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SCIENTISTS claim they have broken the ultimate
speed barrier: the speed of light.
In research carried out in the United States, particle
physicists have shown that light pulses can be accelerated to up to 300
times their normal velocity of 186,000 miles per second. The implications, like the speed, are mind-boggling. On
one interpretation it means that light will arrive at its destination
almost before it has started its journey. In effect, it is leaping forward
in time.
Exact details of the findings remain confidential
because they have been submitted to Nature, the international scientific
journal, for review prior to possible publication.
The work was carried out by Dr Lijun Wang, of the NEC
research institute in Princeton, who transmitted a pulse of light towards
a chamber filled with specially treated caesium gas. Before the pulse had fully entered the chamber it had
gone right through it and travelled a further 60ft across the laboratory.
In effect it existed in two places at once, a phenomenon that Wang
explains by saying it travelled 300 times faster than light.
The research is already causing controversy among
physicists. What bothers them is that if light could travel forward in
time it could carry information. This would breach one of the basic
principles in physics - causality, which says that a cause must come
before an effect. It would also shatter Einstein's theory of relativity
since it depends in part on the speed of light being unbreachable.
This weekend Wang said he could not give details but
confirmed: "Our light pulses did indeed travel faster than the
accepted speed of light. I hope it will give us a much better
understanding of the nature of light and how it behaves."
Dr Raymond Chiao, professor of physics at the University
of California at Berkeley, who is familiar with Wang's work, said he was impressed by
the findings. "This is a fascinating experiment," he said.
In Italy, another group of physicists has also succeeded
in breaking the light speed barrier. In a newly published paper,
physicists at the Italian National Research Council described how they
propagated microwaves at 25% above normal light speed. The group
speculates that it could be possible to transmit information faster than
light.
Dr Guenter Nimtz, of Cologne University, an expert in
the field, agrees. He believes that information can be sent faster than
light and last week gave a paper describing how it could be done to a
conference in Edinburgh. He believes, however, that this will not breach
the principle of causality because the time taken to interpret the signal
would fritter away all the savings. "The most likely application for this is not in
time travel but in speeding up the way signals move through computer
circuits," he said.
Wang's experiment is the latest and possibly the most
important evidence that the physical world may not operate according to
any of the accepted conventions. In the new world that modern science is beginning to
perceive, sub-atomic particles can apparently exist in two places at the
same time - making no distinction between space and time.
Separate experiments carried out by Chiao illustrate
this. He showed that in certain circumstances photons - the particles of
which light is made - could apparently jump between two points separated
by a barrier in what appears to be zero time. The process, known as
tunnelling, has been used to make some of the most sensitive electron
microscopes.
The implications of Wang's experiments will arouse
fierce debate. Many will question whether his work can be interpreted as
proving that light can exceed its normal speed - suggesting that another
mechanism may be at work. Neil Turok, professor of mathematical physics at
Cambridge University, said he awaited the details with interest, but
added: "I doubt this will change our view of the fundamental laws of
physics."
Wang emphasizes that his experiments are relevant only
to light and may not apply to other physical entities. But scientists are
beginning to accept that man may eventually exploit some of these
characteristics for inter-stellar space travel. |
UNITED STATES