The Expanding Universe

Theories of the origin of the Universe have had to take into account:

• that light from other galaxies is shifted to the end of the spectrum;
• that the further away galaxies are, the this ‘red-shift’.

Red light has a wavelength than the other colours. This red shift is thought to be due to the effect. This is when waves are compressed together as the source moves towards you and spreads out as it moves away.

Doppler Applet Instructions
Applet made by Rob Scharein

When this happens to light, the compressed wave fronts appear bluer that they would if they were stationary, while the stretched wave fronts look redder - ie they have undergone 'Red Shift':

The current way of explaining this is:

• that other galaxies are moving away from us very ;
• that the further away from us a galaxy is, the it is moving away from us.