Jeff Forshaw's talk – a write-up

On Monday 12th September (SciBar’s seond birthday) Jeff Forshaw led the Bollington SciBar in a discussion of “Our natural world – or why physics is so interesting”. Jeff, Professor of Theoretical Physics at the University of Manchester, provided a taster of his forthcoming book with TV presenter and fellow Manchester physicist Brian Cox called “The Quantum Universe”. Brian and Jeff are long-time collaborators, and Jeff served as series consultant on the BBC “Wonders of the Universe” series.

Quantum physics is one of the weirdest things to come out of 20th-century physics. To illustrate this, Jeff explained that a point-like particle can be simultaneously at many different points, and to travel from place to another there are an infinity of possible paths it can take. Every component in a grain of sand is jumping everywhere in the Universe. However there is a number associated with each of these possibilities and when the numbers associated with all possibilities are added up some parts of the sum cancel each other out.  The chances of the sand grain leaping away are miniscule.

Yet, as Jeff explained, quantum theory is both necessary and useful. It is the key to understanding everything in the physical world. Quantum physics is also of enormous technological importance: the transistors that underpin the computer age were made possible by the quantum theory of materials called semiconductors.

Like Brian Cox, Jeff is working on the world’s most powerful particle experiment, the Large Hadron Collider (LHC). The LHC accelerates a beam of charged particles to near the speed of light, to collide them at very high energies. The LHC makes 100 million collisions per second, each collision creating thousands of new particles, which may themselves combine. Jeff’s role is to calculate the mathematical probability that certain particles will be formed, and where these particles will end up. Crucially, his calculations show that a few thousand ‘Higgs particles’ should have been created since the LHC was switched on. However, searching for evidence of these particles will not be easy, with millions of other events detected each second. Jeff’s view is that physicists will wait until they have several thousand Higgs detections before announcing they have found it. He likened this to Rolf Harris asking of his part-completed picture: “Can you see what it is yet?”

While the great physicist Richard Feynman famously said: “I think I can safely say that nobody understands quantum mechanics”, Jeff answered the audience’s ongoing queries (“My brain hurts – can you just explain …”) with skill and humour. There was a lively question and answer session to finish (and even some equations on scrap paper afterwards, for the truly dedicated).

Many thanks to Professor Forshaw for an entertaining and informative talk, and to one of our SciBar regulars Jon Thompson for acting as chair for the evening. It was his birthday too!

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