Albert Einstein (1879-1955) was the most famous and influential scientist of the 20th century.
Einstein was half German and half Swiss, but when Hitler came to power in 1933, Einstein made his home in the USA.
Einstein’s fame rests on his two theories of relativity (see Relativity).
His theory of special relativity was published in 1905 while he worked in the Patent Office in Bern, Switzerland.
In 1905 Einstein also explained the photoelectric effect. From these ideas, photo cells were developed. These form the basis of TV cameras, burglar alarms and other devices.
Einstein completed his theory of general relativity in 1915 while Germany was at war.
Einstein was not satisfied with his theory of general relativity because it did not include electromagnetism. He spent the last 25 years of his life trying to develop a ‘unified field theory’ to include it.
Einstein was once reported to have said that only 12 people in the world could understand his theory. He later denied saying it.
Einstein suggested to the US government that Germany was almost certainly developing an atomic weapon as World War 2 started. The US began developing one too.
Einstein was married twice. His first wife was Mileva Maric. His second wife, Elsa, was also his first cousin.
The great scientist Albert Einstein (1879-1955) is most famous for creating the two theories of relativity.
Special relativity (1905) shows that all measurements are relative, including time and speed. Time and speed depend on where you measure them.
Light, the fastest thing in the Universe, is the same speed everywhere. It always passes at the same speed no matter where you are or how fast you are going.
Special relativity shows that as things travel faster, they seem to shrink in length and get heavier. Their time stretches too – their clocks seem to run slower.
The theory of general relativity includes the idea of special relativity, but also shows how gravity works.
General relativity shows that gravity’s pull is acceleration (speed) – gravity and acceleration are the same.
When things are falling their acceleration cancels out gravity, which is why astronauts in orbit are weightless.
If gravity and acceleration are the same, gravity must bend light rays simply by stretching space (and time).
Gravity works by bending space (and time). ‘Matter tells space how to bend; space tells matter how to move.
General relativity predicts that light rays from distant stars will be bent by the gravitational pull of stars they pass.