Related Forms:A Closer Look Albert Einstein's two theories of
relativity were the first successful revisions of Newtonian
mechanics—a mechanics so simple and intuitive that it was held
to be a permanent fixture of physics. Uniting the theories is
the idea that two observers traveling relative to each other may
have different perceptions of time and space, yet the laws of
nature are still uniform, and certain properties always remain
invariant. Einstein developed the first theory, the theory of
Special Relativity (1905), to explain and extend certain
consequences of Maxwell's equations describing electromagnetism,
in particular, addressing a puzzle surrounding the speed of
light in a vacuum, which was predicted always to be the same,
whether the light source is stationary or moving. Special
Relativity considers the laws of nature from the point of view
of frames of reference upon which no forces are acting, and
describes the way time, distance, mass, and energy must be
perceived by observers who are in uniform