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Page last updated at 06:01 GMT, Tuesday, 9 September 2008 07:01 UK
On the hunt for the Higgs boson

Stephen Hawking in his study
Hawking’s books have made him a world-renowned theoretical physicist
The sum of human knowledge could be massively increased on Wednesday - but Professor Stephen Hawking could find himself $100 poorer.

As Cern prepares to switch on the Large Hadron Collider (LHC) below the French-Swiss border, the physicist has a bet that it will not find the Higgs boson - the most highly sought-after particle in physics.

Dubbed the "God particle" because it is so crucial to our understanding of the Universe, it is thought to give everything its mass.

The most powerful physics experiment ever built, the LHC will re-create the conditions present in the Universe just after the Big Bang.

When subatomic particles like protons are smashed together in the LHC, the energies released will create an array of new particles - some of which have not been seen since the big bang itself. It will give scientists a glimpse into how these building blocks of matter are made.
Both the LHC, and the space programme, are vital if the human race is not to stultify, and eventually die out

"The LHC will increase the energy at which we can study particle interactions, by a factor of four. According to present thinking, this should be enough to discover the Higgs particle, the particle that gives mass to all the other particles," Professor Hawking told the Today programme.

Previous particle accelerators have failed to find it, but because the LHC is so much more powerful, there is hope that it will succeed. Even a failure, Professor Hawking says, would be exciting, because that would pose new questions about the laws of nature.

"I think it will be much more exciting if we don't find the Higgs. That will show something is wrong, and we need to think again. I have a bet of $100 that we won't find the Higgs."

He believes another important discovery that the experiment could make is superpartners, or particles that should theoretically exist. They are "supersymmetric partners" to those particles we already know of at present.

"Their existence would be a key confirmation of string theory, and they could make up the mysterious dark matter that holds galaxies together. Whatever the LHC finds, or fails to find, the results will tell us a lot about the structure of the Universe," he says.
The magnet core of the world's largest superconducting solenoid magnet at Cern
The CMS detector will search for the Higgs boson

Some fear the experiment may create a black hole that will tear the Earth apart - there have even been two last-minute legal attempts to stop it - but Professor Hawking dismisses the idea that the LHC is in any way dangerous.

"If the collisions in the LHC produced a micro black hole, and this is unlikely, it would just evaporate away again, producing a characteristic pattern of particles. Collisions at these and greater energies occur millions of times a day in the Earth's atmosphere, and nothing terrible happens."

Parallel universe?

The human race is characterised by an insatiable quest to understand things, and the LHC is an example of our willingness to invest in that quest.

It is however difficult to predict whether it will bring any practical advances in the scale of our lifetime. But the LHC might reveal something completely unexpected about the workings of our Universe, and that, says Professor Hawking, is what makes physics so satisfying.

"Throughout history, people have studied pure science from a desire to understand the Universe, rather than for practical applications, or commercial gain. But their discoveries have later turned out to have great practical benefits.

"It is difficult to see an economic return from research at the LHC, but that doesn't mean there won't be any."

Asked if he would be able to choose whether the LHC or the space programme is more important in advancing our knowledge of the Universe, Professor Hawking says that would be like "asking which of my children I would choose to sacrifice".

"Both the LHC, and the space programme, are vital if the human race is not to stultify, and eventually die out. Together they cost less than one tenth of a percent of world GDP. If the human race cannot afford that, it doesn't deserve the epithet, human," he added.

Scientists have spoken, if cautiously, of the experiments at Cern venturing into realms long regarded as those of speculative science fiction - multiple universes, parallel worlds, black holes in space linking different levels of existence.
Simulated production of a black hole in Atlas (Cern)
If a black hole is produced, it might look like this in LHC data

Professor Hawking says that a parallel universe may be a universe very different to the one we recognise.

"According to the sum over histories idea of Richard Feynman, the Universe doesn't just have a single history, as one might think, but it has every possible history, each with its own weight. A few of the histories will contain creatures like me, doing different things, but the vast majority of histories will be very different."

In 1974 Professor Hawking argued that due to quantum effects, primordial black holes created during the Big Bang could "evaporate" by a theoretical process now referred to as Hawking Radiation in which particles of matter would be emitted.

Under this theory, the smaller the size of the micro black hole, the faster the evaporation rate, resulting in a sudden burst of particles as the micro black hole suddenly explodes.

In the past Professor Hawking has joked that if the LHC does creates micro black holes - even if they are rather short-lived ones - it could win him the Nobel prize. However, he now says he does not believe this is something that is imminent.

"If the LHC were to produce little black holes, I don't think there's any doubt I would get a Nobel prize, if they showed the properties I predict. However, I think the probability that the LHC has enough energy to create black holes, is less than 1%, so I'm not holding my breath."

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