Prague Astronomical Clock

One of the nice things about living in Europe is the abundance of artifacts and places of astronomical interest...amidst all the culture and history you would expect to encounter traveling and visiting different cities and countries, one finds that they eventually run across a historical attraction which piques the interest for those of us who have a passion for astronomy. Today we visit the city of Prague (about an 8-hour train ride from my residence in Krakow Poland) and look at the Astronomical Clock in Prague.

Prague Astronomical Clock.

The Prague Astronomical Clock is built into the facade of Old Town Hall in Prague and is believed to have originated around the year 1410. Various modifications, upgrades, and reconstructions have occurred over the centuries (the details of which could be a whole book in itself), but what I found particularly interesting was the wealth of data they were able to convey from the gears, pulleys, and flywheels of the clock.

When viewing the Astronomical Clock we can see time on four different scales:

• Old Czech (Italian) Time: Marked on the outer "24-ring", a new day is counted by the setting of the sun.


• German (Local) Time: Marked by Roman numerals on a disk inside that of the outer ring.


• Planetary Time: Measured from the rising to the setting of the sun, used in astrology.


• Sidereal Time: Shows the current position of the starfield above, indicated by a star on a zodiac ring.

Other useful astronomical information can be derived from the clock as well:

• The height of the sun and the moon above the horizon is shown throughout the year.


• The rising and setting of the sun and moon are shown, as well as the current phase of the moon.


• The astronomical night is indicated (when the sun dips 18 degrees below the horizon).

Along with the useful astronomical data on display we also have a number of features of purely artistic or religious purposes, most notably:

• A number of carved wooden figures stand aside from the clock. When the clock hits the top of the hour and the bells chime, the figures animate and move - the most interesting of these is the skeleton which pulls the rope that chimes a bell, and he (she?) turns an hourglass over, a symbol of the passing of time.


• Also at the top of the hour when the clock chimes two shutters above the clock open and figures of the twelve apostles appear in the windows briefly.

You can see the clock in action below as the top of the hour is reached:

It was enlightening to discover what our ancestors were capable of without the use of modern computers and technology!