From the 1993 lecture programme:
100 metres below ground, among the ﬁelds north of Geneva, is the world’s largest scientiﬁc instrument —— the LEP (for Large Electron Positron collider). Beams of electrons and their antimatter counterparts — positrons — whirl around a 27km racetrack at near to the speed of light. Suddenly they smash head on into each other producing in a small volume the hottest place on Earth, hotter even than the centre of the Sun and hotter perhaps than anywhere in the Universe since the original Big Bang.
When matter and antimatter meet they may mutually annihilate and turn into a ﬁreball of radiation -— Space travellers to anti-galaxies beware! Antimatter sounds like the stuff of science ﬁction, but it is a very real part of the Universe. Although all bulk material is made of matter, (good news for future astronauts) individual pieces of antimatter arrive in cosmic rays and we can now produce large quantities for use in experiments. Antimatter is even used as a medical diagnostic.
Collisions between matter and antimatter happened everywhere in the first fractions of a second of the Big Bang. By reproducing these conditions at LEP we can learn how the material ingredients of the Universe were formed and discover the fundamental modus operandi of nature. In order to capture the images of these cataclysmic collisions, LEP contains four huge particle detectors. Each is bigger than a two storey house and weighs more than ﬁve jumbo jets; their surroundings look like something from the imagination of H.G. Wells and their sophisticated electronics produce fantastic visions. In this lecture we will visit LEP and go deep underground to see the experiment for ourselves.