[Home]>[Miscellaneous]>[8. Astronomy]>[2. Astronomical subjects]>[2.9 The zone times]

Previous webpage:           2.8 Range of the sun measured along the sky
To the end of this webpage: End
Next webpage:               2.10 The tropics

# 2.9 The zone times

Frank L. Preuss

It is here about the conversion from the degree of longitude of a place to the time of that place, therefore about the way, to calculate time according to degrees to the way to calculate time according to hours.

As an example we take here a few places in Germany. Germany belongs to the time zone +1 and it is called the Central European Time Zone. It is based on the 15th degree of eastern longitude and that means that the time of the 15th degree of eastern longitude agrees with the true sun time, therefore, when the sun really stands there at its highest point at 12 o’clock, has reached its culmination point.

The places of the time zone, which are not situated on this basic degree of longitude, have the same clock time to make life easier. Formerly every area had its own time, therefore a time, which agreed well with true sun time, but with modern means of traffic and communication that would be too complicated today. Therefore the matter was simplified and uniform times were fixed for certain areas.

The conversion of angle time to hour time is based on the earth rotating by an angle of 1 degree in 4 minutes; that are 0,06667 hours.

Now follows a table, which shows the degrees of longitude of a couple of places and also their midday time:

 1 2 3 4 5 6 7 Place Time measured in angles Time measured in hours Degrees of longitude Midday time Degrees and minutes Degree Deviation from 15.00 degrees Deviation from 15.00 degrees Clock time Clock time Degrees Hours Lyck 22o22" 22.37 -7.37 -0.49111 11.50889 11:31 Memel 21o10" 21.17 -6.17 -0.41111 11.58889 11:35 Königsberg 20o32" 20.53 -5.53 -0.36889 11.63111 11:38 Elbing 19o25" 19.42 -4.42 -0.29444 11.70556 11:42 Danzig 18o40" 18.67 -3.67 -0.24444 11.75556 11:45 Breslau 17o04" 17.07 -2.07 -0.13778 11.86222 11:52 Wien 16o24" 16.40 -1.40 -0.09333 11.90667 11:54 Görlitz 15o00" 15.00 0.00 0.00000 12.00000 12:00 Stettin 14o31" 14.52 0.48 0.03222 12.03222 12:02 Berlin 13o24" 13.40 1.60 0.10667 12.10667 12:06 Leipzig 12o25" 12.42 2.58 0.17222 12.17222 12:10 München 11o34" 11.57 3.43 0.22889 12.22889 12:14 Hamburg 10o00" 10.00 5.00 0.33333 12.33333 12:20 Stuttgart 09o11" 9.18 5.82 0.38778 12.38778 12:23 Frankfurt 08o41" 8.68 6.32 0.42111 12.42111 12:25 Bern 07o26" 7.43 7.57 0.50444 12.50444 12:30 Köln 06o57" 6.95 8.05 0.53667 12.53667 12:32 Aachen 06o05" 6.08 8.92 0.59444 12.59444 12:36

With the place marked yellow the true midday time agrees with the average midday time. And that is, because that place is situated on that meridian, which determines this time zone, the Central European Time Zone, +1. On all the other places an average midday time was forced upon as midday time to fit them to that time system.

But the matter was not just simplified and standardized times fixed for certain areas, also other differences were straightened out, which resulted from other reasons. And the whole so that everywhere on earth a standardized time and clock system exists.

Only with the introduction of railway lines did the necessity of a unified time system arise, so that the personal and the passengers did not have to convert the clock time all the time and a timetable could be fashioned simply.

Formerly with the mail coach the passenger had perhaps a pocket sun dial with him. And at the time of the mechanical clock he had perhaps checked the time on his pocket watch, now a mechanical pocket watch, with the time of the church steeple, also a mechanical clock. But both times were probably not too different, compared to today, where the midday time can quite considerably deviate from the midday time of 12 o’clock and take from men the feeling of the time of the day. And when then still a summer time is introduced, it becomes even still worse with the confusion. And that then leads to men just only looking at the watch, or today at the smartphone, and no more turn the look upwards. And that then also contributes to also no longer turning the look upwards spiritually.

That is the beauty, when one deals with astronomical questions and answers; one deals with creation; and with it with the creator. The look upwards is again practised.

"I try to avoid looking forward or backward, and try to keep looking upward."

That is of course first of all a spiritual looking upwards, but a physical looking upwards is already a good start, because it also goes in direction of the creator and his work. To look at night at the world of the stars is an awe-inspiring matter. The same is to watch at daytime a sunrise or a sunset; there one looks directly at the sun. But otherwise one avoids looking at the sun, and when one now does measurements of the stand of the sun it is not advisable to take a sight on the sun, but it is more practically to observe its shadow and measure its angle to the shadow giving point and to also record the change of the position of the shadow with time.

When one now builds for himself a simple sun observatory from two pages of paper, one can with simple means and in quite a short time determine the position of the sun at midday and with it determine how far the calculated clock time agrees with reality, therefore determine at what clock time the sun really stands highest in the sky.

The above table covers almost exactly the whole Central European Time Zone, therefore 15 degrees. That is from 7o30' to 22o30'.

The West European Time Zone goes from 7o30' to -7o30' and its center is on the Prime Meridian.

The above table covers with this also a period of time of one hour and is therefore a good example of a use of a time zone; the center is in the middle of the time zone and the two edges are both about half an hour away from it.

I have once gone on a trip with a cart lasting several weeks. The longest distance was 45 km, which we have managed in one day. The normal travelling speed was less than 4 km/h. When now a stage coach is in a hurry and the horses are changed and perhaps also the coachman, it may manage perhaps 200 km in a day. The 50th parallel has a radius of cos50o x 6378 = 0,6428 x 6378 = 4100 km. The 50th parallel is then 2 x 4100 x 3,14 = 25 750 km long. For this distance the sun needs 24 hours. For 200 km it then needs 200 x 24 / 25 750 = 0,2 hours and that are 12 minutes. When the people in the stage coach travel in east west direction, their true time has changed by 12 minutes and there the travellers will probable hardly make the effort to reset their watches. They perhaps might have made that at the end of their journey, after they got acquainted with the local time.

So there was therefore little need for something like time zones and zone times.

The above table shows a time difference of 12 minutes between Hamburg and Köln and that would then also be the horizontal component of the distance between these two places, 200 km. And that would allow imagining what distance a mail coach in a hurry might have travelled in one day. The distance of 200 km would therefore be the distance of 3 degrees of longitude, from the 10th to the 7th degree of longitude.

This is the end of "2.9 The zone times"
To the German version of this chapter: 2.9 Die Zonenzeiten

Previous webpage:                 2.8 Range of the sun measured along the sky
To the beginning of this webpage: Beginning
Next webpage:                     2.10 The tropics

[Home]>[Miscellaneous]>[8. Astronomy]>[2. Astronomical subjects]>[2.9 The zone times]