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The Big Bang - the beginning of the Universe


Most astronomers now believe that the Universe as we know it began with an unimaginably huge expansion. This happened some 14 000 000 000 years (1.4x1010 years) ago.
We call this the Big Bang.
The age of the universe is therefore 1.4x1010 years.

To try and understand what an immense time ago that was, think of a scale where one metre represents a thousand million years. The age of the Universe is then represented by a distance of around 14m, a million years by 1 mm and one human lifespan by 0.1mm!

We have really no idea what happened before the Big Bang because astronomers think that time and space began at that moment. Before the Big Bang there was no space or time a very difficult idea to grasp.

Anyway we do have some idea of what happened after the Big Bang.

The temperature in that explosion was unbelievably large astrophysicists think it may have been as high as 1000 million million oC! (Compare that with the surface of our Sun at only 6000 oC.)

Moments after the Big Bang (and we are talking here of times less than a million millionth of a second) some of the radiation began to 'turn into' matter the first particles were formed but protons and neutrons did not begin to appear until almost a second after the explosion.

The universe began to cool, just like a lump of red-hot coal cools if put outside on a dark cold night. After about 300 000 years the temperature had fallen to about 6000 oC and the Universe continued to cool.

Some 500 000 years after the Big Bang the Universe had cooled so much that it became dark. The radiation emitted had passed over the barrier between visible and the infrared just like the lump of coal on a dark night. It was still hot (about 700 oC) but the radiation coming from it was too long to see if anyone had been around at that time to look at it!

After about a million years atoms began to form and these had slowly grouped together under gravitational attraction to make the embryo of a star.

Eventually the temperature in the centre of these stars had become high enough for nuclear fusion to take place and about a billion years after the Big Bang the first star was born and blazed out into the darkness of space - there was light!

The stars slowly became grouped together into the great 'island universes' that we know as galaxies and the Universe looked very much like it does today.

 

A VERSION IN WORD IS AVAILABLE ON THE SCHOOLPHYSICS USB
 
 
 
© Keith Gibbs 2020