The Sun Elevation, Daylight Hours and Seasons

The height of the sun is closely linked to the seasons. Different seasons lead to different sunrise and sunset hours. The sun's setting and rising periods differ depending on the month, as seen by the observation. The observation was carried out by meticulously recording the various intervals, as well as the minutes it took for the sun to set and rise. This data was gathered over the course of five weeks.

The data are gathered in order to assess the effects of various seasons on the sun's location. Every time, an object 24 inches in length was used to make the observation at 12:00 PM. The On January 26th, the sun rose at 7:18AM, and set at 5:26PM. At the time of observation, the object cast a shadow 40 inches in length (Paul, 2016). On 30th January, the sun set a shadow 32 inches long, having risen at 7:15, and setting at 5:30Pm. On the third day, February 20th, the object set a shadow 30 inches long. This day, the sun arose at 6:53, and set at 5:53Pm. On March 15th, the sun rose at 7:21AM, and set at 7:16Pm (Paul, 2016). The sun cast a shadow 23 inches long. 4th April was the last day. On this day, the sun rose at 6:51AM, and set at 7:34. The sun set a shadow only 17 meters long.

The variation between the shadow heights and dates is closely related to the times the sun rose and set. The shadow length is an indication of the varying sun elevation and positioning at different times. This is unlike the distance between the earth and the sun, which does not change. Rather, the observations suggest that it is the angle of the sun’s rays to the earth that changes through the year.

The observations show that there is a close relationship between the sun’s elevation, and sunrise and sunset. According to data collected, the longer the day, the shorter the shadow. This will be illustrated in the observation data and graphs below, whereby the object varies from a high of 40 inches in January to a low of 17 inches at the same time in April (Ray, 2008). This means that among other things, the sun’s rays are changing in angle, as the sun moves away from the tropic of Capricorn to the equator, and onwards to the tropic of cancer, in time for summer.

Observations

(Warren, 2013)

The data above is a representation of the different shadows set by the object, as well as the different times that the sun rose and set.

From the data, the day starts earlier as the year progresses. Since the observation was made in the northern hemisphere, it can also be deduced that the closer to summer the days get, the longer the days become (Keith, 2009). Form the observation above also, it is clear that as the days get longer, and the year progresses in the meantime, the angle of sun’s rays to the earth’s surface increasingly becomes more acute, such that by June, the sun is practically overhead, and can therefore the object cannot set a shadow over the earth.

(Ellis & David, 2017)

The diagram above represents the daylight start dates.

The readings above are a representation of the observations discussed before. They show a clear tendency, where the day starts earlier as the year progresses.

(Ellis & David, 2017)

This is a representation of the sun’s elevation in degrees, in relation to the different time periods (different sun rising and setting times). As the year progresses and the days become longer, the angle to the earth becomes smaller. This angle is expected to become smaller as the year progresses, as is discussed severally in the paper. Taking the shadow to be one of the sides of a right – angled triangle, and the object the other side, it is clear that the shadow will become shorter, meaning that the path of the sun’s rays (the hypotenuse will become steeper, and therefore result in a smaller acute angle (Ray, 2008).

a

b

This is the representation in January (approximate), whereby the object is denoted as a, and the shadow as b.

a

b

In April, b is smaller, meaning that the angle becomes less.

Analysis

The sun always makes a big ecliptic circle around the earth. While this circle is imaginary and the earth in fact moves around the sun, this circle is represented in the different elevation angles that cast shadows of different heights, at the same time of the day. It the same time, this is representative of the different times of the day that the sun rises and sets (Paul, 2016).

The angles that denote the sun’s elevation differ as the year progresses. This is in connection to the revolution that the earth takes as it goes around the sun on its annual journey. The sun, while never being far away from the sun, is nonetheless closer to the earth in January, and farthest in June. However, the angle of elevation means that the sun’s rays are applied to the earth at different angles. This not only causes variations in temperature, but also results in differences in day length (Warren, 2013). Depending on the time of the year, the sun will rise at different times, and set at different times due to the spherical angles and triangles that help describe the earth.

The readings discussed above were done in the northern hemisphere. This by itself accounts for some of the results obtained, and specifically, the size of the shadow. As the year progresses, the sun will continually get higher and higher form the surface. This means that at the same time, the shadow will be at different places.

The day times change, but at the same time the days become smaller and smaller as time gets away from the winter. Therefore, while the day is around ten hours long in January, it is more than 13 hours in April. This day reaches its peak in summer. In the North Pole around this time, people can enjoy 24 hours of sunshine during the summer solstice (Warren, 2013). At this time, the sun passes directly above the tropic of cancer. In winter, the sun is in the far extreme, passing directly overhead the tropic of Capricorn during the winter solstice.

As the sun goes through the motions and the days become longer, the temperatures become warmer and the shadow, shorter. In some ways, this means that the angle at which the sun’s rays reach the earth are becoming more acute. Since the sun’s distance from the earth never changes, but the temperatures do change it means that, the ray’s angles in relation to the earth are the cause of the differing temperatures (Keith, 2009). From this deduction, it can be concluded that the steeper the angle, the shorter the shadow, and the longer the day.

Reflection

One of the important things apparent form the reading above is the relationship between the length of the shadow (the angle), and the position of the sun in relation to the earth. The sun’s revolutions are not perfect. Therefore, the sun will in a way wobble in its orbit as it goes around the sun. This results first in the ecliptic circle, which the sun and the stars follow as seen from the earth. In this respect, the sun’s distance does not change, but the earth’s positioning in this relation does change (Ray, 2008). The second observation is that the angle of the sun’s rays in relation to the earth is the reason for the difference in temperatures, rather than the constant distance.

From the observation, I was also able to understand that the difference between the different lengths of the day is a direct consequence of the sun’s movement between the tropics of cancer and Capricorn. At the time the readings were done, it was in winter, transitioning to spring. During this time, the days were short, but were gradually becoming longer. This meant that the sun was coming closer to the northern hemisphere, and thereby shortening the angle with which its rays reach the earth.

References

Ellis, M., & David, T.(2017). Sunrise, Sunset: Using Personal Observations to Understand Changing Sun Patterns from an Earth Perspective. Science Scope, vol. 40(7), 4-98.

Keith, T. (2009). Solar Motion From Australia. Teaching Science, vol. 55(4), 9-75.

Paul, H. (2016). When Our Round Earth Was First Measured. The Science Teacher, vol. 83(6), 12-67.

Ray, F. (2008). The Sky. Teaching Science, vol. 54(3), 8-123.

Warren, B. (2013). Time Zones and Daylight Saving. Australian Mathematics Teacher, vol. 69, (2), 7-54.