# Why don't ships sink?

## From the road into the water: Why don't ships go down?

You have probably already wondered how ships hold up on the water, even though they are so incredibly big and heavy. Whether gigantic cargo ships that transport huge containers around the world, or super-fast motorboats: how can ships swim? Genius explains it to you!

The history of shipping goes back a long way. Before humans invented the wheel, the waterway was the best option for transportation. The ancient Egyptians built ships to sail on the Nile more than 5,000 years ago. As a building material, they initially used reeds that were tied together and later also wood.
Shipbuilding has continued to develop over the past millennia. The Vikings built their famous warships and the Spaniards large merchant ships out of wood. It was with such a merchant ship that Christopher Columbus discovered America in 1492. Today our ships are mostly made of metal. In contrast to wood, metal is very stable, but also much heavier.

#### How can a ship swim?

You have probably already seen a piece of wood floating on the water. And you also know that a metal ball goes down in water. Then why don't ships made of heavy metal go down?
Ships are hollow on the inside and have a bulbous shape. A crumpled ship would sink like the metal ball. Whether an object floats depends not only on its weight, but also on its shape. The shape of the ship creates buoyancy that keeps the ship on the water.

#### The Archimedean Principle

Another reason that ships can swim is the so-called "Archimedean Principle". The Greek mathematician Archimedes discovered this physical law over 2,000 years ago. You probably know that too: If you were to sit in a bathtub that was full to the brim, the tub would overflow. The water is "displaced".
The physical principle behind it says: The buoyancy of a body in water is sufficient if it displaces a greater weight of water than the body itself possesses. So if a 100-ton ship wants to swim, it has to displace more than 100 tons of water.

#### Swimming and diving: this is how submarines work

How is it that submarines can dive when they are hollow inside and filled with air? It's simple: submarines have large tanks that are filled with either water or air. The helmsman opens the tank flaps for the dive. As a result, the tanks fill with water and the submarine becomes heavier - it sinks. Deep-sea submarines can dive up to 6,000 meters deep. To get back to the surface, the helmsman fills the tanks with air from compressed air cylinders. The air displaces the water: the submarine becomes lighter again and the buoyancy stronger. The submarine floats like a ship on the water.

Post photo: Adobe Stock // STOCKSTUDIO

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