Ctesibius

File:ARAGO Francois Astronomie Populaire T1 page 0067 Fig16-17.jpg

Ctesibius' water clock, as visualized by the 17th-century French architect Claude Perrault

Ctesibius or Ktesibios or Tesibius (Template:Langx; Template:Fl BCE) was a Greek inventor and mathematician in Alexandria, Ptolemaic Egypt. Very little is known of Ctesibius' life, but his inventions were well known in his lifetime. He was likely the first head of the Museum of Alexandria. He wrote the first treatises on the science of compressed air and its uses in pumps (and even in a kind of cannon). This, in combination with his work On pneumatics on the elasticity of air, earned him the title of "father of pneumatics." None of his written work has survived, including his Memorabilia, a compilation of his research that was cited by Athenaeus. Ctesibius' most commonly known invention today is a pipe organ (hydraulis), a predecessor of the modern church organ.

Inventions

Ctesibius was the son of a barber, born Template:Circa BCE, probablyTemplate:Sndbut not certainlyTemplate:Sndin Alexandria.Template:Efn He began his career as a barber, following his father.

File:Hydraulis organ of Ctesibius.jpg

Reconstruction of Ctesibius' hydraulis at the Kotsanas Museum of Ancient Greek Technology, in Athens, Greece.

During this first career, he invented a counterweight-adjustable mirror. Another of his inventions was the hydraulis, a water organ that is considered the precursor of the modern pipe organ and the first keyboard instrument. He and his wife Thais were reputed to be highly-skilled players of the instrument. He improved the water clock or clepsydra ('water thief'), which for more than 1,800 years was the most accurate clock ever constructed, until the Dutch physicist Christiaan Huygens' invention of the pendulum clock in 1656. Ctesibius described one of the first force pumps for producing a jet of water, or for lifting water from wells. Examples have been found at various Roman sites, such as at Silchester in Britain. The principle of the siphon has also been attributed to him.

File:Ctesibius's water clock, 3rd century BC, Alexandria (reconstruction).jpg

Hydraulic clock of Ctesibius, reconstruction at the Technological Museum of Thessaloniki

Reputation

According to Diogenes Laërtius, Ctesibius was miserably poor. Laërtius details this by recounting the following concerning the philosopher Arcesilaus:

When he had gone to visit Ctesibius who was ill, seeing him in great distress from want, he secretly slipped his purse under his pillow; and when Ctesibius found it, "This," said he, "is the amusement of Arcesilaus."

Ctesibius's work is chronicled by Vitruvius, Athenaeus, Pliny the Elder, and Philo of Byzantium who repeatedly mention him, adding that the first mechanicians such as Ctesibius had the advantage of being under kings who loved fame and supported the arts. Proclus (the commentator on Euclid) and Hero of Alexandria also mention him.

Commemoration

• In 1976, the crater on the far side of the Moon was named Ctesibius by the International Astronomical Union.

Notes

File:A reconstruction of the counterweight-adjustable mirror of Ctesibius, Kotsanas Museum of Ancient Greek Technology.jpg

A reconstruction of the counterweight-adjustable mirror of Ctesibius in Kotsanas Museum of Ancient Greek Technology, Athens, Greece.