What is the Big Bang Theory?

According to the Big Bang Theory, the Universe began as a tiny, tiny dot and grew over billions of years to the enormous (mostly empty) space that’s here today.

The thing is though, the Universe began long before humans were around to see. And we can’t make it happen again. Why then do scientists think the Big Bang theory is probably right?

Scientists can’t run time backwards to see for themselves how the Universe began. But they do see clues in space today that have helped them to come up with a theory.

Here’s Professor Jim Al-Khalili to explain further (watch the video below).

So the Big Bang theory is a theory which is supported by observations. No one saw the Big Bang happening but luckily, there are useful observations to be made by looking at what is here today.

What observations support the Big Bang Theory?”

A clue that really got scientists excited was that they noticed something strange about the light that comes to us from stars a long way away. It’s redder than it should be. Scientists have called this puzzling observation, ‘The Red Shift’. They have also worked out a way to explain why this Red Shift is happening. The explanation includes the idea that space is expanding and that billions of years ago, the Universe was much, much smaller. Furthermore, say scientists, if this explanation is correct, it means that about 14 billion years ago – the universe was smaller than a dot. (OK, that really is VERY small!).