Modern submarines are sleek cutting-edge marvels of engineering, capable of staying underwater indefinitely at depths of more than 800 feet and launching missiles from hundreds of miles away. But submarines have been around for a lot longer than you think.
Leonardo Da Vinci is considered the inventor of the submarine: He made a sketch and wrote about the possibilities of underwater travel in the late 1400s. The first article on the science of submarines was published by an Englishman in 1580, and by the late 1600s inventors were creating drawings and making prototype submarines all over the world.
There is one technology used on submarines that is even older than Da Vinci's ideas: the periscope. A periscope lets you see over things that you may not be tall enough to see over, such as fences, walls or even other people.
Johannes Gutenberg was a blacksmith, publisher and goldsmith. He is best known for the invention of the first printing press, which led to the mass production of books and the first method of mass communication in the world. But in 1430, he also invented a primitive periscope for people to watch religious ceremonies while standing in large crowds. Hippolyte Marie-Davie, a French inventor who first imagined submarines could be driven by electric motors, created the first periscope for naval use in 1854.
A periscope is made from a long cylinder and two mirrors. The mirrors are placed at the opposite ends of the cylinder at 45 degree angles from one another. When you look at the mirror at the bottom of the periscope, you see a reflection of the mirror at the top of the periscope, which is looking outside the tube. A submarine can dive dozens of feet below the water to hide and raise its periscope a few inches out of the water to keep an eye out for enemy ships without giving away its position.