COLLIDER by Paul Halpern

This inauspicious-looking object is actually the portal to a new world. It takes high frequency sound and makes it audible to humans. Last night Hodmandod Senior and I took a walk - and for much of the time there was just a steady hum. We went where we thought there would be bats - in a dark country lane with overhead trees - but apart from the odd rustle, it was quiet. Then, along a more suburban street we suddenly heard it: a clack, clack, clack - loud and sharp - the sound of a bat's sonar.

We stood still, Hodmandod Senior pointing the detector in different directions, its weak beam of light illuminating nothing much except the branches of trees and the poles of street lights, but the sound of the bat was there, swooping around, changing speed and intensity. We had suddenly become aware of something that had been there all along: an inaudible world made audible. Or the fragments of another universe slipping through into the one that I know.

This sounds like science-fiction but it is not. As I learnt in one of the last chapters of Paul Halpern's fascinating book Collider, this is exactly what they are trying to do in the Large Hadron Collider (LHC) near Geneva in Switzerland. In one of the ideas about our universe ('the Braneworld Hypothesis') all the tiny, subatomic particles and components that make up our own universe are thought of as strings. Most of these strings have sticky ends, and these prevent them from passing through the membrane (brane is short for membrane) of our 3D-universe and into any other of a different dimension. However gravitons, which are the components of gravity, are different. Graviton strings try to swallow their own tails and are shaped like doughnuts. They are therefore non-sticky and therefore free to slip through from universe to universe. The LHC operates at just the right energy to detect these theoretical particles so if it detected them, like I detected the bat last night, then this might be evidence for this 'Braneworld Hypothesis.' If there is evidence for other universes of extra dimensions then this could help astronomers understand dark matter. Dark matter is thought to make up 23% of our universe, the bulk of the rest is dark energy (73%), leaving just 4% that is 'luminous' or the stuff we can see.

However, as Paul Halpern explains, detection of something like a graviton in the LHC is not likely to be a simple thing like a bat-clack, or a flash of a light on a fluorescent screen, but the result of months of data analysis. Evidence of the existence of gravitons will be elusive; maybe more like searching for the voice of a bat in a cacophony of other night-sounds.

The idea that our universe is just one of many existing alongside each other is just one of the amazing ideas towards the end of this book. The LHC - which will not cause a black hole, not a destructive one at any rate (as chapter 11 starts 'Not all scientists are lunatics') - has many functions, but perhaps the most famous one is to search for the Higgs Boson.

Paul Halpern explains why finding the Higgs Boson is so important. It would be further evidence that the universe started with a big bang. Just as we all carry remnants of our ancient ancestry from, say, unicellular creatures, in the genes of our DNA, so atoms are thought to carry remnants of the start of the universe in their subatomic components. The Higgs Boson is one of these components, and the only way scientists will be able to find it is by smashing already tiny particles (protons) against each other at the highest energy they can muster; that is accelerating the particles until they are moving at close to the speed of light.

I have often found it remarkable that in order to explain the existence of the largest thing that we can imagine we have to search for the smallest thing too. It is another mouth swallowing its tail, and we seem to be stuck in the middle searching around for an end and a way in. For the curious lay-reader the field is perplexing and complicated, but luckily there are guides like Paul Halpern around that can tell us about these ideas in a clear way.

Gradually, he builds up a picture of the search for the world's smallest particles, starting from the ancient world through the modern world of atoms that is part of every High school curriculum, and then, from the 1950s, the more specialised world of recent mind-boggling ideas of quarks, fermions, bosons, leptons, hadrons, pions, gluons and various sorts of weak forces: 'a zoo of particles with bizarre properties and a wide range of lifetimes'. Even the most general reader builds up an impression of spins that don't actually 'spin', light and theories that are difficult to marry together, and how gravity is a misfit.

Along the way there are fascinating anecdotes of scientists and facts: scientists like Dirac who made important discoveries about the pieces of the puzzle and yet were unable to fit in themselves; calamitous stories of fixing lightning rods to Alpine peaks and then pertinent quotes from authors such as Voltaire and Plato.

Eventually, of course, it leads to the story of the Hadron Collider and story of making something small go fast... and the collision, and the detection, and the fight for funds. In this section too there are interesting facts and characters that really bring the story to life: the story of Robert (Bob) Wilson that was responsible for the Fermilab, and its modernistic and award-winning architecture covering dirt-floors, and the scientists who were working there - on one of the pinnacles of human achievement - having to wade through puddles to take their measurements.

I found Collider a compelling and invigorating read, and one that I am sure will change the way I think about the universe and my place within it. It has shown me that there are many ways of observing, and it is only by questioning what we think we perceive that we can learn where we have come from and where we are going. From now on I think I will listen to the bat clicks in the dark with a new concentration.