Hanging
in the balance
analyzing the data, both teams reported
in 1998 that the universe’s expansion
isn’t just cruising along — it is accelerating. Some mysterious force, now known
as dark energy (see Page 24), is driving
space apart, faster and faster.
By Elizabeth Quill s Illustration by Nicolle Rager Fuller
The fate of the universe was sup- posed to be sealed by the turn of the millennium.
“I imagined we’d be walking around
holding a sign saying ‘the world is coming to an end’ or ‘the world is not coming
to an end,’” recalls astrophysicist Saul
Perlmutter.
But as Y2K soothsayers readied for
impending doom, Perlmutter and his
colleagues delivered a surprising dis-
covery suggesting that the world’s
fate would stay in limbo long after
the Times Square ball dropped and any
leftover champagne went flat. More than
a decade later, scientists are still vigor-
ously debating what their finding means
not only for the universe’s future, but
also for all of cosmology.
A dark twist
Before dark energy’s discovery, the
forecast was surprisingly simple. If the
gravitational pull of all the matter in
the cosmos was strong enough to rein
in expansion — like the Earth’s pull on
a rocket that can’t quite reach escape
velocity — the universe would eventually
come crashing in on itself. That ending,
dubbed the Big Crunch, would mirror the
Big Bang that started the cosmic expansion in the first place. If, though, the
universe’s expansion escaped the claws
of gravity, it would go on growing forever.
Expansion would slow but never halt,
and instead of ending, the universe would
