This website requires Javascript to function.
During 2006, it cost approximately 5.7 cents per note to produce 8.2 billion U.S. paper currency notes.
top banner
Foothill Federal Credit Union
Earning MoneySaving Money is EasySmart SpendingBorrowing BucksFun & GamesWhat is a Credit Union Home Page
Would you rather


Castles are More than Walls

Like art and math? Then keep on reading to see where they mix!

Castles and forts were built for defense. The reasons for needing that defense ranges from wealth and showing power to protecting land and people. Castles aren’t just big walls and drawbridges, though. There’s math involved – both geometry and physics. So let’s look at the math of castles and how you can still use that knowledge today.


Castles weren’t built to look cool. It just happens that they do, in fact, look cool. Early castles were single towers; the height made them difficult to attack. Then the attackers started bringing ladders and siege engines—big rolling armored ladders.

The other problem with these tall towers was a lack of sightlines. The people in the tower couldn’t see their attackers! That was because these old towers were usually square, and it’s hard to see around a corner. To fix this, castle builders started adding turrets, the rounded towers on the corner of castles.

Building these turrets gave the defenders better angles to fire back at their attackers. The other advancement the turrets offered was more arrow slits. These are long, narrow openings in the walls that allow the people inside to see a large amount of the world outside simply by shifting a little side to side. But from the outside, those slits are extremely difficult to aim at.

This system of tall round turrets worked for a long time. The people inside could see the people outside. They had the angles to defend themselves no matter where the attack came from. But that all changed when gunpowder was invented, and cannons became a thing.


Tall, thick, stone walls are great for castles that need to defend against attackers who have arrows, swords, and the occasional catapult. But cannons changed the game. Here’s why…

Stone walls are subject to gravity, a key part of physics. The taller the wall, the thicker the base needs to be. Because of all the weight of the wall at the top, the stones at the bottom are under a lot of pressure.

Before cannons, attackers would often tunnel under walls and let the weight of the wall collapse the tunnel. This would then collapse the wall itself. Super dangerous. But cannons let attackers shoot into the walls without having to be under the wall.

Suddenly the geometry of the castle was more of a fault than a feature because of physics. So castle designers changed things up. Gone were the high, circular turrets; in were low, angular walls with arrowhead-shaped points coming out of the corners.

Now with the thicker low walls, often padded with dirt, the defenders were safer from cannon fire—the cannonballs just couldn’t break the walls. And the sharp angles let the defenders fire their cannons from more angles at the much less protected attackers!


The science of building things is called architecture. Architecture is science and art combined. Architects, the people who design buildings, want to make things that are cool and interesting. But they also have to make things that are practical and obey the laws of physics. So if you enjoy math and art, you might want to look into becoming an architect!

bottom slice graphic
Privacy & Internet Security Resources for Parents & Teachers About This Site