Published: 02.21.2004
By James Glanz
THE NEW YORK TIMES
MARINA DEL REY, Calif. - A dark, unseen energy is steadily pushing the universe
apart just as Einstein once predicted, suggesting the universe may have a more
peaceful end than more recent theories envisioned, according to new measurements
of distant exploding stars by the Hubble Space Telescope.
The energy, whose source remains unknown, was named the cosmological constant
by Einstein. In a 1917 prediction he later called "my greatest blunder,"
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 - tens of billions of years from now.
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."
On Friday, Adam Riess of the Space Telescope Science Institute in Baltimore
presented the first broad set of observational data that gauges the strength
of the antigravity force over time. The data, he says, suggest the cosmos will
gradually expand, cool and darken, more akin to a slide into senescence rather
than a violent apocalypse.
Riess and his team, which included Louis Strolger of the science institute and
Alexei Filippenko of the University of California-Berkeley, used the Hubble
to search for exploding stars, or supernovas, which are swept up in the dark
energy's cosmic push. They discovered 42 supernovas in their survey area, including
six of the seven most distant known.
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 semipermanent kind of dark energy,"
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," Riess said, "is looking a lot better than
before this data."