6.5 The Big Bang
The Red-shift gives us evidence that the universe is expanding out in all directions.
We can imagine going back in time to see where the universe came from.If it is now expanding outwards, this suggests that it started with a massive explosion at a very small initial point. This is known as The Big Bang Theory.
If the universe began with a big bang, then high energy gamma radiation would have been produced. As the universe expanded, This would have become lower-energy radiation.
Scientists discovered microwaves coming from every direction in space. This is cosmic microwave background radiation (CMBR), the radiation produced by the Big Bang.
The Big Bang theory is the only theory so far, to explain CMBR.