A team of U.S. scientists has found the first direct evidence of the existence of “dark matter,” a little-understood substance with a big influence on gravity, the team's leader said Tuesday. Scientists still do not know what exactly dark matter is, but have theorized that it must exist to account for the amount of gravity needed to hold the universe together. They estimate that the substance accounts for 80 to 90 percent of the matter in the universe. Planets, stars, gases, asteroids, and comets make up the rest. Now researchers led by University of Arizona astronomer Doug Clowe say they have evidence to support their theories. Using orbiting telescopes, the researchers watched two giant gas clouds collide over a 100-hour period. As the clouds collided, they said, the visible gas particles slowed, pulling away from the invisible dark matter particles. The researchers said they could detect the dark matter particles by their gravitational pull on the surrounding visible particles. “This is the first time we've been able to show that [dark matter] has to be out there,” Clowe told Reuters. “We haven't actually been able to see the dark matter particles themselves, but what we have been able to do is … image the gravity that they're generating.”
