Science Friday

New Data Shows Mysterious Force in Universe, as Einstein Said:

A dark, unseen energy permeating space is pushing the
universe apart just as Einstein predicted it could in 1917, according
to striking new measurements of distant exploding stars by the orbiting
Hubble Space Telescope.
The energy, whose source remains unknown, was named the cosmological
constant by Einstein. In a prediction he later called "my greatest
blunder," but which received its most stringent test ever with the new
measurements, Einstein posited a kind of antigravity force pushing
galaxies apart with a strength that did not change over billions of
years of cosmic history.
Theorists seeking to explain the mysterious force have suggested that
it could, in fact, become stronger or weaker over time � either
finally tearing the universe apart in a violent event called "the big
rip" or shutting down in the distant future. If the force somehow shut
down, gravity would again predominate in the cosmos and the universe
would collapse on itself. That version of oblivion is sometimes called
"the big crunch."
The new observations, which were led by Dr. Adam Riess at the Space
Telescope Science Institute in Baltimore, made the tightest
measurements ever on the strength of the antigravity force over time.
The observations relied on Hubble observations of the exploding stars,
or supernovas, which are swept up in the dark energy's cosmic push.
But rather than seeing the changes in the push that many theorists had
predicted, Einstein's steady, unchanging cosmological constant fits the
data better than any of the alternatives. "What we've found is that it
looks like a semi-permanent kind of dark energy," Dr. Riess said. "It
appears like it's been with us for a long time; if it is changing it's
doing so slowly." "Einstein's theory," Dr. Riess added, "is looking a
lot better than before this data."
While the new results favor Einstein's nearly century-old prediction,
they do not yet entirely rule out the stranger and more changeable
forms of energy that some theorists have put forth. In particular,
scientific proponents of the big rip, in which the energy would
eventually become so powerful that it tears apart planets, stars and
even atoms, have been left with some hope. But the data suggest, Dr.
Riess said, that any ultimate cataclysm could not occur until well into
the distant future, perhaps 30 billion years from now.
The measurements raise new questions about NASA's decision, which is
now being reviewed, to let the Hubble Space Telescope die a slow death
in space over the next several years rather than attempt another
servicing mission with the space shuttle. NASA's administrator, Sean
O'Keefe, has said that a servicing mission would be too risky in the
wake of the disaster involving the Space Shuttle Columbia.
Dr. Riess said he disagreed with the decision to shut down the Hubble.
"The Hubble is an invaluable tool in the studies," he said. "Nothing
else can contribute this kind of data. I think to stop doing this
science with Hubble would be a very unfortunate choice."

The Hubble Space Telescope will be allowed to degrade and
eventually become useless, as NASA changes focus to President Bush's
plans to send humans to the moon, Mars and beyond, officials say. NASA
canceled all space shuttle servicing missions to the Hubble, which has
revolutionized the study of astronomy with its striking images of the
universe. John Grunsfeld, NASA's chief scientist, said Friday that NASA
administrator Sean O'Keefe made the decision to cancel the fifth space
shuttle service mission to the Hubble when it became clear there was
not enough time to conduct it before the shuttle is retired. The
servicing mission was considered essential to enable the orbiting
telescope to continue to operate.

Posted by flow Frazao on February 20, 2004 at 03:43 PM | Permalink