Andrew Watson
For the past 20 years, astronomers have had compelling evidence that there is more to the universe than meets the eye: About 90% of the mass of the universe seems to be invisible. This "dark matter" could consist of dim stars, not bright enough to be seen from Earth. It could simply be neutrinos. But there is a more exotic alternative: Dark matter could be made up of massive particles yet to be discovered, collectively known as WIMPs, and a new wave of experiments is now coming on line to catch one.