 Hi everybody, thank you again if you're just joining us for Super Science Saturday brought to you by NCAR and UCAR Science Education Centers. We are going into our next event and again every 30 minutes we're going to have an awesome science show and next up we're going to travel through time and we're going to think about the physics of a medieval trebuchet. By the end of this event you'll be able to say trebuchet as well. So I'm going to send it over to Carl Drew's and as always you're welcome to ask us any questions throughout this event using the Slido platform, and we'll answer them as soon as we come back into 2020 but let's go to Carl Drew's, and we'll take it, take this, take it on. Welcome again to Super Science Saturday. My wizard persona is Zeus, the God of Thunder, and my hair here looks like a cumulonimbus cloud. And lightning comes out of cumulonimbus clouds and hail like you saw earlier and rain but I've turned it off for this demo so I don't scare all the mortals that are nearby. Now we mentioned we have a special treat for you today. We have a little time machine and we're going to go back in time to the, we're going to go back seven centuries to show you how the principles of physics were used to attack a Scottish castle. We're going to go back to the Scotland and the Scottish Wars of Independence. So let's roll that video tape. Here we go. Welcome to the year 1304. I am Edward I, King of England, and I have come to Scotland because the rebellious and proud Scots are rejecting my rule. I am laying siege to sterling castle with my mighty siege engine using the principles of weight and counterweight and physics to destroy the castle. And behold, the siege engine note is a trebuchet. I have pristened this one, the war wolf. It is 300 feet high and in its pouch it carries a 300 pound rock. It's designed on the principle of weight and counterweight. This long arm here with a comparatively light weight is balanced against the short end of the arm here with a heavy weight. When this is released, this drops, this raises up and a 300 pound rock flies into the air and smashes the Scots in their redoubt of sterling castle. The war wolf took me 50 master carpenters and three months to build. I am ready to show the Scots the might of my fist. All is now ready. Release the war wolf! Your Majesty, they're coming out of the castle. They want to surrender. What? What? You can't surrender? I spent three months building this war wolf, but I'm going to use it. Send them back to their castle. They will feel the might of King Edward. Release the war wolf! You destroyed my castle. I swear on the aggots I have for breakfast, I'll get you back one day. I think that means they've surrendered again, my lord. Very well. I accept their surrender. King was pretty uptight, wasn't he? Never mind, I am Zeus, god of thunder, lord of the sky, and I'm all about science. Let's take a look at King Edward's trebuchet, shall we? I think he was prone to exaggeration. Well, this baby is about 2-3 feet high and has a short arm here with a heavy weight, balancing a long arm with a much lighter weight, 300 pounds, he said. So this is the rock that goes in there, and what happens is normally this is in balance, but when this weight is heavy, this one is lighter, it will fly up and fling over the projectile over the top toward the castle. Let's give it a shot. Trigger mechanism is kind of tricky, but we hold it back like this in slow motion, and again. The trigger mechanism for trebuchet is kind of tricky. It consists of a pouch here on the end of a long string or rope, and it attaches to the end of the arm, like this. Pulled back at a sharp angle, but when the trigger releases, the weight swings out and unhooks from the arm, throwing the projectile out toward the castle. The problem is that this release point here is kind of tricky. In fact, the last use of a trebuchet in siege warfare was in 1521 when Cortez was besieging Mexico City. They released the arm of the trebuchet, its pouch swung out and released just as planned, then the projectile flew straight up into the air and came down, smash, and destroyed their trebuchet. And that was the final use of a trebuchet in siege warfare. And that is how the principles of physics with weight and counterweight were used in medieval siege warfare. I'm Zeus. Great to see you at Super Science Saturday. That was amazing. Thank you. Welcome to the year 2020. And thank you for the memorabilia that you've brought me, our writing utensil of the times. I appreciate that. It's good to be back. Yes. Well, I have to tell you, Lorena, that surrender really was refused. The Scots in the castle saw King Edward building this huge trebuchet and maybe taking a couple of practice shots toward their castle with these big boulders. And so they got scared and said, we're done. We're coming out. And he sent them back to the castle saying, no, I'm refusing it. I want to try this thing out. So that really did happen. And after he had destroyed the castle curtain wall, then he finally accepted the surrender. And I guess if there's any lesson for us today in that refusal of surrender is that we get very excited about our research and our science and the things that we're doing. And we love what we do, and we like to see it in action. And so you'll see that you already saw that in the demo earlier and you'll see that in the rest of the demos throughout the day. Yeah, it's so cool to see that, you know, there's scientists that were in the field, you know, with this catapult, like a lot of the, the weight and counterweight, like, you don't have to be inside the laboratory with like goggles and beakers, you can actually do science with pieces from a hardware store. Yes, you could build this catapult at home with, like you said, pieces from a hardware store. I'll bring it up here and I'll show you kind of a close up view of it and show you the parts of this. That's awesome. I'm so excited. Have you ever seen this trebuchet in action? Maybe you've seen it in cartoons, but it's actually historical, which is amazing. So there's a principle of torque, which is the twisting power here. So if I'm pulling on a short arm here, a short level, I have to push real hard. If I'm pushing on a long arm, I don't really have to push as hard. So the big rock here pushes against the lightweight over on this side and flings it over the top. Now there's a story about Archimedes, who said that if you give me a lever long enough and a place to stand, I can move the earth. So if we extend this principle, here's the earth over here on this side. Here's Archimedes, and he's over here giving it all he's gotten. He's pushing and pushing and sure enough, if he moves the lever a lot, the earth moves. Now there's a problem you never thought of is if there's an earthquake, and the earth moves a lot, then Archimedes is going to go flying off into space and hit the moon. Just like the Trebuchet showed. So you have to watch out for these kind of things, but it's the same principle of angular force, torque, and lever distances. Yeah, and I remember like, if I'm thinking of trying to move like my toy box, I can't lift it myself, but if I had like, you know, really sturdy, maybe a broom, and my adult at home could help me lift that. That's the torque that you're talking about. Yes, that's right. So if you lever it under something, you push real hard on it, you'll be able to move something much heavier than you are. Awesome. And I don't see that we have any questions yet. But if you are out there, and you wonder anything about weight and counterweight and torque, or maybe from where you traveled from, and that battle that you just had, like definitely let us know. And I'm seeing that we do have a few questions. Okay. Awesome. They have appeared. Thank you so much, Brett and everybody who's helping us and motive multimedia services during the Super Science Saturday to make this magic of technology happen. So we have a comment, the first comment where there were some flying shoes that you put these did you actually put them on the catapult. We put various items on the trebuchet and shot them. It's much better if the if something is smaller so it fits into the pouch so you have to adjust the pouch. But there are various things in medieval warfare that were catapulted over the city walls, kind of insulting things and dangerous things, not just rocks. So yes, that that did happen you can load anything in and away it goes. Wow. Let's see, and we have a question from T. Um, which is how big were the real trebuchets, how heavy slash big were the projectiles do you have an idea about that. Well T, I looked up this particular trebuchet was rumored to be 300 feet high, which is very, very high. So that's like a multi story building, you know what maybe 2530 stories. So that's very big and I think that had to be the height of the trebuchet with the arm extended vertical vertically in its rest position. So it's going to be up real high like this and so that's probably the height there. This one was, he really did take him 50 carpenters and three months to build and so he it was something really big. So it's a 300 pound rock with this thing which is also very, very heavy and so when that hits the wall, even a stone wall thick stone wall, it's going to destroy it and the story goes that he destroyed it with just the front of the castle but just a few shots there. So, perhaps as big as 300 feet high in its upright position and 300 pound rock so it's a lot of force. So thanks for that question T. Great engineering. And we have grace who's watching us so she just wanted to say hi, hi grace. Hi, everybody. Good to have you here. And Joe who said that was awesome. Thank you Joe, it was really a lot of fun to build this with my son Apollo up on Mount Olympus. Okay, and we have a question from Wallace. How do you aim the Trebuchet Wallace. That is the question that was very much on our minds as we put this together. The left to right is not so hard just you just aim the thing straight ahead and that's where it's going to go. But as the weight swings off the arm. You know when it's going to release. So you could throw something straight up in the air, or you could slam into the ground, or you could get a nice long shot. And I think what you have to do is do a lot of practice shots with the thing and adjust it and do it that launch it the same way every time, and you're going to get something predictable. So this is a principle in general science if you do things the same way and record exactly how you set things up, you're going to get repeatables results. And that's where we are most interested in science as being able to understand why we're getting the results we're getting. That's awesome trial and error. So many boulders that must have like flown through those time frames. Oh yes. That's an interesting question from Jenna. What countries use the tribuchet the most. Do you think I'm mostly familiar with European history and so it was used in England and in Scotland and in Germany to attack these fortified castles. The Chinese use things like this as well. And the Mongols use them in their invasions so this is really something throughout the world that's that's used. It's, oh, it's very difficult to attack a stone wall with just like spears and your bare hands so you got to find a way to throw rocks at big heavy rocks. And so, as long as they were fortified castles, people would come up with these things with various levels of success the one that Cortez used in Mexico City, it went straight up and destroyed his tribuchet so not very successful. Wow. Other questions. Yes, we have so many and it's so awesome, because everybody's really smart out there and they're they're really challenging us here. We expect. Yes, so we have a question from Paul, and they ask, what type of tribuchets are there. Well, there's there's three types. There's the one called the ballista, one called a manganelle, and the third one is called the tribuchet. The ballista is basically a giant crossbow. So you set up this apparatus. So there is this big bow or big members on the side that bend and you attach a wire or a cable or rope between them, and you pull it back with a winch. And then you can shoot either a giant arrow, or maybe a rock out and shoot it forward and then take maybe 20 minutes to load up the next one. So the speed of a ballista, the reef, the refiring speed is not very good, but it can really show something very powerful shoot this powerful like a big huge arrow out it's called the ballista it's a giant crossbow. What you find is called a manganelle, and that is where you have a arm like this rotating arm and it comes up against the stop. It's, it holds the ball here, or the rock here in a in a pocket, then it comes up and goes wham. And then you crank it down again with a big spring or ropes and then load it again and wham. And it throws the projectile out toward the castle that way. So that's called a manganelle that uses stored energy. The temperature is really the most powerful because you can make it as big as you can think of and this huge weight on top is the counterweight, and then throw something out this way. It also has the advantages is the arm doesn't come up against the stop plan, which is probably going to break your catapult. So this thing just sort of throws it smoothly uses a lot of the energy of the dropping weight and launches it out. When you get to high school there's classes you take about in physics, where you talk about kinetic energy and potential energy, and there's a trade off between potential potential energy and kinetic energy just like this, throwing something out that way. Those are the three types of ballista manganelle and attribute shape. That's so awesome. And it seems like each of them have their own, like, speciality so if something was flying in the air assuming we had dragons in this world. I feel like the ballista would probably do the most, you know, up in the sky shooting arrows. I think the ballista would be the easiest to aim. That's awesome. Thank you. And then we have Rue, who said, cool. Thank you, Rue. Let's see. Techo, Kai, and Amaya. Is it easy to make the trebuchets? I will show you how some of the things are made. I thought it was pretty easy, but you have to think out what you're doing first of all and plan how you're going to have the force there. This one here is made out of one by twos that Apollo and I bought at a hardware store, and then there's some braces on the sides. And this pouch here kind of looks like a face mask, but this is an actual pouch. And as long as you have a big heavy weight, this is what we use for a heavy weight. Does everybody have a sledgehammer head at home? I'm sure you do. You know, you've got a couple of these lying around. So that's a heavy weight that you can use. And just kind of put it all together. Get your mom, dad working with you. And you can make something like this and have some fun in your backyard. Awesome. So any adult at home with the, you know, that you trust can definitely help you to make that. That's awesome. And then we do have a question that's related to the trebuchets real quick before we get to a question that might be more of a science outside of what we're doing right now. But from Faye, are there still any trebuchets in any historical place? Or are there any remaining? At Stirling Castle, if you go to Scotland, Stirling Castle has been repaired since Edward broke it. And it is still a visitable place to this day. So you go to Stirling, Stirling Castle. The castle is there and they have a replica of the Warwolf Trebuchet there as well. So I don't know whether they throw stones every week, every month, or they just let it sit, but they do have a replica of this. So you can look at this and see how big it was in front of you and see this thing. And so yes, this is definitely a replica there in the historical place. There are some others as well. People build these things because they're a lot of fun. And they're also dangerous because they're very powerful. So people do build these and do historical reconstructions and you can find them in various places, probably in the United States as well. That's so awesome. And because everybody's kind of staying at home, there are a lot of things online that hopefully you can explore all the pictures, maybe Google can help you or any other platform of web searches until we get to travel again. And you're traveling through time like you are Carl. And which well that's a lot easier just go right where you want and the everything's all set up for you. Yeah, in our timeframe we, it must have gotten lost but we don't have that machine yet here. Okay, let's go to one that's about salinity of water and it might not be a question that you could answer but you know maybe somebody else throughout the day, or any other scientists as they go through Super Science Saturday might be able to answer. This is from Shamini Nath from India. Thank you for joining us. They say hello ma'am and sir. Good morning. I have a question. How does pressure affect, what how does pressure affect seawater salinity, and how does salinity react when the depth is changed. I'll tell you what I'll just address the other fact of salinity salinity makes seawater heavier, because a salt water is heavier so when you have a part of a part of the ocean that has a lot of salt in it, it will sink under the fresh water. The Mediterranean Sea is very salty, because a lot of evaporation happens there and so the water gets very salty. And so when that pours out on through the Strait of Gibraltar and out into the Atlantic Ocean, that heavy salty water goes down on the bottom and slides underneath the fresh water on top. And so at the Straits of Gibraltar you get this exchange where there is salt water coming out on the bottom and fresh water coming in on the top. So that's something that we notice in various places with salt water and that that it is heavier and more dense so it sits underneath the fresh water. Now temperature also makes a difference hot water is expands a little bit and is lighter. So if there's a combination of heat and warm water and cool water and salt and fresh water. It gets really complicated and we call that thermohaline circulation, where it's based both on salt and on temperature. Thank you so much for taking a crack at that and it's really cool to hear about how different temperatures and how salt water is a lot heavier so how temperature affects it as well. And again from Shamini and not from India, we, it's not a question but rather a comment. Sir, it's a great pleasure to meet you. I am one of the regular followers of the anchor activities. All programs are really appreciable and knowledgeable. Thank you. Shamini it's great to have you here we're really happy that you're watching us this morning, or whatever time it is in India. And we are coming close to the hour which is going to be close to the next event but one real quick question if you can answer. Pretty quickly is from Chechokai and Amaya. How fast can a trebuchet fling a rock. And I calculated how fast it could throw the golf ball that we are experimenting with and it was a few meters per second, which was enough to throw it about maybe 1015 feet or so. You could probably calculate that Edward stood off maybe a quarter mile from Sterling Castle and threw rocks all that way. And so using some of the principles that you learn in high school physics class. If you know how far something travels and how far it's thrown, you can calculate the speed. You don't have a way to measure that, but yes it can throw it fast enough to get it about quarter mile in the distance. So I'll just stop with that. Awesome thank you and I'm sure it has to do with the different size, how long the arm is so if anybody out there ends up making a trebuchet on your own. It's definitely a great science project. Oh yeah. Excel spreadsheet, use MATLAB, anything that will help you track that average speed for your own trebuchet. Well thank you so much Carl for coming to the year 2020 to share with us some historical information. I mean it's historical for us of course. Information about the trebuchets. And I look forward to continuing to see what is out there in the world of history and science. Good to have you with, good to be with you Lorena. Thank you for having me and bye bye everyone enjoy the rest of the presentations. Thank you everybody for joining us.