Question: is there any valid evidence proving that the universe was created by the big bang theory?

Evan Keane answered on 15 Jun 2011:

Another great question! Yes, there is much evidence that the idea of the big bang, i.e. that the universe as we know it began 13.7 billion years ago and has been expanding since.

One piece of evidence is that when you look at many 1000s of galaxies you find that they are all red-shifted. I explained what redshift was here: http://ias.im/44.669 but it basically means that all the galaxies are moving away from us. This shows that the Universe is expanding. If we think about this happening in reverse (rewind the expansion in our mind!) we get to the situation where everything was crammed together at some point. If you work out the speed of the expansion (which you can measure from how redshifted the galaxies are) you can work out how long ago it was when we were all in the same place, and this is where the 13.7 billion years comes from.

Another piece of evidence is the “cosmic microwave background”. Now what is that? It is microwave radiation (the same wavelength as in a microwave oven!) which is detected from all parts of the sky. Because it is from all directions we call it “background” and the “cosmic” bit is because it is coming from space. When the Universe was much smaller it was squished into less space so was much hotter and light was produced. The whole Universe was a blob of charged particles and light (a “plasma”). When it cooled down the particles began to form atoms like we know today, and the light escaped, in all directions. Over time this light cooled down and the temperature of this radiation today is just 3 degrees above absolute zero (that’s -270 degrees celsius – very cold!!). When we look at this light over the whole sky, the differences from one place to the next look exactly as they should for a very hot gas with quantum “wiggles”, which has expanded over time from an initial big bang.

The way galaxies are distributed in the Universe also agrees with what we would expect if the Universe started with a big bang, so that’s another thing.

Oh ya, I think you can also work out much hydrogen and helium and lithium etc. there should be in the Universe if the big bang happened and these numbers are the same as what we observe.

So, all those pieces of evidence, and probably other bits that I am not aware of, are the evidence that the big bang happened. There is no other idea that we have that can explain all of those things.

🙂