'Dark matter' is real
2006-08-23 11:05
Boston - US scientists have found the first direct evidence of the existence of "dark matter", a little-understood substance with a huge influence on gravity, the team's leader said on Tuesday.
Scientists still do not know what exactly dark matter is,
but have theorised 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%
of the matter in the universe. The more familiar kind
of matter, which can be seen and felt, makes up the rest.
Now researchers led by University of Arizona astronomer
Doug Clowe say they have evidence to back up their theories.
Using orbiting telescopes, the researchers watched two
giant gas clouds in outer space collide over a 100-hour period.
As the clouds clashed, 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, that you can't explain it away,"
Clowe said.
"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."
Some sceptics have argued that dark matter does not exist.
They assert that scientists err in assuming that gravity
exerts the same pull whether holding a plate on a table or
influencing the travel of stars. Revising the laws of gravity
at the interstellar scale would better explain the universe's
structure, they argue.
The latest research is scheduled to be published in an upcoming
issue of The Astrophysical Journal Letters.
- Reuters