Albert Einstein 1879 - 1955
Einstein's theories of special and general relativity drastically altered man's view of the universe, and his work in particle and energy theory helped make possible quantum mechanics and ultimately, the atomic bomb.
In "On a Heuristic Viewpoint Concerning the Production and Transformation of Light," which earned him the 1921 Nobel Prize in Physics, Einstein theorized that light is made up of individual quanta (photons) that demonstrate particle-like properties while collectively behaving like a wave. The hypothesis was arrived at through Einstein's examination of the photoelectric effect, a phenomenon in which some solids emit electrically charged particles when struck by light.
In a second paper, he devised a new method of counting and determining the size of the atoms and molecules in a given space, and in the third he offered a mathematical explanation for the constant erratic movement of particles suspended in a fluid, known as Brownian motion. These two papers provided indisputable evidence of the existence of atoms.
Einstein's fourth scientific work in 1905 addressed what he termed his special theory of relativity. In special relativity, time and space are not absolute, but relative to the motion of the observer. Thus, two observers traveling at great speeds in regard to each other would not necessarily observe simultaneous events in time at the same moment, nor necessarily agree in their measurements of space. In Einstein's theory, the speed of light, which is the limiting speed of any body having mass, is constant in all frames of reference.
In the fifth paper that year, an exploration of the mathematics of special relativity, Einstein announced that mass and energy were equivalent and could be calculated with an equation, E=mc2.
In 1916, he published "The Foundation of the General Theory of Relativity," which proposed that gravity, as well as motion, can affect the intervals of time and of space. According to Einstein, gravitation is not a force, as Isaac Newton had argued, but a curved field in the space-time continuum, created by the presence of mass. An object of very large gravitational mass, such as the sun, would therefore appear to warp space and time around it, which could be demonstrated by observing starlight as it skirted the sun on its way to earth. In 1919, astronomers studying a solar eclipse verified Einstein's predictions in the general theory of relativity, and he became an overnight celebrity. Later, other predictions, such as a shift in the orbit of the planet Mercury and the probable existence of black holes, were confirmed by scientists.
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