Albert Einstein of course gave us a theory of gravity which gave deeper insights into gravity.  We’ve had, ever since Sir Isaac Newton, a theory of gravity which works pretty well, and is sufficient to understand the orbit of planets and to guide space probes to the planets, et cetera.  But it breaks down if the speeds get very high or if gravity there is strong.  And there are places in the cosmos where gravity is strong.

Einstein’s theory not only has broader applicability, but it gives a deeper insight into why gravity behaves the way it does.  He had a new way of looking at gravity and space and time.  And the most extreme manifestations of Einstein’s theory are black holes, where an object has contracted, got so small that not even light can escape it’s gravitational field.  And it leaves a sort of gravitational imprint frozen in the space that’s left.  Black holes were probably the most remarkable conjecture from Einstein’s theory, but the evidence for them didn’t come really until the quasars in the late 1960’s, which were the first indirect evidence.  But since that time it’s been possible to understand how gas flows near a black hole, and much more recently to study what happens when black holes crash together and produce gravitational waves, which is a little ripple in space itself.

So I would say that over the last 50 years, Einstein’s theory has been vindicated.  Fifty years ago, there were only a few tests of it, which weren’t very precise and only applied when it was weak.  But now I think we’ve got very strong reasons for believing that it is the right insight into space and time, and black holes are governed by the equations of Einstein.  Also that the early big bang, which set our universe expanding, was governed by those same equations.  So we do have a very good theory which explains gravity and the large scale structure of the universe.