2.5 - The Origin of the Universe

The Big Bang theory and the age of the universe

• The Big Bang theory is the accepted explanation for how the universe began.
• All the matter in the universe was once concentrated into an extremely small space that was very hot and very dense.
• It then began to expand rapidly, and that expansion of space is still going on today.

The age of the universe

Working back from the rate of expansion gives the universe a finite age of around 14 billion years.

The cosmic microwave background as evidence for the Big Bang

• The cosmic microwave background (CMB) is electromagnetic radiation left over from the beginning of the universe.
• It fills all of space and is key evidence supporting the Big Bang theory.

Discovery and study

• The CMB was first discovered in 1964 using a radio telescope.
• The COBE satellite (Cosmic Background Explorer) measured it from space between 1989 and 1993, providing data that supported the Big Bang theory.