What is the Big Bang theory?

Dr David Krofcheck is a particle physicist who believes that the Big Bang is how matter came about. In this video, David explains how the universe as we know it came about – the Big Bang produced all of the hydrogen and most of the helium present in the universe. He describes the evidence that supports the Big Bang theory.

Point of interest:
The next time you produce, collect, and ‘pop’ a sample of hydrogen in the lab, realise that it was formed about 14 billion years ago in an instant of time after the Big Bang.

Transcript

DR DAVID KROFCHECK
The Big Bang theory essentially states that there was some kind of expansion of space at some distant point in time, approximately 13 and a half, 14 billion years ago. An expansion of space itself.

What did space expand into? I don’t know, I can’t tell you, but there is evidence that galaxies and stars are moving away from each other. We can tell that from the light that gets emitted and detected back on Earth through telescopes, that light is moving away from us, so stars and galaxies and planets are generally expanding away from us.

Big Bang also produced all the hydrogen and most of the helium that we have in the universe. The ratio of helium to hydrogen can be predicted very well with high accuracy by measuring nuclear reactions, and we find that’s just the amount we see when we look out into space. The ratio of the two is just what you would expect from the Big Bang theory.

And there is a left-over signature of the Big Bang as well – cosmic microwave background radiation. That’s the ringing of this big initial expansion. And so the very hot and dense nuclear matter situation at the centre of this expansion and, as hot things do, as it expands, it cools off. So space cools off, and now we are down to the temperature of outer space, which is very low, at near absolute zero, but there is a radiation signature left over that is characteristic of a very high temperature some 13 or 14 billion years ago in the past. So the Big Bang theory encompasses this production of light elements, the recession of distant galaxies that are moving away from us. Big Bang is how matter came about.

Acknowledgements:
CERN
Dana Berry, Skyworks, NASA
NASA/courtesy of nasaimages.org./STScI/G.Bacon
NASA/courtesy of nasaimages.org./JPL-Caltech/R. Hurt (SSC)