Ctesibius, also spelled Ktesibios or Tesibius (Ancient Greek: Κτησίβιος), lived around 285 to 222 BCE. He was a Greek inventor and mathematician who worked in Alexandria, Egypt under the Ptolemaic dynasty. Little is known about his personal life, but his inventions were widely recognized during his time. He may have been the first leader of the Museum of Alexandria. Ctesibius wrote early books about the science of compressed air and how it could be used in pumps and a type of cannon. His work on the elasticity of air, described in a book called On Pneumatics, earned him the title "father of pneumatics." No writings by Ctesibius have survived, including a book called Memorabilia, which was mentioned by a writer named Athenaeus. His most famous invention, the hydraulis, was an early version of the modern church organ. He was married to a woman named Thais, who should not be confused with Thaïs, a Greek woman who traveled with Alexander the Great.

Inventions

Ctesibius was born around 300 BCE, likely in Alexandria, and was the son of a barber. He began his career as a barber, following his father’s profession.

During this time, he invented a mirror that could be adjusted using weights. He also created the hydraulis, a water-powered musical instrument considered the earliest version of the modern pipe organ and the first keyboard instrument. He and his wife, Thais, were known for their skill in playing the hydraulis. He improved the hydraulis by using the weight of water to push air through the pipes instead of relying on falling lead weights.

Ctesibius also enhanced the water clock, or clepsydra, which was previously inaccurate because water flow could not be controlled properly. For over 1,800 years, the water clock was the most precise timekeeping device until the Dutch scientist Christiaan Huygens invented the pendulum clock in 1656.

He designed one of the first force pumps to create a jet of water or lift water from wells. Examples of these pumps have been found at Roman sites, such as Silchester in Britain. He is also credited with understanding the principle of the siphon, a device that moves water through a tube.

Additionally, Ctesibius is believed to have invented a catapult powered by compressed air, using his knowledge of air pressure. His inventions are known only through the writings of Vitruvius and Hero of Alexandria, who built upon his work for future engineering projects.

Reputation

According to Diogenes Laërtius, Ctesibius was very poor. Laërtius explains this by describing how the philosopher Arcesilaus spoke about him.

Ctesibius's work is recorded by Vitruvius, Athenaeus, Pliny the Elder, and Philo of Byzantium. These writers mention that early inventors like Ctesibius benefited from working under kings who valued fame and supported the arts. Proclus, a commentator on Euclid, and Hero of Alexandria also mention Ctesibius.

In modern times, Ctesibius is not as well known as some other inventors from his era. However, he is recognized for creating the foundation for future technological and engineering progress. He is called "the father of pneumatics" for his work with air pressure. His inventions have been improved and are still used in important ways today.

Commemoration

• In 1976, the International Astronomical Union gave the name Ctesibius to a crater located on the far side of the Moon.
• In 1897, a group of soft-bodied plant-eating beetles was named Ctesibius by Champion. This group includes one known species called Ctesibius eumolpoides.