Astronomy

How the Universe Formed



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HOW DID THE UNIVERSE FORM?

No-one knows for sure is the answer, although there are several thoeries, some more popular and more favoured than others. The Big Bang Hypothesis is the most widely cited and on balance the most likely candidate.



The Big Bang

The age of the Universe is estimated to be about 14 billion years old. This is obtained from several different methods (estimating the ages of the oldest stars and clusters, and the time taken for them to form; also from calculations to measure the expansion of the Universe and figuring how long it would take the Universe to get to the size it is) which show a correlation to the above figure. It is impossible to determine the exact age of the Universe, but we may improve the accuracy of our measurements (the range at the moment is from 10 to 16 billion years, which is a vast difference).

The Big Bang Hypothesis basically says that all the matter and energy of our Universe was, at the very beginning of time (as we measure it, anyway) concentrated into an infinitely small point. Why this was here, why it chose to explode is outwith the realm of science, firmly in the land of fiction. Or, if you believe, religion.

This point then burst outwards, with the pent up energy of our entire Universe and expanded at a collossal rate. (What it burst into, is another unanswerable question.) At this time, because of the small space it had been crammed into, everything was pure energy and had an unimaginably high temperature. Eventually, after some expansion, protons, electrons and photons were discernable, and it is from this that we deduce the Cosmic Microwave Background Radiation (CMBR).

From that time on, from tiny little density differences, mass clumped together. As this happened more mass was attracted, gravity playing its pivotal role. This led to the formation of the first stars. These were massive and burned out much more quickly than our own Sun. When they exploded, in massive catastrophic supernovae, they fired out the ingredients needed to create planets like our own, elements like iron and silicon and carbon, which had not been present at the Big Bang.

Through time, exploding stars and merging galaxies, we get to where we are now...

There are a lot of questions raised by this description of the Big Bang:
What was there before it?
What did the Universe expand into?
Are there other Universes?
How will it all end - will it exist forever or end in a Big Crunch?
We are not likely ever to find answers to these, but they are good points for fiction writers to get their teeth into!

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