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## What's So Special About Relativity?

Einstein's first theory of relativity, which he published in 1905, broke
away from the Newtonian reliance on space and time as immutable frames
of reference. This theory was immediately recognized by the scientific
community as having profound implications for physics and cosmology.

Einstein's main goal was to address the apparent inconsistencies in
Maxwell's electromagnetic theory. No wonder Einstein named his paper
**The Electrodynamics of Moving Bodies**.

**Einstein's 1905 paper**

on Special Relativity

Later to become known as the **Special Theory of Relativity**, its first
postulate was that the speed of light is the same for all observers,
regardless of their motion relative to the source of the light.
The second postulate was that all observers
moving at constant speed should observe the same physical laws. Putting
these two ideas together, Einstein showed that the only way this can
happen is if time intervals and/or lengths change according to the
speed of the system relative to the observer's frame of reference.
This flies against our everyday experience but has since been demonstrated to hold in a number of very solid experiments. For example,
scientists have shown that an atomic clock travelling at high speed in a jet plane ticks more slowly than its stationary counterpart.

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Einstein's discovery of the **relativity** of space and time led to an equally revolutionary insight. Matter and energy are interrelated, even equivalent. The equivalence of matter and energy is
summed up in the famous equation:

Where m = mass and c = the speed of light.

Einstein's 1905 theory is referred to as the "special" theory because
it is limited to bodies moving in the absence of a gravitational
field. It took Einstein eleven more years to formulate a set of
general laws that took account of gravity. The result: Einstein's second
landmark paper on **General Relativity**.

Forward to General Relativity

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#### Copyright © 1995, The Board of Trustees of the University of
Illinois

*NCSA. Last modified 8/28/95.*