Science Education and Outreach: Forging a Path to the Future ASP Conference Series, Vol. 431 Jonathan Barnes, Denise A. Smith, Michael G. Gibbs, and James G. Manning, eds. !c 2010 Astronomical Society of the Pacific

The Sunrise, Sunset, and Noontime Phenomena in Different Locations along the Same Longitude

Dr. Taha Massalha The Academic Arab College for Education, Haifa, Israel, [email protected]

1. Introduction

Throughout this past decade, we have studied the sunrise and sunset times in the Holy Land and their integration in school programs (Massalha & Abadi, 2006; Massalha & Timor, 2004). Specifically, we have evaluated the importance of recognizing such daily natural phenomena as related to sunrise and sunset times, understanding them better and invok- ing curiosity and thinking processes in students (Massalha & Abadi, 2008). We have also shown how important these time measurements are to local inhabitants in their planning of annual events (festivities and holidays) and daily prayer times. The research population included students of various sectors in Israel—Christian, Jewish, Moslem and Druze, since all share the concern of setting daily prayer times and year round holidays (Aveni, 1993; Richards, 1999). In the ASP convention of Septem- ber 2007, I presented a segment of my study along with some of the measurements completed by that date and the results obtained (Massalha, 2008). At the pace of the Astronomy Year, this paper will present the findings of a follow up study conducted over the past year jointly with physics students in Israel, Saudi Arabia and Turkey, and discuss in greater detail the concept of time, differentiating between Civil Time and Solar Time (DeVorkin, 1986).

2. The Concepts of Time Measurements

Time is a physical dimension, measurable by a number of methods subject to the phys- ical concept applied. These include:

1. The mechanical clock (spring, sand, water or candlelight operated), where the stored mechanical energy is released by constant doses and at regular intervals which compose the time unit; 2. The digital (electric) clock, where electrical energy replaces the spring energy and is also released by preset doses and at regular intervals to advance the digits; 3. The solar clock, where time is measured by the Earth position relatively to the sun. This measurement relies on the daily manifestation of a natural phenomenon and follows the Earth rotation about own axis. The time unit measured is a 24 hour interval, which is the time elapsing from the moment when the sun is first observed in a specific location and the moment when it is again observed in the 490 Sunrise, Sunset, and Noontime Phenomena 491

same location. To measure time by the solar clock, we rely on the changes to the shadow size and bearings. The solar clock by which the solar time is measured can be said to simulate the natural clock most closely (Massalha, 2008).

3. The Concept of Time

Our daily lives are managed by the civil time as measured by our wristwatches, clocks, and, more recently, cellular phone clocks. Civil time is that which serves us in our social and business pursuits, as opposed to the Solar time, which is measured relatively to a sun conjugated system. Solar time is measured with respect to the rotation of the Earth, relying on such celestial bodies which do not rotate with it. These can either be the sun or the stars, however they will provide different rates of rotation for the Earth—the sun will indicate the solar time while the stars will provide us with the sidereal time. The Earth rotation about own axis produces the day and night intervals across the planet, while the deflection of its rotational axis determines where the sun will rise and where it will set at a given moment. Thus, at midday (noontime) in the Holy City of Jerusalem, it will be early morning in New York and evening in Singapore. Simple calculation shows that every 15 longitudes introduce a one hour difference in the wristwatch measured civil time (4 minutes per longitude), hence this civil time has been commonly established as identical for all populations inhabiting the same area which spans across 15 longitudes (not considering the artificial change from winter to summer clock and vice versa, which change is introduced for purely financial reasons), with the solar time remaining constant along each longitude.

4. The Research Question

The central question in our study is whether the sunrise, noon and sunset times mea- sured along the same longitude are identical or different.

5. Research Proceedings

Participants in the reported study were physics students from the Israel Academic Arab College for Education, from Makka in Saudi Arabia and from Ankara in Turkey. Com- munication among the participants was managed through the email. Under the research program and for one full year, we measured the times when the following phenomena occurred in three cities located in three different countries: Jerusalem in Israel, Ankara in Turkey and Makka in Saudi Arabia:

1. Sunrise

2. Noontime

3. Sunset

The three cities studied are located on different latitudes, spanning between 21N (Makka, Saudi Arabia) and 40N (Ankara, Turkey), whereas their longitudes are closely 492 Massalha spaced (closer than an interval of 7 longitudes)—see Table 1. All three cities share the same local (civil) clock, yet they still differ in their sunrise, noon and sunset times, which difference varies from one time of the year to another. However, these measurements are important not only to the populations of these different areas but also to the scientific, social and educational thought sharing among students from three Mideastern countries, with the added value of increasing the cu- riosity of both students and teachers with respect to exploring the nature, extent and reasons for such difference.

Table 1. Longitudes and Latitudes in the Three Research Cities City Latitude Difference Longitude Difference Difference in Latitude in Longitude in Solar Time Makka 21◦25’ N 0 39◦49’ E 0 0 Jerusalem 32◦42’ N 11◦17’ 35◦18’ E 4◦31’ 18 Minutes Ankara 39◦56’ N 18◦31’ 32◦52’ E 6◦57’ 28 Minutes

6. Measurement Results

6.1. Sunrise Times As shown in Figure 1, there are practically no differences in the sunrise times among the three cities in the winter, whereas there is a significant difference in the summer. In Ankara, the sun rises earlier than in Jerusalem (with the latitudes of these two cities differing by 7 14’), and, in both of these cities, it rises much earlier than in Makka (which lies farther by 18 31’ by latitude from Ankara). This is not unexpected since, in the summer months, the sun is observed above the Cancer line (Tropic Cancer 23 27’ N). By solar time as shown in Figure 2, the differences in sunrise times among the three cities are smaller. By solar time, the sun rises later in Ankara than in Jerusalem or Makka in the winter, and earlier in the summer.

6.2. Noontimes Figure 3 shows significant differences in the noontimes measured in the three cities by the civil time clock (at noontime, the shadow is the shortest). All year round in Makka, noontime occurs later (by nearly 28 minutes) than in Ankara, where noontime occurs slightly later than in Jerusalem (by a difference of nearly 15 minutes). By solar time as shown in Figure 4, the differences in noontimes among the three cities are smaller. By solar time, all year round, noontime in Makka occurs merely 5 minutes or so later than in Ankara, where noontime occurs much later than in Jerusalem (by a difference of some 16 minutes).

6.3. Sunset Times As shown in Figure 5, there are relatively small differences in the sunset (civil) times among the three cities in the summer months (8 minutes max), which differences in- crease as winter sets in. In winter, sunset in Ankara precedes that in Jerusalem, and, Sunrise, Sunset, and Noontime Phenomena 493

Figure 1. Sunrise (Civil) Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset ofthecivilyearandending December 31st).

Figure 2. Noon (Solar) Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset ofthecivilyearandending December 31st). in both cities, the sun sets much earlier than in Makka (by a difference of 58 minutes). This is not unexpected since, in the winter months, the sun is observed above the Cancer line (Tropic Capricorn 23 27’ S). 494 Massalha

Figure 3. Noon (Civil) Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset ofthecivilyearandending December 31st).

By solar time as shown in Figure 6, the differences in sunset times among the three cities are significantly smaller both in the summer and in the winter months.

6.4. Discussion Our findings show that the three cities—Makka in Saudi Arabia, Jerusalem in Israel and Ankara in Turkey, located along close longitudes however on distant latitudes, differ in their sunrise, noon and sunset times, which difference is most apparent when civil time is used and less so in solar time (which follows the natural clock more closely). Both the civil and the solar time clocks show a large difference in the noontimes measured. Measurement of the daylight times in the three cities during the year of 2008 (Figure 7) has shown an asymmetry between the sunrise and sunset times, which finding requires additional measurements to evaluate for repeatability. Such asymmetry was also obtained in the first phase of our study (Massalha, 2008). As shown, Ankara receives a longer daylight time as compared with Jerusalem and Makka. Sunrise, Sunset, and Noontime Phenomena 495

Figure 4. Noon (Solar) Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset ofthecivilyearandending December 31st). 496 Massalha

Figure 5. Sunset Civil Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset ofthecivilyearandending December 31st). Sunrise, Sunset, and Noontime Phenomena 497

Figure 6. Sunset Solar Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset ofthecivilyearandending December 31st). 498 Massalha

Figure 7. Daylight Times in Jerusalem, Ankara and Makka throughout 2008 with the time axis given in arbitrary units (starting onset of the civil year and ending December 31st). Sunrise, Sunset, and Noontime Phenomena 499

7. Conclusion

In the reported study, we have shown that nature has a clock which is different from the artificial one we are using. The natural clock is fully harmonious with the Earth rotation about own axis and about the sun. Yet, it would have been impossible to run measurements like the ones described herein except with intelligent use of the artificial clock and the advanced means of communication currently available. We have also demonstrated productive scientific cooperation, on the internet, by students from three Mideastern countries sharing scientific, educational and cultural thoughts. No such research could have been attempted were it not for the advanced time measurement and information transfer technologies which enables the sharing of sunrise, noon and sunset times data.

References

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