Then there was light

Many of the most fundamental phenomena in physics are related in some way or other to light and its properties. This has been the theme of the book. We concluded with Einstein's theory of special relativity, which on the basis of the universal constancy of the speed of light, leads to the equivalence of matter and energy. When Einstein derived his famous equation in his 'laboratory of the mind', he could hardly have imagined that within half a century it would be possible to build machines which could turn energy into matter at the precise rate of exchange which he had predicted.

When it became possible to create matter at particle accelerators, a window opened into a new world. Myriads of new fundamental particles were discovered. The exploration of the physical laws governing this microscopic, sub-nuclear world became a major and exciting goal. Experimental physicists from many countries pooled their skills and funding to build experiments of unprecedented size and complexity, driving themselves to the very edge of technological feasibility.

Einstein's words 'The most incomprehensible thing about the world is that it is comprehensible' applied equally to the new world. As theoretical physicists untangled the properties and the interrelations between particles, they found that by logical argument they could predict the existence of hitherto-unobserved particles.

The final chapter of our story of light and its place in the universe concludes with the prediction of the existence of a family of three particles — with masses about 100 times the mass of the proton — which act as the carriers of the weak nuclear force in a similar manner to the function of the light quantum which carries the electromagnetic force. It was a testimony to the high esteem in which the theorists were held when a colliding beam accelerator of unprecedented size and complexity was constructed to look for this heavy light'.

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