At the time, only four types had been seen it must have been very satisfying when the missing quarks were duly discovered, in 1977 and in 1995. In 1973, in another feat of mathematical reasoning, Japanese physicists Makoto Kobayashi and Toshihide Maskawa concluded that the only way to accommodate the deviant results was to suppose that at least six types of quark should exist in nature. In particular, quarks and antiquarks (the particles that are used to build the atomic nucleus) sometimes deviate from perfect symmetry. Matter particles and antimatter particles have, on very rare occasions, been seen to act differently from one other in laboratory experiments. So what spoils the prospect of perfect symmetry between matter and antimatter? Today, particle physics experiments and hospitals (through their use of PET scanners) around the world routinely produce antimatter particles and, in most cases, they behave just as Dirac expected. That "symmetry" between matter and antimatter is the reason why they were created in equal amounts at the birth of the universe and it is why they almost cancelled each other out entirely. According to Dirac's equations, anti-matter should behave exactly like ordinary matter, with the exception that it should carry the opposite electrical charge. Dirac's feat of purely mathematical reasoning was vindicated four years later when Carl Anderson discovered the anti-electron in his laboratory in California. The existence of antimatter was predicted in 1928 by the Nobel-prize winning British physicist Paul Dirac. The message is clear – something must have stepped in to prevent the matter and antimatter from perfect cancellation – and without it we would not be here to wonder about this remarkable universe. In this way, the matter and anti-matter drained away, leaving behind a universe filled with light… except for that tiny residue. As the universe expanded and cooled, the anti-electrons started to fuse with the electrons and the antiprotons fused with the protons, converting them into particles of light. ![]() ![]() That fleeting moment saw the production of exactly equal amounts of matter and antimatter, all mixed together in a hot plasma. The vastly outnumbered matter particles appear to be a tiny residue left over after a spectacular fireworks display that occurred within the first second after the big bang. In other words, the universe is made almost entirely out of light. But the situation is a precarious one for every particle of matter in the universe, there are around a billion particles of light. It is just as well that there is some matter left behind, because by matter we mean particles such as electrons and protons, the things that build atoms, people, planets and stars. Both results touch on one of the biggest unsolved problems in fundamental physics: why is there any matter left in the universe? In China, the Daya Bay reactor, in Guangdong province, near Hong Kong, has been used to confirm that neutrinos might soon be taking centre stage in our understanding of how the universe came to be. At Cern, in Geneva, antimatter atoms have been studied for the first time by a few dozen scientists working on the Alpha experiment. Over the past two weeks, scientific results first from Cern and then from an experiment using a nuclear reactor in China have hit the headlines, at least in the world of particle physics.
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