The Mystery of Dark Matter
If you look at the night sky, you'll often see stars moving very quickly. In fact, they move much more quickly than they should according to their size and the laws of physics. Scientists do not completely understand why the speed of these stars is so high. But many believe the reason is that much of the universe is made up of something called "dark matter". Groups of stars called galaxies, such as the Milky Way, might even consist of ninety per cent dark matter.
How much something weighs depends on where it is. The same object weighs only half as much on Mars as it does on Earth and almost three times as much on Jupiter. So scientists prefer to talk about the mass of something rather than how much it weighs, because mass does not change. They can work out the mass of galaxies by measuring the distance between them and the speed they move. Recently, Dr. Jorge Penarrubia and a team from Edinburgh University discovered something interesting. The mass of the Milky Way is only half as much as the mass of another nearby galaxy, Andromeda. This seems strange, but dark matter may explain why.
Finding out more about dark matter could help us understand how the universe began, but this is not easy. Lots of scientists with different types of expert knowledge are working on the problem. The Edinburgh team is working with many other universities like the University of British Columbia.
We can't see dark matter, it's very difficult to measure and we can't find out its mass. Unlike stars, dark matter doesn't produce or reflect light. But we can make a good guess that it is there because of the way things move and the way light bends. Experts now think dark mater may be very different from the mater which we find on Earth. There may also be five times as much dark matter in the universe as ordinary matter.
The Swiss scientist Fritz Zwicky first gave dark matter its name in the nineteen-thirties. Researchers have been looking for it ever since. Today, technology such as the Large Hadron Collider is collecting more and more information but this technology cannot tell us everything. New ways of finding dark matter will be needed. Investigating dark matter may even mean we will need to start asking questions about the way we look at the universe, including the ideas of Albert Einstein.
