Why is the redshift important?

The redshift is an important piece of evidence for the big bang theory. If we look at the visible region on the electromagnetic wave spectrum, we will see there is red light on the left and there is violet on the right. Red light has a longer wavelength than violet light, so this means when a galaxy moves away from us, the wave will 'stretch'. This means the wavelength will increase and galaxy appears red. This is good evidence for the big bang theory, as it can only be explained by the idea that the universe is explanding.