Big Bang Theory (GCSE Physics)

Big Bang Theory

Expansion of the Universe

As we learnt above, red-shift shows that galaxies must be moving away from each other. Therefore red-shift can provide evidence for certain scientific theories. For example, if the galaxies are moving away from each other, this must mean that the universe is expanding, which means that it must also support the Big Bang theory. We will be exploring this idea more in the next section.

The Big Bang Theory

At the beginning of the universe, scientists think that all matter was condensed into a tiny area. This area was very hot and very dense.

At some point, there was a big bang, when the hot, dense area of matter exploded. The matter all began to move away from each other, meaning that the ‘universe’ at that point was expanding.

From our observations of the wavelengths of light from distant galaxies (red-shift), we know that the universe is still expanding today. This provides evidence to support the Big Bang theory.

Cosmic Microwave Background Radiation

As well as red-shift, cosmic microwave background radiation (CMBR) provides evidence for the Big Bang Theory. By now the heat produced from the Big Bang originally should be scarcely spread across the Universe.

In support of this prediction, CMBR can actually be found all across the Universe. CMBR is usually found at a temperature of around -270°C.

Therefore the discovery of CMBR also contributed to the Big Bang Theory becoming the currently accepted model.

The Steady State Theory

There is another theory which is less well recognised and accepted compared to the Big Bang Theory – the Steady State Theory.

This theory suggests that the universe has always existed and is expanding, as galaxies are moving away from each other, therefore is supported by the red-shift.

However the evidence from CMBR does not support the Steady State Theory, so the Big Bang Theory remains the currently accepted model for the origin of the universe.