Relativity for dummys *simpler words in asterix*: General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field (for example when standing on the surface of the Earth) are physically identical *meaning any object in space has its own independent gravitational field*. The upshot of this is that free fall is inertial motion: an object in free fall is falling because that is how objects move when there is no force being exerted on them *gravitational fields interacting and attracting one another*, instead of this being due to the force of gravity *an object "pulling" you to its surface* as is the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects cannot accelerate with respect to each other *meaning objects in space only move when a singular force acts upon it*, but objects in free fall do so *meaning each object in free fall according to classical mechanics fall at the same rate*. To resolve this difficulty Einstein first proposed that spacetime is curved *meaning any vaccum that has any form of mass inside causes spacetime to expand and contract*. In 1915, he devised the Einstein field equations which relate the curvature of spacetime with the mass, energy, and momentum within it.
Posted on: Wed, 03 Jul 2013 07:58:29 +0000
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