Question: Whilst there is considerable evidence to prove the Big Bang theory, are there any other theories as to how the universe began that are currently being considered, which could one day disprove the Big Bang?

Julian Onions answered on 19 Nov 2014:

Yes – there are other theories of how the universe began, but because of all the evidence we have, they tend to look a little bit like the big bang in some respects.
One of my favourites is the Ekpyrotic universe
http://en.wikipedia.org/wiki/Ekpyrotic_universe
which was nearly killed off this year after an experiment BICEP2 seemed to rule it out, however there is now considerable doubt if it really did, so I’m still carrying a flag for this model.
There is a great readable book written on it too, called Endless Universes.

It basically makes our universe stretch out thinner and thinner and then collide with another universe which causes new matter to appear and looks a lot like a big bang. Except in this model its cyclic, meaning it happens over and over. However each universe created lasts for trillions of years, so to us it looks much like the big bang.

There use to be a steady state universe model, with no big bang (or even start) but that has fallen out of favour because most new data lines up extremely well with a big bang model. It still has a few supporters but they struggle to explain many things.

So, the big bang is by the far the main theory.