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Twenty-four-hour particle people: the ongoing reinvention of particle physics

The Large Hadron Collider, the machine that smashed particles together to create the Higgs boson, is closed for an upgrade and will next host particle collisions in 2015. Yet there is hope of further insight before then.

A scientist walks inside a tunnel at the Large Hadron Collider. Photo: Fabrice Coffrini/AFP/Getty.

You might have thought that 2014 would be a restful year in theoretical physics. In December, Peter Higgs received his Nobel Prize. Surely all the fuss over the Higgs boson, which was discovered in July 2012, 48 years after Higgs predicted its existence, has finally run its course? Not at all: physicists are already scheming about what comes next.

This month, some of the subject’s leading lights gathered at the Higgs Centre in Edinburgh to divine the future of physics. It’s an important discussion because Higgs’s boson hasn’t given them many clues.

We know that there must be many more bosons out there, because we have yet to find a way to mesh quantum theory, our mathematical description of reality at the smallest scales, with relativity, which describes the reality of space and time on the scale of galaxies. There are plenty of theories but there is still little data to guide discussions.

The Large Hadron Collider (LHC), the machine that smashed particles together to create the Higgs boson, is closed for an upgrade and will next host particle collisions in 2015. Yet there is hope of further insight before then.

In December, a team of US researchers identified more than 100,000 ways in which current data might show us as yet unseen physics. The way the Higgs boson “decayed” – or changed into other particles and energy configurations after its creation – might have deviated from the expected routes. Finding out if it did take one of the 100,000 unexpected turns will require sifting through 100 petabytes of data. In comparison, storing every word ever written by human beings would require about 50 petabytes of data.

If that doesn’t show the Higgs doing something interesting, we’ll have to wait for the Advanced LIGO project to start operating later this year. This is designed to detect gravitational waves – ripples in space – caused by cataclysmic events such as the collision and merger of two black holes. Einstein predicted gravitational waves should exist but we have yet to see one. Advanced LIGO can detect the tiniest wobbles in space: if a black hole merger causes the planet to move half an atom’s width closer to the sun, we’ll know about it.

If we do snag a gravitational wave, analysing its properties should reveal details of where quantum theory and relativity meet. We already have data on that coming in: the European Space Agency’s Planck satellite is sampling the cosmic microwave background radiation that was produced shortly after the Big Bang and contains information about how quantum effects seeded the structure of galaxies. Results from this mission are enabling us to rule out certain theories about what happened in the earliest moments of the universe, providing another avenue for exploring the most fundamental rules governing the cosmos.

The LHC will resurface next year – but it is small that may prove beautiful in the end. In Edinburgh, Birmingham University’s Andrew Schofield introduced theorists to the prospect of particle physics done on a tabletop. There are many types of solid material that have properties analogous to large colliders – if you manipulate them correctly, you can make energy ricochet through the material in ways that mimic the flight and interactions of free-flying protons in kilometre-long particle accelerators. This may not be as awe-inducing as the big machines but we’ll take insights wherever we can get them.