[MUSIC PLAYING] What if I told you I built a
machine that creates energy? My ingenious design
works like this. As the wheel turns, the
coins fall in the slots so that one side of
the wheel is always heavier than the
other, which would keep pulling that side
down, and the wheel would never stop turning. Without so much as a push,
this wheel would spin forever. Think about the possibilities. I could build a giant
fleet of wind turbines that turn without wind to
power the entire Earth. We wouldn't have to burn
fossil fuels anymore. This could solve climate change. So let's see it
in action, or not, because it doesn't
actually work. You may have seen
this wheel before, and there is a reason
it doesn't work-- well, physics, but also
friction here on the axle, which will eventually stop any
wheel from continuing to spin. But then there's
also gravity, so what I said earlier about
one side of the wheel being heavier than the other was
misleading because of the way gravity works on wheels. Imagine a regular wheel. Its center of mass is at
the center of the wheel. Now, imagine a wheel
with a single coin in it. It might swing back and
forth a couple times, but it won't rotate. Add a second coin. Add a third coin. The wheel swings back
and forth, slowing down until it stops where
the center of gravity is at its lowest
position, always, so the unbalanced
wheel will swing back and forth like a sad
pendulum until friction wins. This wheel is a
perpetual motion machine, a device that is supposed
to move without any energy. NARRATOR: But by far the most
persistent dream of inventors has been to get
something for nothing. That is to create a machine
that will start itself, overcome all friction, and
still have enough power left to do useful work--
in short, perpetual motion machines. In countless
instances in history, people have claimed that
they've made a perpetual motion machine-- Bhaskara's
unbalanced mercury wheel in the 1100s, Zimara's
self-blowing windmill in the 1500s, the capillary bowl
where capillary action forces the water upwards, the
Oxford electric bell, which takes back and forth due to
charge repulsion, and so on. In fact, the US
Patent Office stopped granting patents for
perpetual motion machines without a working prototype. The reason you've never
heard of Cox's timepiece and you don't power your
smartphone with a capillary bowl is that perpetual
motion machines are the snake oil of physics. They are impossible. This is the classic
drinking bird toy. It tips itself into a glass of
water and then rights itself and then tips again, over and
over, looking forever thirsty. Where's the source of energy? At room temperature,
inside the bird is part liquid and part vapor. The bird contains a substance
called dichloromethane, the same stuff in
this little toy, which boils at a much lower
temperature than water. When the bird dips its
beak into the water, the bird's top cools down. Because of the ideal
gas law, PV equals nkT, the pressure in the tube
at the top of the bird is lower than the pressure
in the bottom of the bird. This pressure difference
pushes the liquid into the top of the head. The toy gets top
heavy and tips over. When the bird tips over,
the bottom of the tube is exposed to the vapor, which
rises up and pushes the liquid back into the bottom. The bird stands up, and
the cycle continues. But it's not perpetual motion. There is an energy source making
this bird drink over and over, but it's hard to spot. The energy source for the
bird is the ambient heat in the room. Bear with me. The water cooled
the bird's beak, creating a temperature
difference between the top and bottom, and that caused
the pressure difference that made the liquid flow to the
top and tipped the bird over. When the pressure equalized,
the top and bottom of the bird became the same temperature,
but slightly cooler than it started out. Then the room warms
the bird up again, and that's where we
see our energy source. This back and forth between
pressure and temperature is what causes Earth's
weather, and though it seems like weather and
wind and storms never stop, they're powered
by the sun's heat. So even Earth's weather isn't
a perpetual motion machine. Now, there is a more fundamental
reason why these machines are impossible, and it's called
the law of conservation of energy, which states that
energy can neither be created nor destroyed. Energy never comes for free. If you see a machine
producing motion, heat, light, or another form of energy, keep
looking for the energy source. I repeat, keep looking
for the energy source. So now you know. If anyone tells you they've
built a perpetual motion machine, tell them to peddle
their wares elsewhere. Thank you so much for watching. It's all very, and so are
you if you think it'll work. NARRATOR: You can't get
something for nothing. [MUSIC PLAYING]
No. No they are not.
This woman has a band camp kind of feel.
Yeah but there is no reason to not pursue them. It is possible to make something 99.99 efficient. But the fucking argument well perpetual motion is impossible, yeah no shit fucklord everything knows that. It's doesn't mean we shouldn't strive for the greatest efficiency possible.