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.

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.

This suggests that the whole Universe is __________ and that it might have started, billions of years ago, from one place with a huge explosion we call the __________.

There are many unanswered questions to which cosmologists are searching for answers, for example the nature of __________ that appears to make up much of the Universe�s mass.