Astronomical Clock in Prague

The Astronomical Clock in Prague

By Cassandra Santiago


The Astronomical Clock located in Prague was made in 1410 by Mikulas of Kadan and Jan Ondrejuv.  The clock showed exclusive astronomical data. This clock is one of the oldest European clocks of its time.  All of the functions of the clock are still working to this day. This clock includes three features:

The figures of apostle were an addition to the clock in 1865-1866.  The figures pass through two windows on the clock every hour, on the hour during the daytime.  Other figures begin to move at this time.  One of the figures that move is Death holding an hourglass and he beckons a Turkish man, who shakes his head.  There is a statue for Vanity, which is a man holding a mirror.  Another statue represents Miserliness.  This statue is holding a moneybag, shaking a stick.  The Astronomer, a Chronicler, a Philosopher, and an Angel.  The moving apostles are located next to the astronomical dial while the apostles that aren't moving are located next to the calendar dial.  When the apostles are finished their journey, a golden cockerel that is located at the top of the clock crows and begins to shake it's wings as the clock chimes the hour. 



The next feature of the Astronomical Clock is a Calendar Dial.  This is the newest addition to the clock.  In the center of the dial is the Old Town Symbol.  On the outside of the dial, every day of they calendar year is represented and the date is shown at the top.  There are also twelve medallions, representing the twelve zodiac signs.





The last part of the clock is the Astronomical Dial.  This part of the clock depicts the way the universe was thought to be in medieval times.  The Earth is located in the center.  There is a blue part on the dial that represents the sky above the horizon and a brown part that represents the sky below the horizon.  There is a Zodiac ring located on the dial.  It exemplifies the stars and moves according to it.  There are two clock hands on the astronomical clock.  One hand bears the signs of the Sun and the other bears the signs of the Moon. On the dial, there are three circles.  Each circle a different time.  One shows the Old Czech Time in Schwabacher numerals.  Another shows Central European Time using Roman numerals.  The most inner circle shows the Babylonian Time using Arabic numbers.  In Babylonia, the length of an hour differs depending on the season.  This clock is the only one in the world that can measure it.  There is a little star located near the zodiac ring that shows sidereal time.  

There are three co-axial wheels that are the same size.  All three are driven by the same pinion but have a different number of cogs (365, 366 ,379).  One of the wheels gears the zodiac and rotates once ever sidereal day.  A sidereal day is about 4 minutes less than a regular solar day.  The second wheel gears the indicator of the Sun and it rotates once every solar day.  The third one gears the Moon's pointer and moves with the apparent motion of the Moon.  There is also a ball that is half silver and half black.  This indicates the phase that the Moon is in and rotates every sydonic month.  




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