Section 2- Lots of Time

The Spilhaus Clock and its Functions

By Dr. Athelstan Spilhaus

It is most important to understand that all of the time and position measurements of the sun, moon and stars are subject to many and complicated effects, due to the interaction of every astronomical body on every other body. In order to present this eternally moving rhythm of the universe in a relatively simple manner, it is necessary to simplify the presentation and to deal only with the average or mean time and position of each of the heavenly bodies in which we are interested.

The only perfectly regular basis of time is our man-made clock, automatically and synchronously driven by 60-cycle electrical current, or by well adjusted watch movements, etc. These are quite regular since they are almost wholly uninfluenced by external forces.

It is entirely different with the heavenly bodies in the universe around us. The sun, for instance, arrives at its south meridian at high noon within a range of perhaps plus or minus 15 minutes. Most people never know of this, but astronomers do. The same is true of any of the stars.

The moon is so greatly influenced that it shows variations of a much greater amount. The tides are influenced not only by these variations in the moon, but also by the sun and by geographical patterns on the earth.

It is obvious that the best presentation of this kind of variable information must be that of the mean values which can then be more consistently related to the steady routine of our man-made clocks. In this sense, therefore, we will proceed to describe the individual functions of the Spilhaus Space Clock.


The complete story of the movement of the sun, moon and stars is continuously displayed on the large Space Dial (see page 4). Whether or not one of these bodies is actually visible to you, in the night sky, depends upon whether it is inside or outside of the horizon, repesented by the fixed, light blue ellipse area (see Horizon and Hour Disc B, page 9) which is in a fixed position at 40 degrees north latitude. The horizon at 30 degrees north latitude is marked in part by a dotted line, and the rest of the curve locates approximately in the position of the hour numbers, 11, 12, 13, etc. This is an area of some inconsistency as to visibility and, therefore, it is not shown as a sharp limitation. For those at say 50 degrees north latitude, an approximately equal shift on the other side of the 400 line can be easily imagined. It is most important to note that all of these curves are close together in the east and west positions where it is of most interest since the rising and setting phenomena occur in these regions. You will see the stars either rising on the eastern horizon, at their zenith on the north- south line and setting on the western horizon or continually visible near the pole star.


The golden sun moves around in its 24-hour mean time orbit, in a counter- clockwise direction, coming regularly to its South meridian position, which is also marked as 12 o'clock noon. It enters the curve at the right or East, moves across to the left during the daylight hours, and sets in the West at the left. During the night hours, the sun's image on the sun disc travels outside of the horizon circle and, therefore, is not actually visible. It is, however, still in motion and it sweeps down, under and up again to a new dawn.


The moon also sweeps through the visible heavens within the horizon circle and passes down under, and up again much like the sun. The relative positions of the sun and moon are continuously changing, but their patterns of movement are similar.


The star field moves in the same general manner in a counterclockwise direction relative to the visible area within the

horizon line, and the individual stars each behave in a manner quite like that of the sun and the moon, but with individual differences as explained later.


These positions are constantly changing, and the Space Clock continuously shows these changes with remarkable accuracy by the relative motions of the sun, moon and star discs which contain these bodies.


The gold line through the sun has to be set initially at the proper calendar day, and the clock automatically advances by one calendar day every 24 hours. Thus, it shows you the correct date and month throughout the year. Every fourth year on February 29, you must set the Star Disc back one day (leap year). All of the moving discs rotate together counter -clockwise at an approximate rate of one revolution in 24-hours. Only the Sun Disc rotates at precisely this rate. The other 3 moving discs each have slightly different speeds of rotation. The star disc is slightly faster and this advance is exactly a one day mark on the calendar circle every 24-hours, thus giving us the calendar indicator movement.


The difference between solar time and our standard zone time, which is displayed by the lower left clock dial, is due to the artificial use of zone time as our ordinary time. (See pages 27 and 28 for an explanation.) The sun actually appears to move quite regularly across the face of the earth and it gives to each position on the earth as it passes directly overhead, an instant of being at its zenith or of crossing the meridian for that particular point on the earth's surface. This is a natural phenomenon and, for the observer of the Space Clock for a given geographical location, there is thus determined the one and only time of the zenith position of the sun at that location. It is this time to which the sun line must be set, and read against the 24-hour numbers on the large dial. Relative to this true sun time, the standard time of an entire geographical zone will be different by an amount as much as plus or minus 4-0 minutes. This correction must always be kept in mind when any of the information displayed on the large Space Dial or on the World Time Dial, is to be interpreted in terms of either standard or daylight zone time to which we are accustomed.

We have, therefore, to think of the time relations of the sun, moon and stars always in terms of this solar time which is established by the exact longitude of the location of the clock. The sun is the pacemaker and goes around exactly on the hour schedule shown by the gold numerals on the fixed Horizon and Hour Disc, reaching its meridian at 12 hours on this scale.

The moon, and each individual star, likewise arrives at the meridian position of south according to its own time schedule. The south meridian is shown at top center and corresponds in position with the 12 hour mark. These two are coincident only for the sun. When the line of the moon reaches the south meridian point, the time at this instant is read between the sun line and the gold hour numerals. Similarly for each star which, by projection of an imaginary radial line, would reach the south meridian position at an instant of time, this time would be given only by the sun line and the hour markings.


As previously mentioned, this is use I principally by astronomers. It is told by the light blue arrow at the September 23rd position, and is read on the gold hour scale. Star time differs from sun time all throughout the year except on one day, September 23rd.


The phase of the moon is due to the physical position of the sun, the moon, and the viewer on the earth. The sun is always illuminating one-half of the moon, but as the relative positions of the sun and moon on the Space Clock change during the lunar month, the phases of the moon's appearance can be easily explained if one assumes his position to be at the center of the dial and he looks toward the moon and sees that portion of the moon illuminated by the sun. To indicate the 4 quadrant positions in this continuous movement, there are shown the conventional 4 quarters in light blue. For instance, full moon occurs when the moon is diametrically opposite the sun without regard to the direction in which this diameter extends. This means if the sun is visible within the light blue horizon ellipse, then full moon actually occurs when the moon is ''down under" and out of sight. An opposite condition would be when the sun is in the nighttime and the moon is diametrically opposite and visible.


The variation in this phenomenon is on an annual basis and so it can be shown by markings on both the Sun and the Star and Calendar Discs which, between them, have a once-per-year rotation. Therefore, the gold curve which is almost like a circle, has been carefully drawn to show, in conjunction with the scales for sunrise and sunset, the time at which these occur. Obviously, sunrise and sunset throughout the year depend also upon the latitude of the observer. Two scales have been calibrated, one at 300 and the other at 400 north latitude. Estimates can be made for other latitudes. As a result, the hour of sunrise and the hour of sunset, for the current day, is read from the intersection of the gold circle and the two gold, straight-line, opposing scales, with suitable estimates for north latitude correction. The hours thus obtained are always in terms of solar time, the only true time, and must therefore be further modified to be interpreted as either standard zone time or daylight saving zone time which, again, is an arbitrary matter.


The complications in this case are too great to show in dayby-day changes, and the mean time is indicated in the following manner. Physically, the moon enters and leaves the visible horizon at times which are so variable that it is impractical to show them without extra-ordinary complications. We are constrained to emphasize the importance of the time at which the moon reaches its "South" zenith position, which is obviously the mid-point in time and position. The zenith position is shown when the moon line reaches the south (12 hour) mark at the top of the dial.

Since the moon travel is 50 minutes a day slower than sun travel, it takes 6 hours and 12 minutes of sun time for the moon to move 900. The light blue hour markings inside the horizon curve are the hours in sun time against which the moon line can be read. These hour readings tell the time either before or after the hour at which the moon reaches its zenith. This information is shown for only the 6 hours before and after zenith position. Readings, when the moon is below the horizon, are too complicated to display.


In somewhat similar fashion, the zenith position of a particular star, read against the South point at the top of the dial, is of major interest, and the approximate time of star rise and star set can be read when the star itself comes into or goes out of -.he horizon curve.


The time of high tide is roughly related to the time of the zenith position of the moon. The vagaries of the behaviors of the tide require that for any particular geographical position, the average difference in time between the zenith passage of the moon and the local high tide be shown as the difference between the moon line and the light blue tide line. This difference is considered constant for the particular place in question, and will be maintained because the moon and tide discs are driven at the same rate, both being slower than the sun rate. Bays, estuaries, shallows and obstructions delay, to a greater or lesser extent, the time that high tide occurs after the moon is directly overhead, So for your particular locality on the seashore. watch and establish the time interval between the moon's being overhead and the next high tide. This is called the establishment of the port for your location.

One of the light blue, opposed line scales of the tides is always intersecting the upper half of the horizon curve. In the vertical position, "H'' on the tide scale will coincide with the "HIGH" position at the top center of the curve at the instant of high tide. The time at which this occurs is in true Sur. time and is read between the sun line and the divisions of the gold 24-hour scale. Six hours and 12 minutes later, the tide scales will be horizontal, approximating low tides, one scale leaving the horizon curve and the other taking up intersection with it. The hours before the next high tide are now correctly shown as 6 hours and 12 minutes on the light blue figures.


The scale on the Tide Disc is marked in light blue and indicates approximately the stage or the height of the tide at any given instant. This is shown continuously, providing for
the two high and two low tides which usually occur each day. The non-uniform divisions on the tide scales are required because of the shape of blue ellipse of the horizon curve which, to avoid confusion, has been taken as the other coordinating curve. The individual markings on the Tide Disc are for 1/4, 1 / 2 and 3/ 4 to indicate the stage of the tide. The stage of the tide, as well as the hours before high or low tide can be read.


The conventional clock dial at the lower left displays the arbitrary time which is the same over approximately 1/24 of the earth's surface. If the time is standard time for that zone and not daylight saving time, then, for the positions precisely on the central meridian, as the 75th, 90th, etc., the standard time would correspond with the sun time of the other dials. For all other positions, and therefore for most positions in the United States, the zone time dials would be set arbitrarily and would be out of synchronism with the mean solar time, basis of astronomical displays. Changes made each year between standard and daylight saving time affect only the time shown on the ordinary clock dial, time on the other 2 dials remaining unchanged. Resetting twice a year to use daylight saving time is made by usual changing of ordinary time dial and then resetting all other dials to their previous positions, since they are on unchanging solar time.


This is time as referred to the precise 24-hour period which is the mean solar day period through the year. It is the basis for the time of all displays of natural phenomena and is used throughout the space dial and the world time dial.


The lower right dial with 24-hour division shows how the sequence of hours sweeps across any given position on the earth's surface. At any instant, therefore, this moving dial shows the solar time at any and all positions on the earth's surface on a 24-hour basis.

The hours representing daylight 6 (6 a.m.) through 12 (high noon surrounded by the sun) to 18 (6 p.m.) appear in dark blue on a bright gold background.

The hours of darkness 18 (6 p.m.) through 24 (midnight) to 6 (6 a.m.) are shown in gold on a dark blue background. This, of course, is solar time and must be corrected for the artificial time zoning which applies in the various world areas. See pages 26 through 29 for an explanation of this.


The sun is shown at its zenith position of high noon (the hour of 12) on both the World Time Dial and the Horizon and Hour Disc.

On the World Time Dial we see the figure 12 surrounded by an image of the sun. This represents 12 noon with the sun at its zenith. Draw an imaginary line from the figure 12 to the 'North Pole. As this imaginary line travels around the world it indicates that the time of high noon has arrived at the places directly below it.

As the World Time Dial rotates in a clockwise direction it changes the hour reading for the Greenwich longitude line on the map. This will be Greenwich mean time (G. M. T.) or Universal Time. Greenwich, England is located on longitude 00. When people-in other countries want to speak in a universal language about a particular instant of time, by common agreement, they refer to the instant time at Greenwich.

For example, it could be high noon or 12 hours at Sydney, Australia, but a person talking with someone in South America would say it is 2 hours Greenwich meantime.


For any city anywhere, the instant sun time is indicated on the World Time Dial by an imaginary radial line through the city to the hour scale.

For all named cities shown, zone corrections have been made and these show standard time readings at the outer end of the lead line. All locations require further corrections, such as for daylight saving and local variations.


If you like to cast your horoscope, which depends on the position of the sun and moon in the constellations of the stars, the Space Clock will be found helpful. It should be pointed out, however, that information read from the Space Dial represents the current picture of the heavens rather than that expressed by the signs of the zodiac.

The latter, some 2, 000 years ago, coincided with the constellations from which the signs took their names. The retrograde motion of the equinoxes along the ecliptic, during the course of 2,000 years has moved each backward into the constellation west of it, some 300

Therefore, the signs of the zodiac are not now associated with the same days of the year as they were 2,000 years ago.

More pictures of Spilhaus Space Clock and how to repair it.