Albert Einstein : The Man who shaped Cosmology

Einstein was told two things when he mentioned wanting to solve the problem of gravity: one was that it simply couldn’t be done, the other was that no one would believe him even if he did. In response he created his greatest achievement, the theory of general relativity. General relativity did for gravity what even Newton couldn’t do for it gave it an explanation, a mechanism by which things fall and orbit and distort time. In fact, creating general relativity involved confronting Newton and his ideas of gravity, the latter which described it as a mysterious force that pulled objects together. Though in truth, even Newton himself didn’t understand how this would work (it involved having the force act through empty space) and bitterly criticized his own theory of gravity. Yet despite the questions it left unanswered, Newton’s formulas for gravity were still used for decades to accurately predict the motions of planets, as a foundation for the universal laws of physics, and to send men to the moon. Einstein had brought together space and time into what was aptly called spacetime. While the natural motion of things is to follow the simplest path through spacetime, mass curves this fabric so that we move towards centers of more mass. This is the force we call gravity.

How does this describe the orbits of planets and moons? Newtonian gravity says the sun is pulling us inward but we don’t fall into it because the Earth is also moving sideways at the same time as it’s being pulled towards the sun, giving us the elliptical orbit we take around it. But according to general relativity, the enormous mass of the sun warps the space around Earth and this space is what’s pushing the Earth towards the sun…