The Magdeburg hemispheres are a famous demonstration of atmospheric pressure, invented by the German scientist Otto von Guericke in 1654. This experiment involved two large copper hemispheres that could be evacuated of air, creating a vacuum between them. When the air was removed, the external atmospheric pressure was strong enough to hold the hemispheres together, making it difficult for teams of horses to pull them apart. This experiment illustrated the power of atmospheric pressure and helped to advance the understanding of vacuums in science. The Magdeburg hemispheres remain a significant historical example of early experimental physics and are often used in educational demonstrations today.