The "old" physics, the physics that Einstein could learn from Weber, was a great body of knowledge that we call Newtonian, not because Isaac Newton was responsible for all of it (he wasn't), but because his foundations were laid by Newton in the 17th century. By the late 19th century, all the disparate phenomena of the physical Universe could be explained beautifully by a handful of simple Newtonian physical laws.

But Einstein changed our way of looking at time and space. In fact Einstein argued: "There is no such thing as absolute space. There is no such thing as absolute time. Newton's foundation for all of physics was flowed. And as for the either: It does not exist." By rejecting absolute space, Einstein made absolutely meaningless the notion of "being at rest in absolute space." There is no way, he asserted, to ever measure the Earth's motion through absolute space, and that is why the Michelson - Morley experiment turned out the way it did.

One can measure the Earth's velocity only relative to other physical objects such as one can measure a train's velocity only relative to physical objects such as the ground and the air. For neither Earth or train or anything else is there any standard of absolute motion; motion is purely "relative."

By rejecting absolute space, Einstein also rejected the notion that everyone, regardless of his or her motion, must agree on the length, height, and width of some table or train or any other object. On the contrary, Einstein insisted, length, height, and width are "relative" concepts. They depend on the relative motion of the object being measured and the person doing the measuring.

By rejecting absolute time, Einstein rejected the notion that everyone, regardless of his or her motion, must experience the flow of time in the same manner. Time is relative, Einstein asserted. Each person traveling in his or her own way must experience a different time flow than others, travelling differently.