Transcription
Einstein famously said, "The past, present, and future are, you know, persistently annoying illusions." Again, do we know this to be true?
At the moment, we don't have any better physics, and I doubt the physics will get any less weird than that. But yeah, I mean I mean that's sort of the way modern physics thinks the universe may be is is a big whole thing that started from beginning to end and is all now-ish.
But if that's the case, so subjectively we can measure things. We can measure time. But but what are we measuring? If it's I mean are we making artificial time constraints? Are we are we doing it ourselves? When we when we create a clock, we create a watch, and the watch is, you know, 24 hours a day, it's running. What is it What is it measuring?
Yeah.
[laughter]
Right? That is exactly the question Albert Einstein asked. That that that is that is a deep, excellent question. And and so that was the problem. I mean in a famous thought experiment, Einstein made a clock by setting up two mirrors and having light bounce between the two mirrors, and that was the tick of the clock. Tick tick tick tick.
But but but here's the deal. So, the the clock in Einstein's experiment So, the the the the clock has, you know, two mirrors, and there's light bouncing between it, and then and that's the distance that it travels in one tick.
Right.
But now you put this mirror you put that clock on a spaceship, and the spaceship's going really fast, and as it goes by, you see that that that clock as as it streams by you really fast, you see the light make this motion. And and this line is actually longer than that line. This this line, if you measure it, that's actually a longer line that I drew than the the original one between just the two mirrors, cuz now it's at an angle. And this is what made Einstein say, "Time has to change. If anything moves, the tick of a clock change. So, whatever you measure time, whatever time is, whether you measure it with a bouncing clock or whether you measure it with a vibrating atom like we do in the Bureau of Standards, or whether you measure it with a spring that's slowly unwinding in a wristwatch, anything you can do to measure one moment to the next changes when motion is involved. There's no way to get around it. It's not just the measurement. It's time itself is changing. Any way we have to measure this thing we call time,