The Big Bang Theory
Example of how the universe is expanding
According to the 'Big Bang Theory' The big bang happened about 13.77 billion years ago. The big bang by definition is a giant explosion which spread mass and energy through the entire universe. Everything we know of was originally a very small ball of mass and energy until this happened and spread everything out. The theory states that every started expanding from the big bang and to this day is still expanding. This means that everything is always either getting closer to us or getting further away from us.