Note that
the Universe is expanding by about 70 km (43 miles) every second. And what
about us, all the elements on Earth, including all the elements in our body,
were produced in stars.
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