Albert Einstein (1879–1955) was a German-born physicist who made some of the greatest contributions to modern science. He devised the equation E=mc², linking mass and energy. Einstein thought that the Newtonian laws of motion, first proposed by Isaac Newton in the 17th century, could no longer hold true now that the laws of electromagnetism were understood. This belief led to the development of his Special Theory of Relativity. He then realized that the principle of relativity could also be applied to understanding how gravity worked, and so he later developed the General Theory of Relativity. In 1921 Albert Einstein received the Nobel Prize in Physics.

Early life

Albert Einstein was born in Ulm in southwestern Germany on 14th March 1879. A quiet child, he barely spoke until the age of three. Unhappy with the standard of teaching at his school, he moved with his family to Italy after his father's electrical business failed.

Einstein studied at the Federal Institute of Technology in Zurich, graduating in 1900. He found it difficult to obtain a university post, eventually accepting a job at the Swiss Patent Office in Berne. This gave him time to do his own work on physics. In 1903, he married Mileva Maric, a fellow student at the Zurich Institute.

Four papers

In 1905, Einstein received his doctorate from the University of Zurich. In the same year, he wrote four scientific papers—all of which turned out to be major milestones in science. The first put forward the idea that light, which behaves as if it travels in wave form, also sometimes behaved like a stream of energetic particles, later called "quanta." The second offered a proof for the existence of molecules and atoms. The third proposed a Theory of Relativity. The fourth showed that mass and energy should be thought of as two parts of the same thing, and the relationship between them could be stated in the equation E=mc².

E=mc²

Einstein's famous equation E=mc² gives the mathematical relationship between mass and energy : energy (E) equals mass (m) times the velocity of light in a vacuum (c) squared. Because the velocity of light is extremely high—nearly 300,000 kilometres per second—a very small amount of mass represents a very large amount of energy. For example, a tiny amount of matter in the Sun (hydrogen atomic nuclei) can produce colossal amounts of energy as the the atoms fuse together.

General Theory

From 1909, Einstein took a series of university posts in Zurich and Prague. In 1914 he was appointed director of the Kaiser Wilhelm Institute for Physics in Berlin. Freed from teaching duties, he was able to concentrate on his ideas about relativity, and in 1915 completed his General Theory of Relativity.
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Einstein wanted to extend his theory of relativity to include acceleration, the gathering of speed that is due, for example, to the effect of gravity. In his General Theory, he showed that gravity, instead of being viewed as the pull exerted by another object, could be seen as the bending of space-time around that object—in the same way that a person can bend a trampoline when standing on it—causing passing bodies to fall in towards it.

By Einstein's theory, a massive object in space-time created a large “dent” in space into which light and matter would fall. The denser the object, the greater the dent. So the Sun would make only a shallow dent, whereas a black hole (the relic of a supergiant star that has exploded to become the densest object of all—unknown in Einstein's time), created a dent so deep that nothing, not even time, could escape from it.

​​​​​​​A good way to picture this event would be to imagine a star in space as ball on a rubber sheet. A massive object like a star would “bend” space and anything close to it will fall in towards it. If the ball were so heavy that the sheet stretched into a long, deep tube, the result would be a black hole.

Nobel Prize

Einstein received the 1921 Nobel Prize in Physics. During the 1920s he lectured in Europe, North and South America and Palestine, where he was involved in the establishment of the Hebrew University in Jerusalem.

As a Jew, Einstein became the focus of hostility from the Nazis in his native Germany during the 1930s, so in 1933 he emigrated to the USA. He took a position at the Institute of Advanced Study in Princeton, New Jersey.

In 1939, Einstein signed a letter warning US President Franklin D. Roosevelt of the possibility that the Germans might be building atomic weapons, and recommended that the USA launch a similar programme itself. He changed his mind after the end of World War II, and campaigned strongly to end the threat of nuclear war.

​​​​​​​Albert Einstein died in Princeton on 18th April 1955.