Astral Complications

gears of timeThis is not an article filled with new-age relationship jargon; it is about machines. Human ingenuity, starting from simple stone blocks, has developed means of making gears and springs that tirelessly calculate various astronomical functions, without the assistance of digital chips or electricity. That’s what Astral Complications are all about.

“Complication”, as used in this article, is a horologists’ term for any function of a clock or watch that indicates something other than hours, minutes and seconds. Although the definition includes electronic and digital watches, I will not be discussing those: my topic is the purely mechanical solutions for the problems of astrophysical timekeeping.

Two of the earliest mechanical solutions for keeping up with the cycles of time are the Minoan Calendar Stone and Stonehenge. The operation of Stonehenge as a calculator for the cycles of the Sun and as an eclipse calculator have been somewhat described in my article called “Are You Eclipsed?”, and will be the subject of a future piece on this wonder of Neolithic technology.

The Minoan Calendar Stone, which Scottish author Richard Heath calls the “Disk of Kronos” was designed to measure time from the simplest unit, the day, up to the synodic period of Saturn. It consisted of one ring of 63 holes, representing 1/6th of the Saturn Synod. The next ring consisted of 15 holes, which represented the 15 to 16 ratio of the Moon to Saturn cycle. Although the details are far too numerous to go into here, let’s just say that through multiplication by whole numbers, the length of eclipse seasons, the Lunar Year and the cycles of Jupiter can easily be mapped out.

The seven waves in the center represent the days of the week, which would be natural for those using this “calculator” because the cycles of Saturn are evenly divisible by 7, as is the Lunar Month, which, when realized as a 28 (4*7) day month, 13 of which equal 364, the basis of the “year and a day” season so familiar to mythologists and anthropologists that study matrilineal cultures.

According to Mr. Heath, the calendar stone describes the adoption of the 7 day week throughout Mesopotamia, Egypt and the pre-classical era Greek world; it appears to be a historical reality. Because of the Minoan trading routes, it may even be the origin of the Jewish 7 day week. At any rate, it is the only evidence we have of its origin; the Solar year of 365.25 days fits into this scheme only by way of the eclipse year and season, which required greater effort to track.

antikytheraThe most fascinating of all astro-mechanical devices is the Antikythera Mechanism. This device, discovered in the Mediterranean and dated at being over 2000 years old, has been the subject of all sorts of conspiracy theories. But the fact is that careful studies have been able to prove that the gears were constructed in ratios that correctly matched the Solar and Lunar cycles, as well as the synodic and orbital cycles of the planets, such that by winding a crank, the correct positions of the planets, as well as the dates of eclipses and other phenomena could be found. In other words, it was both a mechanical clock and an astrological computer. There have been more than one reconstructions of this incredible (and incredibly ancient) device; my favorite is the one created by VanVark.

Apparently, the knowledge that created this device was lost at some point, because we don’t see any similar machines until much later, and they were more concerned with keeping “ideal” time than “natural” time. At this point, we need to look at more modern devices in order to understand the history of how these marvels developed.

By the definition of Horologists, complications fall into two distinct categories depending on whether or not they are related to measuring time. The complications not related to timekeeping that have been placed on wristwatches include barometers, compasses and, as you may have seen on a mechanical pilot’s watch, an altimeter. Complications related to timekeeping include the following categories:

Acoustic complications

  • Time SignalAlarm
  • Repeaters (hour, 15 minutes, minute, etc.)
  • Chimes (grand sonnerie and petit sonnerie)
  • Silencer (to dampen the sound of the movements)

Measures of short time

  • These are the chronographic and other split-second functions, and those scales and such that serve to make tachymetric or telemetric measurements

Common, or everyday complications

  • World and universal time
  • Multiple time zones
  • Diving dial
  • Tide gauge
  • Power reserve indicator

Precision and convenience complications

  • Self-winding
  • Tourbillon

Astronomical (astral) complications

  • Simple calendar (full or partial)
  • “Perpetual” calendar
  • Week number
  • Year
  • Equation of time
  • Sunrise and sunset for a given location
  • Phase of the Moon
  • Sidereal time
  • Declination of the Sun
  • Apparent movement of the planets
  • Line of the Moon’s node
  • Star chart for a given location

As you can see, these complications can perform most astrometric functions mechanically.

tourbillonThe Tourbillon is essentially a gravity compensator. It was designed and patented by Abraham-Louis Breguet in 1801 to correct errors of rate caused by the effect of Earth’s gravity on the movements and gears of a watch.

It consists of a revolving cage with a balance (called a regulating organ by experts) at the center. The cage revolves about once a minute and compensates for the errors of rate caused by the vertical position in which pocket and wrist watches are usually found. The Tourbillon will even adjust the watch mechanism for the slight difference in gravity between the poles and the equator.

This type of ingenious error correction is absolutely necessary for astronomical calculation of any reasonable precision, yet it is found in only a few astrometric watches. The idea of power storage in a mechanical watch, which is based on physical monitoring of the tension of the mainspring, is fascinating enough, but this device is truly a testimony to the ingenuity of engineers and watchmakers.

Astronomical watches have a lineage that dates back to the great astronomical clocks of the 14th and 15th centuries, and the pocket watches of the Renaissance. The minute hand, a late 17th century innovation, was not used at the time, but these watches displayed the hour, date, day of the week, months with their duration, moon phases and the signs of the zodiac. Their roots were in 13th century Islamic astronomical and chronological computers, which researchers believe were based on the Antikythera mechanism mentioned above.

One of the most important factors in making the correct astronomical calculations is the equation of time. It enables us to tell the difference between “true” solar time, as it exists in nature, and “mean” solar time, which is our convenient 24 hour day.

vctiAs the Earth makes its elliptical orbit around the Sun, its axis is tilted away from the plane of the equator. Consequently, the length of a day counted by the interval between two astronomical noons (when the Sun is at its highest point in the sky) varies throughout the year. This difference is 24 hours long on only four days during the year. All other days are either longer or shorter, and the difference, which can be from (approximately) -16 to +14 minutes is calculated by the equation of time.

A precisely made cam that completes a single rotation in a year mechanically programs the equation, but the trick is in displaying it. Some watches have a hand that moves from -16 to +14 on a small dial, but that requires a bit of mental juggling in order to know what the true solar time is. The more complex watches have two minute hands, one showing the true solar time and the other showing the common mean solar time. This complication is called the  équation marchante, or running equation. The first type can be seen on the reverse face of the $1.4 million Vacheron-Constantin Tour d’Ile on the left.

ppsmsSidereal time is measured by the rotation of the Earth around its axis as measured against the background of the fixed stars. A sidereal day is approximately 4 minutes less than a mean solar day of 24 hours, and is indispensable for astronomical/astrological calculations. The skeletonized hands on the back of the Patek Philippe Sky-Moon Tourbillon on the left measure Sidereal time. One was auctioned off in June of 2007 a mere $1.2 million, but only two are made per year, so you may not be able to find one at any price.

Other features of the Sky-Moon watch above involve an accurate image of the celestial sphere and exact lunar period measurement, enabling the owner to precisely know the lunar “age” and calculate the various Solunar phenomena. But there is another set of astral complications that have been executed in the luxury watches of Ulysse Nardin.

acomp2On the right, we have the Planetarium, which (outside of its timekeeping hands) consists of a series of concentric rings that represent the orbits of the visible planets around the Sun. The Earth jewel has an auxiliary hand that represents the movement of the Moon in its orbit. This is a picture of the solar system from the heliocentric perspective. Through a clever set of constructions, you can also find the geocentric positions of the planets. This enables one to view both the Copernican and Ptolemaic models of the solar system.

acomp1On the left, we have the Astrolabium, with which one can calculate the rising and setting of stars and planets, predict eclipses, navigate by the stars and so much more. This watch has a power reserve of 42 hours, meaning that it only has to be wound about every two days if it is not being worn, because it is a totally mechanical self winding device.

Here we have seen only a few examples of these brilliant mechanical solutions for astronomical problems. The next article in this series will cover non-portable mechanical calculators used by astrologers and astronomers; the Orerry and the Antikythera.

© Roy Kirkland 2007