How science actually works
Science is not a list of facts but a way of finding out. Someone suggests an explanation, then tests it with an EXPERIMENT designed so that it could prove the idea wrong. If the idea survives many tests, by many people, it becomes accepted. In everyday speech a THEORY means a guess, but in science it means the opposite: an explanation so well tested that it ties together a huge number of facts, like the theory of EVOLUTION or the atomic theory that everything is made of the ATOM.
In 1859 the French scientist Louis Pasteur settled an old argument this way. Many people believed that life could spring from nothing, since maggots and mould seemed to appear on their own. Pasteur boiled broth in flasks with long, bent, swan-like necks, which let air in but trapped the dust. The broth stayed clear for as long as the necks were intact; when he snapped a neck off, it soon went cloudy with BACTERIA. Life came from life.
Scientists who were right too early
Being right is not always enough. In 1847 a Hungarian doctor in Vienna, Ignaz Semmelweis, noticed that far more mothers died after childbirth on the ward run by doctors, who came straight from other work, than on the ward run by midwives. He made the doctors wash their hands in a chlorine solution, and deaths fell sharply. Many senior doctors refused to believe that their own hands could carry disease, and he was dismissed. He was proved right only after his death, when germs were discovered.
More recently, in 1984, an Australian doctor, Barry Marshall, was convinced that most stomach ulcers were caused by a bacterium, not by stress, but few believed him. So he drank a dish of the bacteria himself, fell ill, and cured himself with antibiotics. He and his colleague Robin Warren were awarded the Nobel Prize in 2005. Our scientists page covers more of the people who changed their subjects.
The cable that broke the speed of light
Scientists check each other's work, and that matters most when a result looks too surprising to be true. In 2011 a team in Italy announced that particles fired from Switzerland had arrived about sixty billionths of a second sooner than light could have made the journey, which would have overturned one of the firmest rules in physics. The scientists themselves asked others to find their mistake. Months later they found it: a loose fibre-optic cable had thrown off their timing. The particles had not beaten light after all, and science worked exactly as it should.
Three big branches
Science is usually split into three big branches. PHYSICS studies matter, ENERGY, forces such as GRAVITY, and the MAGNET, the ELECTRON and the rest of the universe's building blocks, all the way out to the PLANET and the GALAXY. CHEMISTRY studies what things are made of, every ELEMENT and MOLECULE, and how they change in a REACTION. BIOLOGY studies living things, from the single CELL to GENETICS and the history of life written in each FOSSIL. The MICROSCOPE and the TELESCOPE opened up the very small and the very far, and a LABORATORY, a VOLCANO and the night sky are all places where science happens. Each has its own pages in this category.