Placeholder Image

Subtitles section Play video

  • Around nineteen-hundred, all of physics, and particularly Einstein, was in trouble: they

  • couldn't figure out how anything could moveNow before you complain that I'm exaggerating,

  • check out this cat! You can clearly see that the cat is moving away from Einstein at a

  • constant velocitybut do a little sliding switcheroo, and suddenly it looks like Einstein's

  • the one moving. This is the "old-fashioned principle of relativity," so of course it's

  • the one we teach in schoolsbut the point is that the switcheroo changes relative things,

  • like position and velocity, and not absolute ones, like the separation of Einstein from

  • his cat.

  • Now for the problem: before Einstein was even born, physicists showed that the speed of

  • light was one of those absolute things which can't be changed by a switcheroo, so any switcheroo

  • we do has to keep light moving at the same speed. But then it's obvious that we can't

  • do our sliding switcheroo at all, which means we can't explain how anything other than light

  • can move!

  • Ok, I spoke too soonthere is one solutiondo you see it? We were assuming that our

  • switcheroo had to keep every slice of time at the same, well, time. But there's no law

  • of physics that says time is an absolute thing that can't be changed by switcheroosso

  • if we just rotate the slices of time while sliding them, then we can keep the speed of

  • light the same, and explain how things can move, too.

  • Of course, Einstein didn't figure out this "special principle of relativity" in 1905

  • - it was already done by a guy named Lorentz ten years earlier. But Lorentz just thought

  • this time-rotation was a mathematical trickand it took Einstein to step in, and, you

  • guessed it, propose that "time-rotation" is real, that time really is relative, and that

  • consequently, simultaneous events relative to one observer aren't simultaneous relative

  • to another who's moving. Now that's a real switcheroo of perspective.

Around nineteen-hundred, all of physics, and particularly Einstein, was in trouble: they

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

A2 einstein relative relativity sliding absolute simultaneous

Einstein and The Special Theory of Relativity

  • 187 23
    Why Why posted on 2013/03/28
Video vocabulary