The Theory of Relativity

[cacian]

I am trying understand the various points/ideas of this theory and so would like some point of views on it.

Anything added or discussed is most welcome.

[Norm53]

There are two theories: Special and General. Special assumes the absence of gravity; General assumes gravity.

Special has two postulates, both confirmed by experiments:
The laws of physics are the same in any inertial frame of reference; i.e., no acceleration.
The speed of light in a vacuum is the same for all observers, irrespective of their motion or of the motion of the light source.

Some consequences:
Time dilation: Moving clocks tick more slowly than an observer's stationary clock.
Length contraction: Objects are shortened in the direction that they are moving with respect to the observer.

General Relativity: An object's gravity affects the space and time around it.

Some consequences:
Light bends in a gravitational field.
Clocks farther away from the source of gravity run faster.

These theories (actually, facts) became practical with the invention of satellites. Their clocks need correction for both relativities since they affect time in opposite directions by unequal amounts.