Special relativity is the
physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein in the paper
"On the Electrodynamics of Moving Bodies". It generalizes Galileo's principle of relativity–that all uniform
motion is relative, and that there is no absolute and well-defined state of rest (no privileged reference
frames)–from mechanics to all the laws of physics, including both the laws of mechanics and of electrodynamics,
whatever they may be. Special relativity incorporates the principle that the speed of light is the same for all
inertial observers regardless of the state of motion of the source.
This theory has a wide range of
consequences which have been experimentally verified, including counter-intuitive ones such as length contraction,
time dilation and relativity of simultaneity, contradicting the classical notion that the duration of the time
interval between two events is equal for all observers. (On the other hand, it introduces the space-time interval,
which is invariant.) Combined with other laws of physics, the two postulates of special relativity predict the
equivalence of matter and energy, as expressed in the mass-energy equivalence formula E = mc2, where c is the
speed of light in a vacuum. The predictions of special relativity agree well with Newtonian mechanics in their
common realm of applicability, specifically in experiments in which all velocities are small compared to the speed
Special relativity reveals that c is not just the velocity of a certain phenomenon, namely the
propagation of electromagnetic radiation (light)—but rather a fundamental feature of the way space and time are
unified as spacetime. A consequence of this is that it is impossible for any particle that has mass to be
accelerated to the speed of light.
The basic translational equations of Albert Einstein's Special Theory of Relativity are
Einsteinian Commandment: "Thou shalt not add thine own speed directly to the speed of
thine fellow traveler."
c = speed of light. Primed
quantities are moving at speed "v"
Moving clocks run slow
Moving rods appear shorter
Moving mass increases
, relating frames S and S",
"correction factor" for high relative velocities compared to c.
Thanks to Dr. DonZi for this equation