The Assassin's Teapot Is Weird

[Music] this is an assassin's teapot it can be used to pour yourself a drink and to pour a drink for your enemy you can then down your drink to prove that the drink isn't poisoned there's no poison in there don't worry about the poison there is no poison but then when your enemy takes a drink they find out that it is poisoned and by the way this doesn't require you to spend the last few years building up an immunity to iocan powder it works straight off the bat no preparation required that's bec

ause the assassin's teapot can be used to pour three different drinks which i've shown here using three different colored liquids and by the way if you plan to poison your enemy i recommend using liquids of the same color do i need to tell the viewers that they shouldn't be trying to poison people like legally just that it would break the flow of the video film myself having a fake phone call with a lawyer in which i explain the problem and so long as i say out loud don't try to poison people th

en that should have me covered okay click the way you choose the drink is by sneakily covering up one of these holes if you cover this hole you get a blue drink if you cover this hole you get a yellow drink if you cover no holes you get a green drink so three drinks in total though actually no four drinks if you cover both holes you get the null drink but how does it work well you know me if i want to describe how a hydrodynamic mechanism works i like to make a transparent 2d version of it i'll

put a playlist of those videos in the card in the description first i needed to figure out what was going on inside the teapot and a bit like with the gloggle jug the only really sensible way to do that was to hit it with a hammer so you can see there are two chambers here side by side and they both lead up to the spout additionally one chamber leads up to this hole the other chamber leads to this hole for the 2d version i don't want to put them side by side because then it wouldn't be 2d but i

feel like i can put them top to bottom and it should still work and here it is so if i want a blue drink i cover this hole if i want a yellow drink i cover this hole and if i want a green drink i cover neither of the holes and for completeness here's the null drink similarly i could have a black coffee or i could have milk or i could have a milky coffee so that's how it works but why does it work why is it that putting your finger over different holes causes different liquids to flow out well it

comes down to surface tension it's similar to this demonstration you might have seen before look i can pull water from this bottle but if i turn the bottle upside down no water pours out the trick is that there's a gauze covering the opening of the bottle so when i pour it like this water can flow out and air can flow in but when i turn the bottle upside down for water to flow out air would need to flow in and for air to flow in surface tension would need to be broken here's another example whe

re instead of a gauze there's a small hole the hole is actually big enough to push a straw up into and it floats to the top of the bottle it's a really cool trick you know strictly speaking ultimately it's not surface tension that's keeping the liquid in place it's air pressure like the assassin's teapot and these bottle tricks wouldn't work in a vacuum so the reason the liquid doesn't fall out of the assassin's teapot when you have your thumb over the hole is because the atmosphere is pushing o

n it atmospheric pressure is holding the liquid in place and that's counter-intuitive like you think well the real explanation is that you know well if the liquid did fall out a little bit it would create a vacuum and the vacuum would pull the liquid back in but there is no pulling force there's only pushing force from the atmosphere it's like when you suck on a straw it's not the suction that's pulling the liquid up the straw it's the atmosphere pushing the liquid up the straw and that's really

counter-intuitive because you feel like well look that's me doing the work i'm i'm sucking on the straw i'm pulling the liquid up with my lungs at this point i want to go off on a bit of a tangent and talk about a type of pedantry that i think isn't always helpful like imagine you say i'm sucking liquid up a straw now i mean it's a weird thing to say out loud but hypothetically and then an annoying physicist comes along and says well technically you're not sucking water up a straw it's the atmo

sphere pushing it up the straw and then in the next breath that physicist might go on to talk about the flow of positively charged holes in a semiconductor well holes don't flow and a hole can't have a charge so why is it okay to talk about the flow of positively charged holes well the reason it's okay is because it's useful but i would also argue that it's useful to talk about a suction force so long as you keep the underlying physics in mind you should be okay like for example you can't just i

ncrease a suction force indefinitely eventually when you get to about 100 kilopascals it stops working because you've run out of atmospheric pressure the thing that's really doing the work underneath similarly i think it should be all right to talk about the flow of cold like if i put an ice cube in my drink the cold flows from the ice cube into the drink of course that's not really what's happening the warmth from the drink is flowing into the ice cube and so it gets colder but it's useful to t

alk about the flow of cold again so long as you understand the underlying physics like you can't just keep pumping cold into something because eventually you reach absolute zero by the way these animations are from a video i made about how all leds are secretly solar panels and all solar panels are secretly leds the link's in the card and in the description okay tangent over the point is we all know that for the water to get out air needs to be able to get in and with your finger off the hole we

ll i can get in at the top but if you cover over the hole the only way for the air to get in is through the spout and that's where surface tension comes in surface tension acts to minimize surface area you might think well one way for the water to get out is if the air can sneak past it on the way but what would that look like well it might look a bit like this you've got a drip of water starting on one side and on the other side you've got a bubble of air forming but see how that increases the

surface area of the water and because surface tension acts to decrease the surface area that's not energetically favorable and so you don't get this bubbling effect and instead the liquid is trapped inside the chamber this is also the principle behind a magic trick by the way sometimes called inexhaustible bottle or thinker drink it's usually a bit more elaborate it'll have more chambers and different options for drinks but anyway you can read all about it in my kids book sciences magic availabl

e for more good bookstores so these are magnets yeah and then these metal sticks magnets and then when they drive around they also go around with it and that makes it spin yeah and some of them go like this that was my daughter spontaneously explaining the mechanics of the thing that she just built the thing she just built was from a kiwiko project the sponsor of this video actually my kids have had a kiwiko subscription since way before they approached me for sponsorship so i can tell you a bit

about them it's a subscription service where a box comes in the post every month and everything you need for the projects is in the box you never need to run off to the shops or anything like that and the projects are stem projects there's eight different subscription lines for every possible age group you know something that i haven't talked about before that i really appreciate about kiwi co is the spontaneous stem discussions that arise from it you know i'm the sort of person who like a fact

will pop into my mind and i'll say hey kids did you know this thing about the moon you know whatever and you know it's completely out of context and the kids are sort of like well okay fine you know so these days i'm on the lookout for you know stem discussions that are within the context of what we're doing and kiwico is great for that because the kids are so invested in the projects already like they're building these things they're excited about them and then as you saw with the explanation

these stem discussions arise spontaneously and it's really amazing to see we've got a promo for the holiday season perhaps you know someone who would appreciate a kiwiko subscription in which case you can get the first month absolutely free using my special url if you go to kiwico dot com forward slash steve mold the link is also in the description so check out kiwi code today i hope you enjoyed this video if you did don't forget to hit subscribe and the algorithm thinks you'll enjoy this video

next so do you think the air is doing the same thing yeah you're saying that the air from the candle the candle is making the air push up on those red things now i see