Albert Einstein’s theory of relativity is actually two

separate theories: his special theory of relativity ,

postulated in the 1905 paper, The Electrodynamics

of Moving Bodies and his theory of general

relativity , an expansion of the earlier theory,

published as The Foundation of the General Theory

of Relativity in 1916. Einstein sought to explain

situations in which Newtonian physics might fail to

deal successfully with phenomena, and in so doing

proposed revolutionary changes in human concepts

of time, space, and gravity.

The special theory of relativity was based on two

main postulates: first, that the speed of light is

constant for all observers; and second, that

observers moving at constant speeds should be

subject to the same physical laws. Following this

logic, Einstein theorized that time must change

according to the speed of a moving object relative to

the frame of reference of an observer. Scientists

have tested this theory through experimentation –

proving, for example, that an atomic clock ticks

more slowly when traveling at a high speed than it

does when it is not moving. The essence of

Einstein’s paper was that both space and time are

relative (rather than absolute), which was said to

hold true in a special case, the absence of a

gravitational field. Relativity was a stunning concept

at the time; scientists all over the world debated the

veracity of Einstein’s famous equation, E=mc2,

which implied that matter and energy were

equivalent and, more specifically, that a single

particle of matter could be converted into a huge

quantity of energy. However, since the special

theory of relativity only held true in the absence of a

gravitational field, Einstein strove for 11 more years

to work gravity into his equations and discover how

relativity might work generally as well.

According to the Theory of General Relativity,

matter causes space to curve. It is posited that

gravitation is not a force, as understood by

Newtonian physics, but a curved field (an area of

space under the influence of a force) in the space-

time continuum that is actually created by the

presence of mass. According to Einstein, that theory

could be tested by measuring the deflection of

starlight traveling near the sun; he correctly

asserted that light deflection would be twice that

expected by Newton’s laws. This theory also

explained why the light from stars in a strong

gravitational field was closer to the red end of the

spectrum than those in a weaker one.

For the final thirty years of his life, Einstein

attempted to find a unified field theory , in which the

properties of all matter and energy could be

expressed in a single equation. His search was

confounded by quantum theory ‘s uncertainty

principle , which stated that the movement of a

single particle could never be accurately measured,

because speed and position could not be

simultaneously assessed with any degree of

assurance. Although he was unable to find the

comprehensive theory that he sought, Einstein’s

pioneering work has allowed countless other

scientists to carry on the quest for what some have

called “the holy grail of physicists.”

# Special Theory Of Relativity

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