In 1905 Einstein suggested that the new source of energy was none other than matter itself. The route by which he reached this conclusion deserves to be traced. Early in 1905 Einstein published his great paper “On the Electrodynamics of Moving Bodies’” which laid the a foundations of what came to be called the special theory of relativity.
The cardinal notion of the special theory is that light always travels at the same speed regardless of the speed of its source. If you toss a pebble forward from a moving automobile, then the speed or the pebble equals the speed of the automobile plus the speed with which the pebble was thrown. But with light situation is different. If you turn on the headlights of a speeding car, the velocity of the light from the headlights relative to the ground does not consist of the speed of the light plus the speed of the car. According to the special theory of relativity, the speed of the light from the moving headlight is exactly the same as it would have been if the car had not been moving at all. This simple idea that the speed of light is constant relative to very (un-accelerated) frame of reference changed physics and changed the world.
In late 1905 Einstein published three page meditation on the relationship between the mass of an object and energy contained in it. He reasoned that if the expenditure of energy needed to accelerate an object resulted in an increase in the mass of an object, then a decrease in velocity must produce a decrease in the mass of an object. The exact mathematical relationship between the mass of an object and the energy it contained flowed directly from the equations of the special theory, and was expressed in the famous formula: E=mc2
that is, that the energy of a body is proportional to the mass of the body multiplied by the square of the speed of light. In 1908 physics and chemistry joined hands when Max Planck took note of Einstein’s equation and suggested that the phenomenon of radioactivity could be explained as the direct transformation of matter into energy.In the years immediately following Einstein’s proposal, physicist and journalist amused themselves with calculations that a teaspoon of matter contained enough energy to power an ocean liner around the world. But even in the relatively pacific years before World War 1 the military implications of radioactivity and atomic energy did not go unnoticed.
Einstein Theory of Relativity
