Dienstag, 28. Juli 2009
The Day the time went out
Time may literally be running out – and could one day vanish altogether, according to a bizarre new theory.
The suggestion has been put forward to explain a cosmological mystery that has baffled scientists.
A decade ago, measurements of the light from distant exploding stars showed the universe to be expanding at an accelerating rate.
Physicists assumed that a kind of anti-gravitational force must be driving the galaxies apart, and gave it the name “dark energy”.
However, to this day no-one has been able to say what dark energy is or where it comes from.
The new theory from Professor Jose Senovilla, at the University of the Basque Country in Bilbao, Spain, offers a radical alternative idea.
He believes there is no such thing as dark energy. Instead, he says we have been fooled into thinking the expansion of the universe is accelerating because time itself is slowing down.
At our local everyday level, the change would be imperceptible.
But it would be obvious from cosmic scale measurements tracking the course of the universe over billions of years.
Astronomers work out the speed of the universe’s expansion from the frequency of light emitted by certain types of supernovae, or exploding stars.
However, these measurements depend on our current perception of time, says Prof Senovilla.
If time has been slowing down, and clocks are now running more slowly than they did long ago, it would appear from our perspective as if things have been speeding up. Looking back over billions of years, galaxies would seem to be travelling away from each other faster and faster at various intervals since the Big Bang.
“Our calculations show that we would think that the expansion of the universe is accelerating,” said Senovilla.
His idea is based on string theory concepts which allow dimensions of space and time to switch from one to another.
If our single time dimension was changing into a new space dimension, it would produce just such an effect.
After billions of years, time would eventually disappear altogether.
“Then everything will be frozen, like a snapshot of one instant, forever,” Prof Senovilla told New Scientist magazine. “Our planet will be long gone by then.”
Prof Gary Gibbons, a cosmologist at Cambridge University, is drawn to the idea.
“We believe that time emerged during the Big Bang, and if time can emerge, it can also disappear – that’s just the reverse effect,” he said.