Time
is running out - literally, says scientist
By
Tom Chivers and Roger Highfield, Science Editor
http://www.telegraph.co.uk
Scientists have come up with the radical suggestion that the
universe's end may come not with a bang but a standstill -
that time could be literally running out and could, one day,
stop altogether.
Are we
missing a dimension of time?
The idea that time itself could cease to be in billions of
years - and everything will grind to a halt - has been set
out by Professor José Senovilla, Marc Mars and Raül Vera of
the University of the Basque Country, Bilbao, and University
of Salamanca, Spain.
The motivation for this radical end to time itself is to
provide an alternative explanation for "dark energy" - the
mysterious antigravitational force that has been suggested to
explain a cosmic phenomenon that has baffled scientists. A
decade ago, astronomers noticed that distant supernovae -
exploding stars on the very fringes of the universe - seemed
to be moving faster than those nearer to the centre,
suggesting that they were accelerating as they shot through
space.
Dark energy was suggested as a possible means of powering
this acceleration of the expansion of the cosmos.
The problem is that no-one has any idea what dark energy is
or where it comes from, and theoreticians around the world
have been scrambling to find out what it is, or get rid of
it.
The team's proposal, which will be published in the journal
Physical Review D, does away altogether with dark energy.
Instead, Prof Senovilla says, the appearance of acceleration
is caused by time itself gradually slowing down, like a clock
that needs winding.
"We do not say that the expansion of the universe itself is
an illusion," he explains. "What we say it may be an illusion
is the acceleration of this expansion - that is, the
possibility that the expansion is, and has been, increasing
its rate."
Instead, if time gradually slows "but we naively kept using
our equations to derive the changes of the expansion with
respect of 'a standard flow of time', then the simple models
that we have constructed in our paper show that an "effective
accelerated rate of the expansion" takes place."
While the change would be infinitesimally slow from an
ordinary human perspective, from the grand perspective of
cosmology - in which scientists study ancient light from suns
that shone billions of years ago - this temporal slowing
could be easily measured.
Astronomers are able to discern the expansion speed of the
universe using the so-called "red shift" technique.
The principle is the same as that of an ambulance siren which
gets higher as it comes towards the listener but lower as it
moves away. Similarly, a star moving away appears redder in
colour than one moving towards us.
Scientists look for exploding stars - supernovae - of certain
types that provide a benchmark to work against.
However, the accuracy of these measurements depend on time
remaining invariable throughout the universe.
If time is indeed slowing down, so that according to this new
suggestion our solitary time dimension is slowly turning into
a new space dimension, then the far-distant, ancient stars
seen by cosmologists would therefore, from our perspective,
look as though they were accelerating.
"Our calculations show that we would think that the expansion
of the universe is accelerating," says Prof Senovilla.
The group bases its idea on one particular variant of
superstring theory, a so called theory of everything, in
which our universe is confined to the surface of a membrane,
or brane, floating in a higher-dimensional space, known as
the "bulk".
In some number of billions of years, time would cease to be
time altogether - and everything will stop.
"Then everything will be frozen, like a snapshot of one
instant, forever," Prof Senovilla tells New Scientist
magazine. "Our planet will be long gone by then."
However, he adds that the team is only assuming there is one
dimension of time. Itzhak Bars of the University of Southern
California in Los Angeles has put forward the bizarre
suggestion that there are two dimensions of time, not the one
that we are all familiar with.
Prof Senovilla says: "One thing that is definitely not
included in our models is the possibility of having more than
one time dimension."
While the theory is outlandish, it is not without support.
Prof Gary Gibbons, a cosmologist at Cambridge University,
believes the idea has merit.
"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 says.
"The wonderful thing about these explanations is that,
strange as they sound, the Large Hadron Collider could
provide evidence for extra dimensions in the universe,"
comments Dr Brian Cox of Manchester University, referring to
the atom smasher in Geneva that will start up next year.
"If that happens, then these kind of theories will move out
of the realm of speculation and into the mainstream."