what is the big bang theory ?

Question: what is the big bang theory ?
- Keywords:
  big bang,
  big bang theory,
  space
Asked by Ahmed #21 to David, Eva, Kate, Nicholas, Rachel on 14 Nov 2015.
- Nicholas Pearce answered on 14 Nov 2015:
  
  Hey,
  
  The big bang theory is the idea that the entire universe was once very small – all of it inside a single point. This point contained all the energy in the universe expanded outwards eventually getting cold enough to form atoms, stars and galaxies. Scientists have even seen a echo from the big bang coming from all parts of the universe!
  This is a brilliant video that will explain in more detail if you like:

Question: what is the big bang theory ?