The Expanding Universe
demonstrate an understanding of the observational evidence for
an expanding Universe
demonstrate an understanding of the past evolution of the Universe and the main
arguments in favour of the Big Bang
demonstrate an awareness of the different evolutionary models of the Universe
(past and future) and why cosmologists are unable to agree on a model.
Imagine a balloon covered in galaxies. As the balloon inflates the galaxies get further apart from each other. Look at the distances between galaxies A and B and between galaxies A and C. You should see that the further apart the galaxies are the faster the are moving away from each other, just as in our Universe. This doesn't mean that our galaxy is in the centre, in fact there is no centre. The same would be true no matter what galaxy you lived in.
The fact that the Universe is expanding suggests that in the past the Universe was a lot smaller than it is now, in fact it could have started in one very very space with a BIG BANG. Not a huge explosion but a very rapid expansion.
Evolutionary Models
- Will the Universe keep expanding forever?
- Will it reach a certain size then stop?
- Will it reach a certain size then start to contract, perhaps ending in a big crunch?
Thanks to dark energy the answer to the first question is probably yes. It was thought that whether it would keep on expanding or not depended on the amount of mass in the Universe and hence the amount of gravity pulling it together and slowing its expansion. One of the Hubble Telescope's main tasks was to measure the amount of matter in the Universe and so get an accurate value for the Hubble constant. This would be the best indication as to which of the scenarios above was most likely.
Scientists have quite recently discovered, thanks to data gained by WMAP, that the rate of expansion is actually increasing. The Universe is likely to keep getting bigger and bigger. Eventually all the nuclear fuel will run out and the Universe will die a cold death.