THEORETICAL physicists have long asked themselves why matter has mass, since at the moment of the Big Bang, there was no mass.

Professor Higgs proposed that a minute fraction of a second after the Big Bang, a field switched on throughout the universe.

This interacted with all the newly created particles, slowing them down from the speed of light and hence giving them mass - the Higgs field.

One analogy to explain how the Higgs Field works is given by Professor David Miller, emeritus professor of physics at University College London, who likens it to a gathering of political party workers.

When a senior politician enters, nearby activists cluster around her, slowing her down as she crosses the room - giving her mass.

So the field becomes locally distorted when a particle - politician - moves through it.

Here and there are individuals who have no interest in the politician and pass straight through the "field" at a steady pace: they are massless particles.

So why the Higgs boson? Isn't that a particle? Mr Miller describes a rumour passing through the room.

The rumour is passed from one activist to another, forming a wave of clustering throughout the room.

These clusters also have mass.

The Higgs boson is thought to be a clustering of this sort in the Higgs field.

Generating the boson - by smashing particles together in the Large Hadron Collider - proved the existence of the field. The theory is punishingly complicated - which is why Mr Higgs got a Nobel Prize for it.