From the start of big bang our universe is expanding. So it is logical to assume that the expansion will stop someday. Universe has its own momentum and energy by which it is expanding. But someday it may stop and start to collapse due to the gravitational pull of the stars and galaxies.
Scientists are assuming that there is some force that is preventing our universe from collapsing into itself. In order to know that force we have to know the material our universe is made of. Some of us may think we have already known about the materials such as hydrogen, oxygen, electron, proton, neutron etc. But in reality we know very little of the composition of our universe.
Scientists know that our universe is expanding. But how fast? The question hasn't been answered yet. Without knowing this answer it is difficult to predict the fate of our universe. But why? What is the problem of finding the rate of some expansion?
It is very easy to measure speed of something in earth. We calculate the speed by estimating the time required for an object to reach some distance. But measuring the speed of universe is totally different. As light from some star takes millions of years to reach earth, by the time it reaches here the star may have long gone. And we cannot tell the distances it travelled with certainty as it is too far. So measuring the speed is a huge problem for the scientists.
Is there no way to find the speed of our universe?
Hubble telescope above the earth's atmosphere is providing scientists with valuable information which was not possible to obtain. Previously all telescopes were stationed at earth's surface and they have to look into the sky through the earth's atmosphere. As the atmosphere obstructs the view we didn't get a clear image of the sky. But with the help of Hubble telescope we can search the sky without any obstruction. And we get a new look of our universe.
Without Hubble telescope Supernova may never have been discovered. It not only sees the stars and galaxies but also shows us a path to measure an invisible element of cosmos called Dark Matter, which can stop Dark Energy and cause BIG CHILL.