Throughout the history of relativity, starting with Albert Einstein, it has been an unknown terrain, filled with unknown variables and constants. Steven Hawking travels through this history discussing the full scope of theories, similarities, contrasts, and new discoveries in this field. This grasps from, why the planets and light act the way they do, all the way to theoretical time travel without surpassing the speed of light.
"This might suggest that if one wanted to live longer, one should keep flying to the east so that the plane's speed is added to the earth's rotation"(Hawking 9).
"Here was direct evidence that space and time are warped and it spurred the greatest change in our perception of the universe in which we live since Euclid wrote his Elements of Geometry around 300 B.C"(Hawking 21).
"Einstein's theory of relativity, which agrees with a large number of experiments, shows that time and space are inextricably interconnected"(Hawking 33).
"The ball bearings rolling on the sheet are deflected by this curvature and go around the large ball, in the same way the planets in the gravitational field of a star can orbit it"(Hawking 34).
"As one goes back in time, the cross sections of our past light cone reach a maximum size and begin to get smaller again. Our past is pear-shaped"(Hawking 41).
The fact that the forces of the universe affects not only space, but light bends with gravity. It means that the way you view stars from far away they could end up not being there. Another thing I found very significant is that if the universe lasted forever every day and night the sky would be filled with light from every star in the universe shinning it's light on me.