Sean Carroll: evaluation

Transcript context

…There’s really no difference? There is almost no difference. There’s one difference that is important, which is the following; If you have a curve in space, I’m going to draw it horizontally, because that’s usually what we do in spacetime diagrams, if you have a curve in space, you’ve heard the motto before that the shortest distance between two points is a straight line. If you have a curve in time, which is by the way, literally all of our lives, we all evolve in time. You can start with one event in spacetime, and another event in spacetime. What Minkowski points out is that the time you measure along your trajectory in the universe is precisely analogous to the distance you travel on a curve through space. By precisely, I mean it is also true that the actual distance you travel through depends on your path. You can go a straight line, shortest distance and curvy line would be longer. The time you measure in spacetime, the literal time that takes off on your clock also depends on your path, but it depends on it the other way. That the longest time between two points is a straight line. If you zig back and forth in spacetime, you take less and less time to go from point A to point B. How do we make sense of that, the difference between the observed reality and the objective reality are underneath it, or is objective reality a silly notion given general relativity?…

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