Albert Einstein was a physicist. He was born in Germany, in the city of Ulm. His father had a company that made electrical equipment. When Albert was four or five years old, his father showed him a compass. The compass deeply impressed Albert as a little boy. Albert could not see what made the compass needle move. Einstein later wrote that seeing the compass as a boy made a deep and lasting impression on him. The sense of wonder that the compass gave Albert lasted his whole life. Albert Einstein also played the violin.

Einstein did very well in math and science at school. Albert finished his school studies at the Cantonal School in Aarau, Switzerland. Einstein studied at the Swiss Federal Polytechnic School in Zurich, Switzerland. He trained to be a teacher of physics and mathematics. After university, Einstein could not find a teaching job. He took a job at the patent office. At the patent office in Bern, Einstein examined inventions to decide whether they could be patented. He wrote to a friend that the patent office was where he concocted his finest ideas. In 1905, Einstein published four groundbreaking science articles while he worked there.

At age 16, Einstein imagined chasing after a beam of light. This thought experiment played a role in his later work on special relativity. His 1905 paper "On the Electrodynamics of Moving Bodies" proposed his special theory of relativity. Special relativity says the speed of light in a vacuum is the same for any observer. According to special relativity, the faster you move, the slower time passes for you. A fourth 1905 paper was about the relationship between mass and energy, which had been viewed as completely separate. Einstein is famous for the equation E=mc2. It says that energy equals mass times the speed of light squared.

Einstein won the Nobel Prize in Physics. He won the 1921 prize for his discovery of the law of the photoelectric effect, and he received it one year later, in 1922. In the photoelectric effect, light that shines on a material makes the material give off tiny charged particles. Einstein explained it by proposing that light comes in small packets of energy called quanta. He won it at a time when his ideas on relativity were still considered questionable. Einstein became famous around the world.

In 1933, Einstein left Germany for America. He never returned to Germany. That year he began work at the Institute for Advanced Study in Princeton, New Jersey. He lived and worked in Princeton in his later years. His house there was an old house with a garden at 112 Mercer Street. He spent his later years looking for a unified field theory, one set of ideas to join the laws of physics. He became a United States citizen in 1940. Einstein is quoted as saying: "The important thing is not to stop questioning."

Words to know

• quanta: energy packets