A. Michael Guillen believes that special relativity is one of the "five equations that changed the world." Professor A. P. French (MIT) also is convinced that Einstein’s scientific achievements deeply affected the intellectual development of modern physics. The special theory of relativity has unalterably changed how we perceive the world; moreover, it has ushered in an era of science called the new physics.
B. Albert Einstein postulated his theory of special relativity in 1905. It deals with bodies that move at ultra-high speeds (near the speed of light). Einstein used thought experiments (Gedanken experiments) to test his ideas. In one of his these experiments, the renowned physicist mentally explores relative simultaneity by using the example of a train and lightning striking within the view of observers on the train. According to special relativity theory, if a train is traveling West, then lightning appears to strike first in the West and subsequently in the East. On the other hand, if the train is headed East, the lightning appears to strike first in the East and then in the West for an observer riding on the train. But if the train is in a position of rest, the bolts of lightning—relative to the observers' frame of reference—strike simultaneously in the East and in the West. Einstein's theory accordingly does not abolish the notion of simultaneity altogether. It only says that a "rigid reference body" or coordinate system must be shared in order for simultaneity to obtain. The train is just such a coordinate system. Simultaneity for Einstein is thereby relative as opposed to being absolute. And the operative equation for special relativity is e = mc2.
I. Some Implications of Special Relativity for the World
A. When a person accelerates, his or her perception of time and space shrinks by a factor involving two quantities. These two quantities are v (velocity) and c (light). While acceleration makes time and space appear to shrink, it actually causes mass and energy to expand: only the perception of space and time shrinks.
B. When someone is at rest, no reductive percepts transpire. But movement that takes place near the speed of light results in percepts being significantly altered. The faster that objects move, the smaller that impressions of inches and seconds become. If one travels near the speed of light, the entire cosmos apparently shrinks ad nihilum for him or her. Reciprocally, however, a person's mass and energy seems to expand ad infinitum (since zero is the reciprocal of infinity).
C. Yet before these effects start to occur, spatial objects must be moving close to the speed of light (300,000 km/sec). Stephen Hawking points out that at 10% the rate of light-speed, an object's mass only increases .5%. At 90% light-speed, however, the same object would assume more than twice its normal mass.
II. Further Implications of Special Relativity
A. Special Relativity implies that energy and mass are two sides of the same coin. Brain Greene writes: "From e=mc², we know that mass and energy are interchangeable; like dollars and euros, they are convertible currencies (but unlike monetary currencies, they have a fixed exchange rate, given by the speed of light times itself, c²" (The Fabric of the Cosmos, page 354).
B. Mass can be converted into energy and energy can be converted into mass.
C. We now know that it's possible to split an atom and generate power from this act of fissioning. Moreover, successive fission, fusion and fission is possible. The atom bomb and the sun demonstrate how hydrogen fusion works.
French, A. P. Special Relativity. New York: Norton, 1968.
Guillen, Michael. Five Equations That Changed the World: The Power and Poetry of Mathematics. New York: MJF Books, 1995.
Hawking, S. W. A Brief History of Time. New York: Bantam Books, 2011.