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Perpetual motion machines are badly named.

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

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

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

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

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

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it would give out more energy than is put
in:

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enough to overcome friction, enough to overcome
air resistance,

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enough to keep going until mechanical failure.

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And like a wind turbine,

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

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There are, obviously, some physics objections
to this.

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The laws of thermodynamics always hold true.

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

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It is the original, two centuries old

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from the archives of the Royal Institution
in London,

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

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It’s an unbalanced wheel,

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and there have been many perpetual motion
machines like it.

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

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advertising a café: and according to Popular
Mechanics,

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

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And there was an inventor in 1829 who was
sure

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that a carriage with conical wheels

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

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They all work on the same principle:

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

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constantly unbalanced in the same direction.

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

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there are more ball bearings on one side,

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so that side should be heavier,

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and when one gets near the top...

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

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This doesn’t work, obviously.

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And that’s why Thomas Young built this machine:

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to demonstrate that it’s impossible.

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There may be more ball bearings on that side,

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

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No matter how much you complicate it,

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this wheel will just rock back and forth

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and eventually settle where the centre of
gravity is lowest,

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or where friction stops it.

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But imagine if perpetual motion machines did
work.

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Which isn’t difficult to imagine, apparently:

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there are all sorts of snake-oil companies

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

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

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

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refuse to even entertain the idea of perpetual
motion machines.

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

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

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against the idea of free energy.

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Because regardless of how it’s powered,

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whether it’s an unbalanced wheel or something
else,

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

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

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and so on, and so on, and so on?

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

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and rotate the Earth with it.

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Or what happens if you plug it into itself?

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

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then after a few seconds, you’ve got a bomb.

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Thank you very much to the Royal Institution!

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

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along with someone from their team.

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Go check it out!