This year I decided teach something about Einstein’s theory of Relativity to my Physics class but didn’t know a thing about it. I had avoided Relativity because it sounded a bit like Relativism, the denial of absolute truth, and I wanted none of that in my science. When, however, I began to study its basic concepts, I found that Relativity fit nicely into my Christian beliefs about the limits of man’s knowledge and the importance of metaphor in epistemology.
One of the starting assumptions of Relativity is that all motion is relative. If I say a horse is moving, I probably mean that the horse is moving across the ground. If that horse were trotting on a large treadmill, he would still be moving in reference to the revolving belt, but not moving from the perspective of any observers. Motion is only meaningful if you have a frame of reference which puts the moving thing into a relationship with something else.
Press this a little further, though, and relative motion becomes a problem.
If you wanted to describe the motion of the moon, you’d say it is moving around the earth. Very good. The earth is your reference point. But the earth, too, is moving, dragging the moon with it. From the perspective of the sun, the moon is making a loopy flower-like motion, which complicates moon’s motion considerably. Which frame of reference is the real one?
It gets worse. The sun, it turns out, is moving too, and this leaves the curious mind asking where it is all really moving. What is the true backdrop against which we can measure motion and be done with it? Continue reading