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Welcome to Double Helix magazine’s Q&A section – Microscope. We take a close look at small questions full of big ideas.

Q: I would like to know how a Higgs boson gives other particles their mass?
The Helix reader, Michael from Queensland

 
In 2012, physicists working on one of the world’s largest scientific devices reported extraordinary news – they had identified something that behaved just as a certain hypothetical particle would behave. Called the Higgs boson, this particle had been predicted to exist by a model of physics for more than half a century.

To understand what this particle does, it helps to know what a boson is. You probably already know that matter is made up of atoms. There’s a good chance you also know that atoms have a nucleus and are usually surrounded by one or more electrons. Electrons aren’t made up of smaller things, so we can say they’re fundamental particles.

The nucleus, however, can be broken into protons and neutrons. In turn, these are made up of something even smaller – quarks. As far as anybody can tell, quarks are also fundamental particles.

To describe a particle, scientists say it has properties. These include measurements such as charge, as well as a property called spin. Bosons have one particular sort of spin. Other particles – called fermions – have another type. Among other things, spin determines whether particles can move through one another like ghosts, or stick to their own space like solid objects.

As such, you can think of atoms being made of bits that can’t occupy the same space (fermions), and particles that zip about at light speed, informing other particles how to behave (bosons).

Quarks are fermions – they give protons and neutrons their volume. Bosons called gluons zip between the quarks in a proton, informing them they are attracted to each other, so they don’t fly apart. Photons of light are also bosons. They carry information that produces electricity and magnetism.

So, what is mass? Mass is a measure of how easy it is to move, stop or steer a particle. It takes more energy to accelerate a heavy particle to a given speed. Some particles have no mass and they always travel at the speed of light – they can’t go slower.

In the 1950s, a number of physicists – including one by the name of Peter Higgs – figured some sort of boson had to be responsible for carrying the information that gives some particles mass. It took a while to find, but as Peter Higgs’ boson has been spotted, we can be even more confident that our ideas about particles are fairly accurate.

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