The Big Bang Theory (Oxford AQA IGCSE Physics)

Cosmic microwave background radiation (CMBR) is a form of electromagnetic radiation filling the universe

• It comes from radiation that was present shortly after the beginning of the universe

It is detected everywhere throughout the Universe

• The CMBR map is the closest image that exists to a map of the Universe

It shows that the temperature of the Universe, and therefore the objects in it, are more or less uniformly spread out

The CMBR comes from high-energy radiation which originated just after the Big Bang

As the Universe expanded, the wavelength of this radiation increased

• It therefore lost energy and produced the CMBR which can be observed today

Scientists believe the universe began with a ‘big bang’, 14 thousand million years ago

The Big Bang theory is currently the only theory that can explain the existence of CMBR

A giant explosion, known as the Big Bang, caused the Universe to expand outwards

• As each point moved away from the others, the Universe began to cool

• As a result of the initial explosion, the Universe continues to expand

The Big Bang theory is very well supported by two main pieces of evidence:

1. Cosmological red-shift
   This provides strong evidence for the expansion of the Universe

2. Cosmic Microwave Background Radiation (CMBR)
   This provides evidence for the expansion of the Universe and that it had a hot beginning