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  • Perpetual motion machines are badly named.

  • A true perpetual motion machine doesn't just keep spinning forever:

  • if you were to set an object spinning out in intergalactic space,

  • in some ideal true vacuum, it would keep spinning forever.

  • You just wouldn't be able to get any useful work out of it.

  • If someone actually built a perpetual motion machine, a true one,

  • it would give out more energy than is put in:

  • enough to overcome friction, enough to overcome air resistance,

  • enough to keep going until mechanical failure.

  • And like a wind turbine,

  • it'd let you take some of that extra energy for your own use.

  • There are, obviously, some physics objections to this.

  • The laws of thermodynamics always hold true.

  • This here is a device made by Thomas Young in 1807.

  • It is the original, two centuries old

  • from the archives of the Royal Institution in London,

  • which is why I have to wear gloves to touch it.

  • It's an unbalanced wheel,

  • and there have been many perpetual motion machines like it.

  • There was a giant one in Los Angeles in the early 20th century,

  • advertising a café: and according to Popular Mechanics,

  • it kept going until there was a city-wide power cut.

  • And there was an inventor in 1829 who was sure

  • that a carriage with conical wheels

  • would roll around the world “'till time shall be no more”.

  • They all work on the same principle:

  • cheat the centre of gravity so it's always on one side,

  • constantly unbalanced in the same direction.

  • In this case, if you draw a line down the middle,

  • there are more ball bearings on one side,

  • so that side should be heavier,

  • and when one gets near the top...

  • rolls over, so that side over there is constantly being pushed down.

  • This doesn't work, obviously.

  • And that's why Thomas Young built this machine:

  • to demonstrate that it's impossible.

  • There may be more ball bearings on that side,

  • but the ones on this side are further away from the centre.

  • No matter how much you complicate it,

  • this wheel will just rock back and forth

  • and eventually settle where the centre of gravity is lowest,

  • or where friction stops it.

  • But imagine if perpetual motion machines did work.

  • Which isn't difficult to imagine, apparently:

  • there are all sorts of snake-oil companies

  • who successfully sucker investors into giving up surprising amounts of money,

  • and then never produce any actual proof of a working prototype.

  • There have been so many attempts that both the US patent office and the UK "pay-tent" office

  • refuse to even entertain the idea of perpetual motion machines.

  • Now, you can argue physics and thermodynamics all you want,

  • but there's a more common-sense argument against perpetual motion machines,

  • against the idea of free energy.

  • Because regardless of how it's powered,

  • whether it's an unbalanced wheel or something else,

  • if you have a magic box that can give out more energy than it takes in:

  • what happens if you use a small one to power a bigger one,

  • and so on, and so on, and so on?

  • You could start with something the size of a grain of sand,

  • and rotate the Earth with it.

  • Or what happens if you plug it into itself?

  • If you have something that multiplies the energy you put in...

  • then after a few seconds, you've got a bomb.

  • Thank you very much to the Royal Institution!

  • Over on their channel I'm debunking three other types of perpetual motion machines

  • along with someone from their team.

  • Go check it out!

Perpetual motion machines are badly named.


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B1 中級

車輪、爆弾、永久運動マシン (Wheels, Bombs, and Perpetual Motion Machines)

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    林宜悉 に公開 2021 年 01 月 14 日