Brian Clegg

“Newton’s law of gravitation. That’s all you need (with a spot of calculus to crunch the numbers) to work out how the Earth will orbit the Sun or how an apple will fall if you let it go at a certain height. The only trouble is that Newton had no idea how this gravity thing worked. His model was simply: ‘There is an attraction between bits of stuff, and let’s not bother about why.”
― Brian Clegg, Gravitational Waves: How Einstein's spacetime ripples reveal the secrets of the universe

“Famously, Einstein said that his ‘happiest thought’ occurred here: ‘I was sitting in a chair in the Patent Office at Bern when all of a sudden a thought occurred to me. If a person falls freely he will not feel his own weight. I was startled.’ By thinking of someone falling, for example in a plummeting lift, Einstein had realised that it was impossible to distinguish acceleration and the pull of gravity. And working through the mathematical implications of this made it clear that gravity was an effect that could be produced by a distortion of space and time.”
― Brian Clegg, Gravitational Waves: How Einstein's spacetime ripples reveal the secrets of the universe