Question: what gives something its mass?

Ben Smart answered on 12 Mar 2012:

We don’t know for sure, but we think it’s something we call ‘The Higgs Mechanism’. The Higgs Mechanism says that there is a field (like a magnetic or electric field), called the Higgs field, that is everywhere. This Higgs field can do things to some stuff (just like a magnetic field can make iron filings move), and what it does is give things mass.
There are other things (like light) that the Higgs field can’t do anything to, and so these things don’t have mass (just like a magnetic field can’t make a piece of aluminium move).

The word we use to describe this is ‘interaction’. We say that the Higgs field ‘interacts’ with matter, and so gives that matter mass. The Higgs field can’t ‘interact’ with light, and so light has no mass. Mass is really just the effect we see from things interacting with the Higgs field.

If the Higgs Mechanism is real, then there will be a particle (called the Higgs Boson) that no one has ever seen before. At CERN we’re looking for the Higgs Boson, because if we can prove that it exists, then we can be fairly certain that the Higgs Mechanism is real.