Stop the universe, it's leaving us behind

Wave goodbye to the universe.

The expansion of the universe, which began about 15 billon years ago with the Big Bang, is mysteriously getting faster, Australian and British astronomers say.

However, they admitted yesterday they did not have a clue what ``dark energy" was driving the galaxies to defy gravity and fly apart with ever increasing speed.

``We don't understand the physical process," said Matthew Colless, of the Australian National University.

But, ``eventually the universe will accelerate so rapidly the more distant galaxies we can see today will move away faster than the speed of light and will disappear over the horizon."

Expansion faster than light is possible because, not only are galaxies flying apart at extraordinary speeds, but space itself is expanding, carrying the galaxies away with it.

Until 1998 astrophysicists were debating whether gravity was slowing the expansion enough to eventually cause the universe to collapse in a Big Crunch.

That year other astronomers, including Brian Schmidt, of the ANU's Mount Stromlo Observatory, near Canberra, produced the first solid evidence that the expansion was accelerating.

Studying exploding stars, they found that the more distant ones were fainter and thus further than seemed possible. They concluded an accelerating universe was to blame.

``It was a huge surprise," Dr Schmidt recalled yesterday. ``I was rather scared to go out and tell people. I thought they'd laugh me off the planet."

Dr Colless, one of the first he told, was ``shaking his head".

The new project, involving the ANU, the University of NSW, the Anglo-Australian Observatory near Coonabarabran, and British scientists, led by Cambridge Professor George Efstathiou, used a different method to reach the same finding.

They spent five years mapping the position and speed of 220,000 galaxies. They then compared the data with microwave radio charts of other scientists to ``map" the universe as it was 150,000 years after the Big Bang before the first galaxies even lit up. They found that only an accelerating universe would have allowed it to grow to today's size.

``Now we have two independent pieces of evidence that both give exactly the same answer," Dr Colless said. ``I didn't believe Brian at first ... you have to rearrange the mental furniture."

While most galaxies would vanish from view, the Milky Way, and its nearest neighbours, glued together by gravity, would travel on alone. Dr Schmidt said the confirmation was ``great news for me. I can sleep a little better. It's evidence we didn't screw up four years ago."