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Now that physicists at the Large Hadron Collider at Cern have found a Higgs particle, are they reaching the end of the road? Their observations have finally revealed a quantum manifestation of the Higgs field, which imbues matter with inertia, and can distinguish between particles that have mass and those that don't. The bigger the mass of a particle, the larger its inertia and the greater its interaction with the Higgs field.

Of course there are still a few loose ends. The graviton, a stable quantum realisation of the gravitational field, has not yet been seen, nor the newly proposed Wang particle, an unstable entity of similar ilk, to say nothing of other possible Higgs particles. The idea — and it's a grand one — is that all these particles fit in with the Standard Model, which describes the three quantum forces of nature: electromagnetism, the weak nuclear force, and the strong nuclear force. Along with gravity this makes four forces that are supposed to be the basis for everything, but if this is the end of particle physics, let us examine how we got to this point.

Questions about the fundamental constituents of matter have been around for a very long time. The Greeks had four basic elements: earth, fire, air and water, and many of their ideas came from the Babylonians who had similar notions, while the ancient Chinese had five, including wood and metal, but excluding air. Why four or five? The reason could be related to the natural division into four cardinal directions, shared by all cultures. The Chinese even thought of the earth as square, surrounded on its four sides by four great oceans. They also imagined a fifth cardinal direction for heaven, and the Greeks adopted five elements when they included the aether, that "ethereal" substance that no one could see or feel, which in Latin became the quinta essentia or quintessence.

Yet despite this standard model of the cosmos, there were Greeks such as Democritus who wanted to explain things in terms of more elementary constituents called atoms. This word comes from the Greek atomos meaning uncuttable, in other words indivisible, and in the 19th century we found them, in profusion. Atoms of gold, atoms of iron, copper, hydrogen, oxygen, and so on, finally quashing the dream of the alchemists that base metals could be turned to gold. No chemical process could do this because no amount of clever alchemy could convert an atom of one type into one of another type.

Then in 1897, J.J. Thomson at Cambridge discovered negatively charged electrons, which he realised were tiny constituents of atoms. The atoms themselves had no charge, so the electrons had to be moving in a positively charged environment, which led to the "plum pudding model" of the atom with electrons like tiny pieces of fruit whirling around in a positively charged pudding. Twelve years later in 1909 one of Thomson's students, Ernest Rutherford, showed that the positive charge lay entirely in a tiny nucleus, and then the nucleus too started to reveal constituents of its own: positively charged protons, and electrically neutral particles called neutrons discovered by James Chadwick, who at one time worked under Rutherford.

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