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THE mysterious "dark
energy" that is pushing apart the universe appears to be the
constant force that Albert Einstein once predicted, according
to measurements made by the Hubble Space Telescope.
NASA scientists announced
their findings Friday, and details are to appear in an
upcoming issue of Astrophysical Journal.
The force is an unknown form
of energy that behaves in an opposite manner from the pull of
gravity. Dark energy causes the galaxies within the universe
to move apart from one another at ever-increasing speeds.
Einstein called the force
the "cosmological constant." He theorized its existence to
balance the universe against normal gravity and keep it from
collapsing on itself.
Einstein ultimately
dismissed the theory as his greatest blunder, but subsequent
observations of supernovas, or distant stars that exploded
long ago, gave it credence. Scientists now know dark energy
causes the universe to expand and accelerate. It makes up an
estimated 70 percent of the universe. What was unclear is
whether dark energy is stable.
If it grows stronger with
time, the universe could end with galaxies, stars, planets
and, ultimately, atoms coming unglued in a violent expansion
that theorists call the "big rip." In the alternative, dark
energy could fade away to the point where it flipped in force,
pulling the universe back together in what's called the "big
crunch."
The latest Hubble
observations announced suggest dark energy is unwavering, just
as Einstein predicted. "Right now, we're about twice as
confident than before that Einstein's cosmological constant is
real, or at least dark energy does not appear to be changing
fast enough - if at all - to cause an end to the universe
anytime soon," said Adam Riess, of the Space Telescope Science
Institute in Baltimore, which looks at data sent from the
Hubble.
Even if Einstein was wrong,
dark energy won't spell an end to the universe for at least
another 30 billion years, scientists said. The latest results
come from the measurements of multiple supernovas that
exploded when the universe was half its present age of nearly
14 billion years.
The apparent brightness of a
certain type of supernova allows scientists to gauge the
expansion rate of the universe at different times in the past.
That in turn allows them to measure any change in the strength
of the force exerted by dark energy. Further research is
needed to prove dark energy is indeed a constant force,
scientists said.
However, NASA's decision to
no longer repair Hubble means the work will be interrupted
until a replacement can be built and launched.
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