How a drinking bird toy works


It’s drinking the water! this is the
greatest invention in the world you’ll make a million dollars! – A drinking bird is
some thermodynamic machine that seems to go up and down forever. In this video
you’ll see how it works I will show a speed up of a live stream that we
recently did, showing how a long time a drinking bird will run in total. How does a
drinking bird work? We have this set up a cup of water.
This glass construction with dichloromethane inside and a cylinder
tube. Notice the tube is longer in the bottom than the top. And we have
rotational axis and then we have a head. That’s a pretty drinking bird if I have
to say myself. Anyways first you need a hot environment we will represent that with red atoms. Next you need to wet the head. Okay so now the head is wet the water
will start to evaporate, going from a liquid to a gas. That will cause evaporative cooling. You know this effect after taking a shower
the water evaporates and cools off – like this cat. The cat sweat and it contains a
gigantic number of water molecules each molecule with different speeds. The
temperature is the average of all these speeds. The water molecules – the ones with
the faster speeds are the ones that escapes the surface boundary force, to
evaporate into air. The remaining water molecules has a lower average speed of
movements. And then we see a lower temperature. Also the substance
dichloromethane is actually everywhere in the form of gas the cooling causes this dichlormethane to condense. This means going from gas form to liquid form. Now look at this equation for the ideal gas. It says the pressure times the
volume should equal the amount of molecules times the gas constant times
temperature. We just conclude the temperature T is dropping as well as the
number of molecules n. Something on the other side of the equation must change
as well because this is approximative an ideal gas. We know the volume is
constant and so the pressure must drop. We have a pressure difference between
the drinking birds head and the bottom of it. This pressure difference will cause
the fluid to rise. Just like I’m showing here but this giant drinking straw and some
water the pressure difference between my mouth and the water just pushes the
water up. This will shift the center of mass and the net torque around the axis
will cause the bird to rotate. Actually just like this seesaw. The sudden change
in the mass causes it to rotate over. Now watch the bottom of the drinking bird – it’s very smart. As the bird is tipping over the surface goes under this tube,
where the dichloromethane is being sucked up in. That caused the
dichloromethane to fall back again and this shifts the balance so the bird will fall back again. I can show this effect the giant straw again if I lift up the suckd
water just above the water level everything falls down. This will cause everything to reset the
dichloromethane is falling down causing the drinking bird to stand again. Now the head is wet again and it will start the evaporative. Cooling this goes on and on
and on… But for how long? well here is the livestream showing a
total run you probably figured it will run long as the room is hot and as long
the drinking bird can reach the water in the club so yeah I just have to wait for
the water to vaporize. Tt turns out a drinking bird will run for 144 hours. Now
I have a question for you why can’t use a normal thermometer that works only by
expanding a liquid to build a drinking bird? Then it wouldn’t need a pressure
difference and therefore we didn’t need no water and it would run forever.
Why can’t do that? Comment below. I hope you enjoyed this video
next time I’ll save your life if you’re ever in a situation like this and I’ll
tell you the actual physics behind it. Consider of supporting these physics
videos by either subscribing or joining me on patreon

20 thoughts on “How a drinking bird toy works

  1. You can't really use a normal thermometer because the liquid touching the top probably wouldn't cool the "fluid ball" at the bottom which is always hanging in air.

    But you could equally well make a different version that starts with the "fluid ball" in a hot environment, and the rising of the fluid flips the thermometer lifting the container out of the hot environment.

    On a side note, I don't know if you've stumbled on it, but there's a "drinking bird of the second kind" based on osmosis.
    http://mpalffy.lci.kent.edu/papers/dbpublished.pdf

  2. Because perpetual motion is impossible

    Every motion needs an energy source. If there's nothing left, the motion will stop.

  3. Great video ! can you please tell me the answer of your question i couldn't figure it out ! also can you please give me the name of the software you used to make this animation ? thanks in advance !

  4. While watching this video, I saw one in its recommendation line up which was odd. Why is the video "Understand calculus in 10 minutes" 20 minutes long???

  5. Are you familiar with sprag or one way bearings? I would like to see some one put several of these devices on one shaft with sprags and a flywheel at the end. I think you could get continuous rotation.

  6. Lmao just saw that Simpson’s episode and thought to myself I’ve only ever seen these in cartoons I’m gonna find a video of the real thing

  7. .. What you want more thermodynamics?? well ok let's test and explain how to cool down coffee faster: https://www.youtube.com/watch?v=KOsYsrhnODs

  8. Wow, no one has ever been able to explain to me how the drinking bird works. Even after watching this video, no one has ever been able to explain to me how the drinking birds works! The search continues 🙁

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