In the minds of many, the name ‘Large Hadron Collider’ is linked with the words ‘Higgs Boson’. And so it should be – one of the aims of the LHC is to find (or not to find) this mysterious particle. But what is the Higgs boson?
It’s to do with mass. In broad terms, mass is a measure of how much matter (or ‘stuff’) there is in something. In the everyday world, it is possessed by protons and neutrons, with a small contribution from electrons. In physics, there are really two things that mass does – first, it provides inertia, meaning the more mass something has, the harder it is to get it moving (and the harder it is to stop it once it is moving); secondly, it interacts with a gravitational field (massive things are heavy). Just how or why these two roles are linked is one of the unsolved mysteries of physics.
Peter Higgs’ (amongst others) suggested a theory of the origin of mass in 1964. Essentially, the idea is that something with lots of mass interacts strongly with particles called Higg’s bosons. Something with a small amount of mass interacts only weakly.
Here’s an analogy. If I go for a walk on my own, I’ll go pretty quickly . But if I go for a walk with my niece, it is painfully slow. Not because she walks slowly, but because she’ll stop every five metres to investigate whatever leaf, signpost, cat or beetle happens to be lying in her path. She interacts with the environment much more strongly that I – consequently she moves more slowly through it. Likewise, something with lots of mass interacts strongly with Higg’s bosons; something with little mass interacts only weakly.
So although the Higgs boson is associated with mass, it would be wrong to say that something with lots of mass contains lots of Higgs bosons.
Finally, what’s a boson? This is a tricky one to define in everyday language – it’s to do with how much ‘spin’ a particle has. Spin is one of those nasty little quantum mechanical concepts, and I’m afraid I’ll leave it to another blog entry to try to explain that one. (Or get hold of Jim Al-Khalili’s book ‘Quantum – a guide for the perplexed’.)