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• 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

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Einstein and The Special Theory of Relativity

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Why Why posted on 2013/03/28
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