The Big Bang Theory
Extended tier only
- Around 13.8 billion years ago, the Universe began from a single point of high density and temperature
- 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
Tracing the expansion of the Universe back to the beginning of time leads to the idea it must have begun with a “Big Bang”
- The Big Bang Theory is supported by many astronomical observations which indicate that distant galaxies are moving away from us
- If galaxies are moving away from us, this means the Universe must be expanding
Expansion of the Universe
Observations of light from galaxies show they are moving away from us which means the Universe is expanding
Examiner Tip
The expansion of the Universe can be visualised by imagining a balloon with equally spaced points on it. The balloon represents space and the points represent galaxies.
When the balloon is deflated (i.e. the Universe was smaller), the points (galaxies) are closer together and are at an equal distance apart.
As the balloon (Universe) expands, all the points (galaxies) become further apart by the same amount.
This is because the space between the galaxies itself has expanded.
