- WASHINGTON (Reuters) - Understanding the universe, already hard to do, just
got a little harder on Thursday with news that a strange force seems to
be pushing it apart. The unusual repulsive force seems to be working against
gravity to speed up the expansion of the universe, they said. ``We are
scratching our heads to think if there could be a alternative explanation
for it -- something more mundane than a repulsive force,'' said Adam Riess,
a cosmologist at the University of California at Berkeley. Riess and other
members of the High-Redshift Supernova Search Team, an international group
of astronomers from the United States, Latin America, Australia and Europe,
were looking at supernovae. These exploding stars are so bright and so
common that they provide useful information about the universe.
Because space is so vast, the light and other radiation from objects that
are very far away take millions of years to reach Earth. Astronomers can
compare information from distant supernovae to ones that are closer to
get information about what the universe is doing. ``The supernovae tell
us how fast the universe is expanding now and can tell us how fast the
universe was expanding some 5 to 7 billion years ago,'' Riess said in a
telephone interview. Robert Kirshner, an astronomer at the Harvard-Smithsonian
Center for Astrophysics in Massachusetts, said it means the universe is
even more complicated than anyone thought. ``If it's confirmed by other
results and other approaches to the problem it's going to tell us there
is something important, another constituent to the universe,'' he said.
It would be something very strange. Unlike matter, which slows down and
creates less pressure as it fills space, this would move faster.
``That's very weird,'' Kirshner said. ``But it's not unprecedented that
weird things might be true things.'' The team expected to find that the
expansion of the universe is slowing. Big Bang theory holds that the universe
burst from a pinprick of matter between 11 and 15 billion years ago and
is still exploding out. What cosmologists want to know is will it keep
expanding forever or will gravity slow it down, perhaps into a Big Crunch?
To their surprise, Reiss and his collaborators found the universe is actually
expanding faster now than it was 5 to 7 billion years ago. ``It actually
seems to be accelerating so it will be expanding forever,'' he said. Kirshner
said a fifth force could be at work. Modern physics generally recognizes
four forces -- the strong force, which holds the nucleus of an atom together,
the weak froce, which is responsible for atomic decay, the electromagnetic
force, which holds electrons in orbit in an atom, and gravity. The idea
of a fifth force has been tossed around by physicists before, he said.
``They have impossible ideas before breakfast,'' he added.
``The interesting thing is that some of these funny-sounding ideas might
turn out to be right.'' And a similar force is supposed to have existed
-- a fraction of a second after the Big Bang. ``The physics are the same.
We are talking about something that keeps pushing,'' Kirshner said. Reiss
said he was not surprised that no one had noticed the new force before.
``The force is very weak on a small scale and it only becomes important
when you are looking back,'' he said. Plus technology was making it easier
to do such measurements. ``Now we have the (orbiting) Hubble Space Telescope
and the Keck telescope in Hawaii, which are great instruments for this.''
Kirshner said astronomers all over the world would be trying to duplicate
the findings. ``It's something that you can be sure will stimulate a lot
of thought by smart people,'' he said. ``I don't think serious, sober scientists
are going to believe this for a while.''
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