Vacuum engineering
Vacuum technology is a method used to evacuate air from a closed volume by creating a pressure differential from the closed volume to some vent, the ultimate vent being the open atmosphere. When using an industrial vacuum system, a vacuum pump or generator creates this pressure differential. A variety of technical inventions were created based on the idea of vacuum discovered during the 17th century. These range from vacuum generation pumps to X-ray tubes, which were later introduced to the medical field for use as sources of X-ray radiation. The vacuum environment has come to play an important role in scientific research as new discoveries are being made by looking back to the basic fundamentals of pressure. The idea of “perfect vacuum” cannot be realized, but very nearly approximated by the technological discoveries of the early 20th century. Vacuum engineering today uses a range of different material, from aluminum to zirconium and just about everything in between. There may be the popular belief that vacuum technology deals only with valves, flanges, and other vacuum components, but novel scientific discoveries are often made with the assistance of these traditional vacuum technologies, especially in the realm of high-tech. Vacuum engineering is used for compound semiconductors, power devices, memory logic, and photovoltaics.
Nothing
The idea that space can actually be empty was generally still not accepted by philosophers who invoked arguments similar to the plenum reasoning. Although Descartes views on this were challenged by Blaise Pascal, he declined to overturn the traditional belief, "horror vacui", commonly stated as "nature abhors a vacuum". This remained so until Evangelista Torricelli invented the barometer in 1643 and showed that an empty space appeared if the mercury tube was turned upside down. This phenomenon being known as the Torricelli vacuum and the unit of vacuum pressure, the torr, being named after him. Even Torricelli's teacher, the famous Galileo Galilei had previously been unable to adequately explain the sucking action of a pump.