Albert Einstein was born in Germany, in the city of Ulm. His father had a company that made electrical equipment. Albert had one sister, who was born after him. Albert grew up in Munich, a city in Germany, and he started school in Munich, and Albert took violin lessons as a boy. When Albert was four or five years old, his father showed him a compass. The compass deeply impressed Albert as a little boy, and Albert could not see what made the compass needle move. At age 16, Einstein imagined chasing after a beam of light, and this thought experiment played a role in his later work on special relativity. Einstein did very well in math and science at school. Einstein first proposed his special theory of relativity in 1905. Special relativity revealed that space and time are united in a fabric known as space-time. In 1905 he also earned his doctor's degree from the University of Zurich.
Albert Einstein was a physicist. 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. Einstein recognized that if you move away from a clock near the speed of light, the clock you see will be slow. It is impossible for any matter to travel faster than the speed of light. According to relativity, a twin who travels near the speed of light and returns would be younger than the twin who stayed on Earth. Muons made by cosmic rays reach Earth's surface because their time runs about 40 times slower than an observer on Earth experiences.
In 1905, Einstein published four groundbreaking science articles while he worked at the patent office. A fourth 1905 paper by Einstein was about the relationship between mass and energy, which had been viewed as completely separate. Einstein became famous around the world. The equation E=mc2 says that energy equals mass times the speed of light squared. In nuclear fusion, which happens inside the Sun and other stars, two nuclei merge into a heavier nucleus that has less mass than the two lighter nuclei. The leftover mass becomes energy. The mass of a helium nucleus is less than the sum of the masses of its building blocks, which E=mc2 explains as binding energy.
In 1913, Einstein urged astronomers to measure the effect of gravity on starlight, and he published his general theory of relativity in 1915. General relativity says that gravity is how mass warps space and time. In 1919, astronomers photographed stars during a total solar eclipse to test whether the Sun's gravity bends starlight. General relativity gave a more accurate prediction of planetary orbits around the Sun than Newton's theory did. Newton's equations are still used to calculate all but the most extreme motions, even though Einstein's theory superseded them. General relativity was the first major theory of gravity since Newton's, more than 250 years before. His ideas changed how scientists think about time, space and the universe.
Words to know
- fusion: nuclei merging
