build the perfect marshmallow launching machine. This is a catapult model, and it would be

extremely dangerous if you were...this tall or like an angry squirrel.

And this model is inspired by the drawings of this genius. Leonardo da Vinci.

The same guy who painted the super famous Mona Lisa.

It's overrated, but still, pretty good. A catapult launches something in the air using

power from tension or gravity instead of using gunpowder.

There are different types — this one's called a mangonel. It's what you usually

think of. There's also a ballista — think of a crossbow.

And a trebuchet. This part is super heavy and the cow — I

mean the stone — you throw goes here. Then the stone gets released and the heavy stuff

helps shoot the stone up and out, like a big slingshot.

Catapults were invented in China and Europe around the 4th century BC. And it was actually

a breakthrough. They could launch big heavy stones at walls and enemies.

You could break through a wall with it. Did I mention we have cicadas here? Can you

hear the cicadas? In the 1300s, people said catapults were even

used to launch dead bodies over walls, because people wanted to spread the plague to their

enemies on their corpses. But Leonardo's catapult? It was as elegant

as one of his paintings. Bah.

Oh the first thing is to assemble the drum, let's go do that.

Today, Leonardo has a reputation for inventing things.

But when we look back, a lot of his inventions were just improvements on things that already

existed, like this drawing of a ladder to scale castle walls

He even made a few things that just didn't work. This helicopter looks awesome, but it

probably wouldn't fly. His catapults weren't some totally new thing.

He took tried-and-true elements from other catapults and made the design his own.

Our catapult is actually a mash up of these two drawings Leonardo made.

Let's switch to something that makes it easier to see exactly what Leonardo was thinking…

That's better. OK, so the drum and ratchet are gonna be how

we wind up the catapult. They're kinda like the charger to the battery that gives us all

the power. For this one, you turned the handle here to

wind up this drum, That winds up and pulls the rope, which pulls back the wood pieces

here. Now they hold a lot of energy that you used winding up the drum.

And that is pretty much how this catapult works too. See how when I pull this back,

the drum turns and pulls back these rods. All that tension lets it launch payload.

In our case, that's a marshmallow. In Leonardo's it would have been a large stone or some other

projectile that could just bash into castle walls.

In Leonardo's you probably wacked this thing here with a hammer to set the gear loose and

fire. In ours, you lock it by hooking this bar right

here to this gear. It stops it in place. That's taken from Leonardo's second design.

You wound the gear by sticking a bar in one of these holes and pulling everything more

taut over and over again. Then, see the bar that locks to a gear? It

holds the gear in place. That is what ours does too.

When we pull this release rope, the bar comes loose, the drum unwinds, and the catapult

fires. It's pretty easy. A good catapult can hold that tension for

as long as it has to. It requires all those elements to work in

tandem, and the person firing it to have the right touch. Which I do.

If one thing goes wrong — like right here, where the bar is out of place, the energy

is lost. And after a few tries, I believe that I will

be able to get this catapult to do something amazing — to fire the perfect marshmallow.

This is a crossbow Leonardo designed. See that dude there? That's how big this thing

was. And here's Leonardo's trebuchet and his

ideas for sweet shields to protect soldiers. He was a genius — he drew a baby in the

womb, and imagined a parachute, and made a crazy accurate overhead map.

But he was also a guy doodling in a bunch of different notebooks.

His catapult was probably never used in war. But his designs mashed together some really

clever ideas. People are still tinkering with the design

of catapults - this is being launched off a carrier by a kind of catapult.

And from looking at them, we can still be inspired to create a replica.

And I am no Leonardo, but that is something we can do too. We can adapt stuff. I'm gonna

attach this to the ground and make the release rope a little longer so that I can launch

it myself and get that sweet marshmallow arcing in the air.

That's something we all can do. We can't all draw, or instantly understand

physics, or get people to build weapons. But we can all imagine something amazing.

3! 2! 1!

You're 22 years old, Phil. Get it together! 3, 2, 1. Ow!