Otto von Guericke (1602-1686). 1891 illustration of the German engineer and physicist Otto von Guericke with the first electric friction machine. Guericke carried out research into the existence and nature of vacuums. He devised an air vacuum pump and used it to show that sounds cannot be heard in a vacuum and that flames are extinguished. He also showed that when two large metal hemispheres (the 'Magdeburg hemispheres') were placed together and the air within was pumped out, they require great force to separate them. Illustration from 'Physique Populaire' by Emile Desbeaux.