Albert Einstein's theory of relativity is of two separate theories- Special Theory of Relativity in 1905, it says that the speed of light in vacuum was independent to the motion of all observers and his General Theory of Relativity in 1915 He says that massive objects cause a distortion in space-time,which is felt as gravity
The gravity
Force of attraction between two object is known as
gravity Even as the center of the Earth
is pulling you toward it mass and weight are different concepts mass it is the
amount of matter contained in a
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 10 more years to work gravity into his
equations and discover how relativity might work generally as well.
In his theory of special relativity, determined that the speed
of light within a vacuum is the same no matter the speed at which an
observer travels. As a result, he found that space and time were interwoven
into a single continuum known as space-time. Events that occur at the same time
for one observer could occur at different times for another.
As he worked out the equations for his general
theory of relativity, Einstein realized that massive objects caused a
distortion in space-time. Imagine setting a large body in the center of a
trampoline. The body would press down into the fabric, causing it to dimple. A
marble rolled around the edge would spiral inward toward the body, pulled in
much the same way that the gravity of a planet pulls at rocks in space.
Experiment
Although instruments can neither see nor measure
space-time, several of the phenomena predicted by its warping have been
confirmed.Gravitational lensing: Light around a massive object, such as a black
hole, is bent, causing it to act as a lens for the things that
lay behind it. Astronomers routinely use this method to study stars and
galaxies behind massive objects.
Einstein's
Cross, a quasar in the Pegasus constellation, is an excellent
example of gravitational lensing. The quasar is about 8 billion light-years
from Earth, and sits behind a galaxy that is 400 million light-years away. Four
images of the quasar appear around the galaxy because the intense gravity of
the galaxy bends the light coming from the quasar.
Changes in the orbit of Mercury: The orbit of Mercury is shifting very gradually
over time, due to the curvature of space-time around the massive sun. In a few
billion years, it could even collide with the Earth.
Frame-dragging of space-time around rotating bodies: The spin of a heavy object, such as Earth, should
twist and distort the space-time around it. In 2004, NASA launched the Gravity
Probe B. The precisely calibrated satellite caused the axes of gyroscopes
inside to drift very slightly over time, a result that coincided with Einstein's
theory.
Gravitational redshift: The electromagnetic radiation of an object is
stretched out slightly inside a gravitational field. Think of the sound waves
that emanate from a siren on an emergency vehicle; as the vehicle moves toward
an observer, sound waves are compressed, but as it moves away, they are
stretched out, or redshifted. Known as the Doppler Effect, the same phenomena
occurs with waves of light at all frequencies. In 1959, two physicists, Robert
Pound and Glen Rebka, shot gamma rays of radioactive iron up the side of a
tower at Harvard University and found them to be minutely less than their
natural frequency due to distortions caused by gravity.
Gravitational waves: Violent
events, such as the collision of two black holes, are thought to be able to
create ripples in space-time known as gravitational waves. The
Laser Interferometer Gravitational Wave Observatory is presently searching for
the first signs of these tell-tale indicators.
The electromagnetic field can have waves in it that carry energy and that we call light. Likewise, the
gravitational field can have waves that carry energy and are called gravitational
waves. These may be thought of as ripples in
the curvature of spacetime that travel at the speed of light.
Just as accelerating
charges can emit electromagnetic waves, accelerating masses can emit
gravitational waves. However gravitational waves are difficult to detect
because they are very weak and no conclusive evidence has yet been reported for
their direct observation. They have been observed indirectly in
the binary pulsar. Because the arrival time of pulses from the pulsar can be measured very precisely, it can be determined that the
period of the binary systems gradually decreasing. It is found that the rate of
period change (about
75 millionths of a second each year) is what would
be expected for energy being lost to gravitational radiation, as predicted by
the Theory of General Relativity.
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. An USSR stamp dedicated to albert Einstein for his theory of
relativity
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