Although time and its measurement is a fundamental component of human life, a special type of clock which takes matters to the next level is the so-called astronomical clock and whose purpose is not to measure time per se but to convey astronomical information and, in particular, the relative position of the Sun and Moon as well as the zodiacal constellations and, in some cases, the position of the planets all as a function of time.

The oldest such effort to effectively emulate the overhead celestial sphere (ie a mini-planetarium) is the Antikythera Mechanism which was discovered in 1901 totally by accident by sponge divers off the coast of the Greek island of Antikythera. It has been dated to approximately 80 BC and it is believed to be the work of Poseidonius of Rhodes. The Antikythera Mechanism is currently on display at the National Archaeological Museum in Athens, Greece.

Note: The astrolabe is yet another instrument constructed to describe the overhead sky and monitor time. Some versions also have religious implications such as the Muslim Qibla where a magnetic compass on the back side of the astrolabe helps the user identify the proper orientation so as to point at the holy city of Mecca for prayer. Astrolabes were first developed by the Greeks around the second century BC and were slowly adopted throughout the known world of the time by numerous cultures. Astrolabes describe the position of the planets and prominent stars visible at a particular latitude (see curved markings on each dial in the photo below) and, by extension, act as time-keeping devices. Similarly, they assist in the time of expected sunrise which is vital for the Muslim religion and the timing of morning prayers at dawn ("fajr") and thereafter at noon ("dhuhr"), afternoon ("asr"), sunset ("maghrib") and nightfall ("isha"). As a result, it is no surprise that the overwhelming number of astrolabes found in museums around the world are islamic in origin given the adoption of these instruments from around 700 AD and thereafter by the Islamic World. Today's planispheres can be said to be a direct extension of the ancient astrolabe, for they function and inform the user of precisely the same information sought-after by users many centuries ago.

The brass astrolabe below is part of the collection of scientific instruments at Museo Torricelliano in Faenza. It is dated somewhere between the 16th and 18th centuries AD and, regrettably, the craftsman behind its manufacture is not known; a common characteristic for many Latin and Italian astrolabes which has haunted historians and researchers. The astrolabe represents a gift to the museum by conte Luigi Zauli Naldi who frequently gifted works of art to various museums in Faenza. The astrolabe is accompanied by four tympanums serving latitudes 38°, 41°, 45° 40' and 47°, has a double arm rule and the rete is characterized with approximately 26 star pointers. What is worthy of note is the mater which is attached to a square brass base. All inscriptions are Latin with the outer ring of the astrolabe describing 24 hours in two 12-hr segments and which is very typical of Italian astrolabes. As noted, the astrolabe is accompanied by four (latitude) plates, thus being planespheric in nature, for it projects the three-dimensional celestial sphere onto a two-dimensional plane. During the Middle Ages, three-dimensional astrolabes were first described but only one such example seems to have survived to present day and which can be found at the History of Science Museum in Oxford, England (travel and photography forthcoming). It should be noted that the astrolabe below should be rotated 90 degrees counter clockwise so as to be in its proper "home" position.

Museo Torricelliano in Faenza is named in honour of Evangelista Torricelli (1608-1647 AD), an Italian physicist and mathematician, who is perhaps best known for having invented the barometer and for whom units of pressure ("torr") are named after. Not only were his parents from Faenza but he would study in the city during his formative years and would eventually continue in Rome including a period under Galileo Galilei's tutelage. The museum is open on Saturdays between 09:30 and 12:30 and its collection includes a variety of scientific instruments from the 17th to the 20th centuries as well as the impressive astrolabe below, various telescopes and quadrants. Within a few minutes away, one will encounter La Paestra della Scienza ("The Science Gym"), a wonderful mini science museum and where young high school students are exposed to such key topics as astronomy, physics, chemistry, optics and mathematics, thus making an early impression upon them about the beauty of the scientific world and its methods via experimentation and observation.

Note: For additional results involving astronomical clocks and astrolabes (including astrolabe quadrants) from around the world, please click here.