 Magdeburg hemispheres

The Magdeburg hemispheres are a historical experiment demonstrating the principles of air pressure and vacuum. They consist of two large brass hemispheres that, when placed together and sealed, create a vacuum between them. The experiment was famously conducted by German scientist Otto von Guericke in 1654. In the demonstration, a pump was used to evacuate the air from the hemispheres, making it possible to show the incredible strength of atmospheric pressure.