HomeboyMediaNews

The Astrolabe of Antikithyra January 21, 2007

One of the most impressive things found in this period was the Astrolabe of Antikithyra.

Some sponge collectors found it in 1901 near the Antikithyra island. In the Greek Research Centre ‘Demokritos’ professor Derek de Solla Piere, from Yale University, and Har. Karakalos examined it with X-rays and found an amazingly complex construction. It is the most complex mechanical construction until 1200 A.D.

  The function of a common astrolabe is to measure the altitudes of celestial bodies, from which time the observer’s latitude could be determined, too. The measurement of the altitude of the North Star yields the latitude and the altitude of the Sun and stars yields the time.

The instrument fount at Antikithyra has a lot of metal wheels arranged in a way that simulates the movement of the stars and does the required calculations. Who designed it and who made it with such accuracy remains a mystery. But it is clear enough that is not an astrolabe but a kind of astrological calculator.

In the astrolabe there were 27 different circular gears that were connected all together and were put into movement by a hand shaft. Everything was inside a wooden box with possible dimensions of 35 x 17 x 10 cm. On the front face there were two disks with indications about the date of the month according the sun, and the date according the moon. On the back face there were two other disks, one showing the moon month and the other the moon eclipses. Maybe these things seem simple but if you want to calculate them be prepared for calculations with six-decimal-digit accuracy.

  Reconstruction of the mechanism by professor Derek de Solla Piere

Another technique appeared on the astrolabe for the first time in the history of engineering was the use of the differential gear. The rotation speed of the in shaft equals to the difference of the speed of the two output shafts. Nothing like that reappeared in any known machinery until 19th century. The differential gear was used on that Astrolabe in order to allow the connection of sun to solar eclipses.

The astrolabe was probably first used by the ancient Greek astronomer Hipparchus.* Some people say that Archimedes has used some things like this, but a lot different from what it is found.

*Hipparchus discovered the precession of the equinoxes. His calculation of the length of the year measured by the sun was within 6.5 minutes of modern measurements. Hipparchus devised a method of locating geographic positions by means of latitudes and longitudes. He catalogued, charted, and calculated the brightness of perhaps as many as 1000 stars. Hipparchus also compiled a table of trigonometric chords that became the basis for modern trigonometry.

Ancient Greek Technology January 21, 2007

Who said that the robots, the automatic doors and the locomotive are technological advances of the second millennium? Definitely not!

The pieces of information that keep surfacing prove what has been, for some decades, common knowledge among researchers: in Ancient Greece, people like Daedalus and Gods like Hephaestus developed techniques and operated inventions that a lot of inventors of our days would have been proud of.

Talos > The famous Talos, in the ancient Cretan dialect it means sun, was a fully operational robot, built by Hephaestus as a gift for Minos, King of Crete. Talos was made of copper and was huge. It protected Crete from her enemies and supervised the application of laws. It could move very fast and was capable of touring Crete 3 times in a single day, medium speed 250 km/h! It had the power to throw enormous rocks against his opponents or to burn them with his boiling hot breath. In this way it drove back the hostile boats, protecting the island.

According to tradition, when the Argonauts returned from Kolhida, they managed to destroy Talos with the help of Medea, the witch.  Medea used her forces to confuse Talos and the Argonauts wounded his leg. The blood pumped out of his one and only vein as melted metal. An other version of same story reports that Poias, father of Filoktitis, aimed an arrow to Talos’ heel, a screw came off and the blood of Gods streamed from the metal body. Many coins, picturing Talos were found in the city of Phaistos.

Automatic doors > Ancient technology was naturally placed in the service of religion. When a believer was making an offertory to a God, the God should thank him, no matter the hour of the day. Otherwise, perhaps the believer would turn to another God, there were many at those days, and some priests would loose the “benefits” of servicing their God. So, with the help of technology, certain doors opened automatically when the fire was lit on the altar and even certain statues began moving.

It is said that Heronas and Ktisivios had constructed mechanisms that sounded the trumpets of a temple when the altars were lit. The interior of temple was sprayed with scented water, metallic birds began singing and some statues began flying. It is also said that the lighting conditions in and around the temple were regulated, creating artificial fog, when necessary.

Heronas’ steam engine > Heronas of Alexandria was a Greek mathematician, engineer and inventor of the first century BC. He initially worked as shoemaker but he eventually decided to explore his ideas. He is better known as an engineer for his hydraulic mechanisms, simple machines and automations, but he was also an important mathematician of his time. He served as a director of the famous Technical School of Alexandria, maybe the world’s first polytechnic university.

He presented and operated the world’s first steam engine, consisted of a closed, spherical container, filled with water. When the water was heated and began to boil, the stream was relieved by two nozzles, configured in a polar alignment. The container was fixed in such a way that was allowed to rotate. The steam release caused a rotating motion of the container that could be used as a steam motor for various applications. The principle of this simple configuration is the same used today for jet propulsion.

Air and water pumps > Ctesibius (fl. 2nd century B.C.), a Greek Alexandrian, was described as a mechanical genius whose inventiveness was limited only by the restrictions of the world he lived in. He was the son of a barber but the highly technical environment of Alexandria of this time helped him to leave the barbershop soon.

Using the power of water and air, he devised a number of ingenious mechanisms: a water organ, whose air pipes were operated by the weight of falling water, an air-powered catapult and a force pump. Another useful invention was a portable double water pump used by the firemen to put off the fires on the big buildings of his city.

Ctesibius is perhaps best remembered for the clepsydra, or water clock. Although he did not actually invent it, he greatly improved it. Ctesibius liked music and had an idea of using waterpower for his music creations. He made the first ‘armonion’. This was pumping air through pipes.

Talking about musical instruments, it would be an omission to not mention Pythagoras. He meditated the relation of the music to the mathematics and found some rules that make the making of musical instruments much easier. He managed to express the musical harmony with mathematic rules through his philosophical and scientific approach.

The piston pub was also used by Ctesibius to pump water or air. He used it mainly for his prototype ‘armonion’ but also to other machines. These pubs were used in many constructions since then. They can pump water or air depending on the accuracy of the construction. In many applications we can find them in use until today, because of their simplicity and their reliability.