Prof. Dr. Albert Einstein ( March 14, 1879 - April 18, 1955) was a famous scientist. He received the Nobel Prize in Physics in 1921.
Einstein is famous for his theories about light, matter, gravity, space, and time, which helped scientists to understand these things much better than they had before. His theories include the theory of special relativity and the theory of general relativity. His most famous equation is E = mc2.
The General Theory of Relativity was published in 1915, ten years after the Special Theory of Relativity was created. According to the General Theory of Relativity, the gravitational attraction between masses results in the masses in space and time, meaning that every object is attracted to each other, and that results in space and time.
E=mc2, also called the mass-energy equivalence, is one of the things that Einstein is most famous for. It is a famous equation in physics and math that shows what happens when mass changes to energy or energy changes to mass. The "E" in the equation stands for energy. Energy is a number which you give to objects depending on how much they can change other things.
In classical physics, momentum is explained by the equation: p = mv
where p represents momentum, m represents mass, v represents velocity speed
The energy of a photon can be computed from its frequency or wavelength. Knowing either frequency or wavelength, you can compute the photon's momentum.
In the case of motionless things with mass, since v = 0, then:
E2 = (mc2)2 + 0
which is just
E = mc2