Gravity ties our bodies to planet Earth but it does not define the limits of the soaring human mind. In November 1915 - exactly one century ago - this was proven to be true when Albert Einstein, in a series of lectures at the Prussian Academy of Sciences, presented a theory that would revolutionise how we view gravity - and physics itself. For two centuries, Newton’s remarkably simple and elegant theory of universal gravitation had seemed to explain the matter well. But, as is increasingly true for physics, simple just doesn’t cut it anymore.
Einstein’s starting point for general relativity was his theory of special relativity, published in 1905. This explained how to formulate the laws of physics in the absence of gravity. At the centre…show more content… While the laws of physics are universal, it says, different viewers will see the timing of events differently depending on how fast they are travelling. An event that would seem to take 1,000 years when viewed from Earth may seem to take just a second for someone in a spacecraft travelling at great speed.
At the centre of Einstein’s theories is the fact that the speed of light is independent of the motion of the observer who is measuring the speed. This is strange, because common sense suggests that if you sit in your car alongside a railroad track, a train passing by will seem to be moving much faster than if you followed it in the same direction.
However, if you instead sit and watch a light beam go by, it would move equally fast regardless of whether you were following it or not - a clear indication that something is wrong with common…show more content… Special relativity works only for inertial frames moving relative to one another if they are moving at constant speed - it cannot describe what happens if they are accelerating. Einstein wondered how to expand it to include such acceleration and allow for gravity, which causes acceleration and is, after all, everywhere.
He realised that the effect of gravity disappears if one doesn’t try to overcome it. He imagined people in an elevator whose cable had broken in free fall and worked out that since the objects would either float motionless or at constant speed, the people wouldn’t feel gravity. But nowadays we know this is true as we have seen it ourselves in people at the international space station. In both cases there are no forces counteracting the effect of gravity and the people experience no gravity.
Curved space-time. Mopic
Einstein also realised that the effect of gravity is the same as the effect of acceleration; driving off at high speed pushes us backward, just as if gravity were pulling us. These two clues led Einstein to general relativity. Whereas Newton had seen gravity as a force propagated between bodies, Einstein described is as pseudo force experienced because the entire interwoven fabric of space and time bends around a massive