Planets and the big bang

Welcome:

The Big Bang Theory

3D illustration of the Big Bang

The Big Bang Theory describes how scientists think the Universe was created.

There is a lot we don’t know about this yet, which is why this is still only a theory! However, it explains a lot about patterns in the Universe.

The Beginning

At the beginning, the universe was a tiny ball that contained a huge amount of energy. Scientists believe this ball was much smaller than a pinhead!
This ball was so dense and so hot that it exploded about 14 billion years ago. The universe was created!
The Big Bang created time, matter and space. Before that, space didn’t exist.

After the Big Bang

As the Big Bang was an explosion, everything was propelled outwards. Today, it is still moving that way. The Universe is expanding all the time.
Just after the explosion, the Universe was incredibly hot. It began to cool.
After 3,000 years, the Universe was cool enough for atoms to form. This included gases like helium and hydrogen, which are key to our survival in the Universe.

Why do Scientists Think the Big Bang Happened?

3D render illustration of universe

There are many reasons scientists think that the Big Bang is a good explanation for how the universe was created:

It is expanding and growing larger all the time, with galaxies moving away from each other. This fits with the theory that it started with an explosion.
They have also measured the amount of radiation and the amount of helium and hydrogen in parts of the Universe. These are also consistent with an explosion.

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