## Life of Albert Einstein

Einstein, in his studies, concluded that there was no distinction between matter and energy, which had equivalent masses. The equation E = mc² is considered as the landmark of the evolution of atomic energy and one of the most famous equations in the world.

In physics, **mass-energy equivalence** is the principle that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein's famous formula:

This formula states that the equivalent energy (*E*) can be calculated as the mass (*m*) multiplied by the speed of light (*c* = ~3×10^{8} m/s) squared. Similarly, anything having energy exhibits a corresponding mass *m* given by its energy *E* divided by the speed of light squared *c*^{2}. Because the speed of light is a large number in everyday units, the formula implies that even an everyday object at rest with a modest amount of mass has a very large amount of energy intrinsically. Chemical reactions, nuclear reactions, and other energy transformations may cause a system to lose some of its energy content to the environment (and thus some corresponding mass), releasing it as the radiant energy of light or as thermal energy for example.

Mass–energy equivalence arose originally from special relativity as a paradox described by Henri Poincaré. Einstein proposed it on 21 November 1905, in the paper *Does the inertia of a body depend upon its energy-content?*, one of his *Annus Mirabilis* (Miraculous Year) papers. Einstein was the first to propose that the equivalence of mass and energy is a general principle and a consequence of the symmetries of space and time.

A consequence of the mass-energy equivalence is that if a body is stationary, it still has some internal or intrinsic energy, called its rest energy, corresponding to its rest mass. When the body is in motion, its total energy is greater than its rest energy, and equivalently its *total mass* (also called relativistic mass in this context) is greater than its rest mass. This rest mass is also called the intrinsic or invariant mass because it remains the same regardless of this motion, even for the extreme speeds or gravity considered in special and general relativity.

The mass-energy formula also serves to convert units of mass to units of energy (and vice versa), no matter what system of measurement units is used.

The scientist presented the Theory of Relativity in 1915. The “General Foundation of the Theory of Relativity” was published in 1916.

Three years later, already separated from Mileva, he married Elsa, his cousin. This year, with the proving of the theory of relativity, through experiments done, during the solar eclipse, Einstein gained prominence worldwide.

The Nobel Prize in Physics came in 1921 That year, the scientist joined the ranks of the League of Nations Intellectual Cooperation Organization. However the Nobel Prize in Physics 1921 was awarded to Albert Einstein for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect that was instrumental in establishing quantum theory.

During the selection process in 1921, the Nobel Committee for Physics decided that none of the year's nominations met the criteria as outlined in the will of Alfred Nobel. According to the Nobel Foundation statutes, the Nobel Prize can in such a case be reserved until the following year, and this statute was then applied. Albert Einstein, therefore, received his Nobel prize for 1921 one year later, in 1922.

He presided over the Hebrew University of Jerusalem, from 1925 to 1928. With the rise of Adolf Hitler, Einstein again renounced German citizenship and left the country in 1933. He moved to the United States, where he was part of the Institute of Advanced Studies at Princeton University. He became an American citizen in 1940 but did not give up Swiss citizenship.

Einstein resigned as director in 1945, without leaving his job at Princeton University. That institution started, in 1941, the Manhattan Project, to create the atomic bomb, but Einstein did not participate in that project.

He spent 25 years of his life trying to conclude the Unitary Theory of the Field, in which he intended to cover gravitational and magnetic phenomena. He was unable to develop such a theory or prove its non-existence.

Albert Einstein had a very productive intellectual life. Together with Sigmund Freud, he wrote, in 1933, the work “Why War?”. A few years later, two other works were published: “The World as I See It” and “My Last Years”, in which he presents his knowledge of the universe.

Einstein was even invited to assume the presidency of The state of Israel, in 1952, by the then Prime Minister Ben-Gurion. The scientist declined the invitation due to health problems.

Before he died, Einstein wrote a letter to Bertrand Russell, one of the greatest mathematicians in the world, confirming the decision to include his name in all manifestos against nuclear weapons. At the age of 76 years old, Einstein died in New Jersey on April 18, 1955. The body was cremated and his legacy eternalized as one of the greatest physicists in the world.