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Mystery of the Sun's particles
that go missing

Sun Cartoon

Robert Matthews

In 1967,an American scientist named Raymond Davies descended into the Homestake Gold Mine in South Dakota,filled a huge metal tank with 140 tons of industrial cleaning fluid - and waited.He was looking for signs of ghostly sub - atomic particles called neutrinos hitting the chlorine atoms in the cleaning fluid and turning them into atoms of the inert gas argon

Davis's interest in these esoteric particles had been sparked by the work of astronomers on unravelling the nuclear fusion reactions that are the power source of the Sun.Neutrinos were expected to be a by-product of these reactions,and as such could give Davis the first direct insights of conditions at the core of our nearest star.

As the months went by,the neutrinos duly arrived although not at the rate Davis expected.At first,it seemed that the dearth of neutrinos might have been the result of not waiting long enough,or some quirk of the experiment.But as the months turned into years and the years into decades,the neutrinos still refused to arrive at the expected rate.

Today,the Homestake experiment is still running,and has been joined by many others around the world.And they all find broadly the same result: there is a 30 to 50 per cent shortfall in the number of neutrinos coming from the Sun.

Theorists have come up with a range of theories to explain the anomaly.Some lay the blame at the door of the Sun - that for some reason,its core is cooler than expected,and so churning out fewer neutrinos.

One worrying suggestion is that the Sun's internal reactions have actually stopped.As light from the inner regions of the Sun bounces around many times inside it before reaching the surface,we would have no inkling of this for millions of years.

Other,less dramatic - and more plausible - explanations point the finger at the particles themselves,suggesting that they get up to some monkey business on the journey from the Sun to Earth.

Now a team of Polish physicists have come up with the most radical theory yet: that some of the neutrinos are breaking one of the golden rules of physics and are travelling faster than light.

Einstein's theory of relativity does not,in fact,prohibit faster-than-light travel: only particles accelerating from a standing start to "superluminal" speeds.If,however,a particle is born already travelling faster than light,Einstein would have no problems with it.

This is what Jakub Rembielinski and his colleagues at Lodz University are now proposing for neutrinos.One bizarre consequence of their proposal is that neutrinos would no longer have mass in the conventional sense.Instead,they have something called "imaginary" mass,a variety of mass that is in some sense at right angles to the ordinary kind.

Fortunately,while human intuition fails completely when faced with such ideas, mathematics does not,and Rembielinski has been able to calculate some of the implications of neutrinos possessing imaginary mass.

One of them is that some types of neutrinos would become unstable,decaying into other types that could evade detection by experiments like those in South Dakota. According to New Scientist,the type of decay predicted could account more or less exactly for the "missing" neutrinos.

The explanation comes with a hefty price-tag,however - in the form of some odd consequences of superluminal travel.Most serious is the problem of particles actually travelling backwards in time,reversing cause and effect.

Whether the scientific community can accept such possibilities in return for solving the mystery of the missing neutrinos is as yet unclear.What is clear, however,is that the suggestion is eerily similar to a description that appears in the works of the First Century BC Roman poet and philosopher Lucretius.

In his epic poem De rerum natura - "On the nature of things" - he describes the nature of particles that come from the "inmost depth" of the Sun."Surely," says Lucretius,"they must go all the faster and the farther and traverse an extent of space many times as great in the time it takes for the sunlight to flash across the sky?"

Only a little poetic licence is needed to see this as a virtually perfect description of faster-than-light neutrinos from the solar core.A coincidence? Perhaps.But then again,perhaps the spooky prescience of Lucretius is evidence for the existence of superluminal particles that can travel back in time.






Sunday Telegraph File Info: Created --/--/-- Updated 25/8/2003 Page Address: