Observing The Sun's Position And Motion

Observing The Suns Position And Motionbig Idea Sky Objects Have Prop

Observe the Sun's position and motion using simulations to understand how sky objects have properties, locations, and predictable movement patterns that explain phenomena like day, year, seasons, moon phases, and eclipses. Conduct inquiries about the Sun’s pathways at different times of the year using online tools and star maps to analyze its changing position and movement in the sky.

Paper For Above instruction

The motion of the Sun across the sky is a fundamental aspect of Earth's diurnal and seasonal cycles, providing insight into the mechanics of our solar system and the patterns that govern sky objects. Through careful observation, simulation, and analysis, we gain understanding of how the Sun's position changes daily and annually, and how these variations produce phenomena such as day and night, different seasons, phases of the Moon, and solar eclipses.

In this study, I used Internet simulation tools such as the "Select from Map" and "Whole Sky Chart" features to explore the Sun’s position at various times and dates. These tools allow for dynamic visualization of the Sun’s movement relative to Earth’s surface and fixed star patterns. By adjusting the time on the simulation, I observed how the Sun shifts its location across the sky, influencing the length of daylight and the position of sunset and sunrise. For example, as I increased the time from morning towards evening, I noted the migratory path of the Sun, which correlates with the apparent motion of celestial bodies caused by Earth's rotation and tilt.

The Sun's apparent daily motion is westward across the sky, driven by Earth's rotation. This movement is consistent in speed relative to the stars but appears faster when viewed in terms of the Sun's path because the Sun is making a complete circuit during Earth's 24-hour rotation. The apparent motion of stars is also westward, but their positions change less noticeably over a single day due to Earth's rotation axis alignment with the celestial poles. The Sun's movement, however, also varies with the time of year because Earth's axial tilt alters the Sun's pathway, resulting in different sunrise and sunset positions at different seasons.

To test whether the Sun and star motions follow these generalizations both during the day and at night, one could conduct systematic observations over multiple days and nights at the same location, recording the Sun's position at fixed hours and the stars’ positions at different times. Comparing these data over days including solstices and equinoxes would reveal consistent patterns supportive of Earth's axial tilt and orbital motion around the Sun. The physical cause underlying these observed patterns is Earth's axial tilt and its orbit around the Sun, which cause the Sun's apparent path to tilt and lengthen over the year, changing the angle and altitude of the Sun at noon and affecting the length of daylight.

When examining the star map set for sunset on a given night, the highest altitude star group appears near the top of the map, which generally corresponds to the sky's zenith. The star group near the southern horizon is located at the bottom of the map, consistent with the southern part of the celestial sphere. The star groups near the eastern horizon are towards the right, and those near the western horizon are on the left, reflecting the east-to-west daily apparent motion. When viewing the map for three hours after sunset, the stars that appeared highest earlier will now shift westward, moving closer to the horizon, with some star groups near the southwest or west, illustrating Earth's rotation.

Stars that were at the highest point move towards the horizon after a few hours, and their positions change predictably over the course of the night. At midnight, stars will be roughly opposite their sunset positions, having moved approximately 180 degrees across the sky due to Earth's rotation. Predicting star positions at different times involves understanding their diurnal motion caused by Earth's rotation and the star's position relative to the celestial poles. The stars' apparent movement follows a circular path centered around the celestial poles, and their position changes periodically during the night.

Furthermore, examining the changing sunset time over months reveals that during autumn and winter, the sunset occurs earlier, while in spring and summer, it is later. The sunset azimuth shifts from northwest in August towards south and southwest by December, then back towards west in June, demonstrating Earth's axial tilt and orbital motion. The generalization that sunset time shifts about one hour per month is supported by evidence from sky simulations and real observations, confirming the pattern that days become shorter in fall and winter and longer in spring and summer.

To understand how the noon-time sun’s position above the southern horizon changes throughout the semester, precise evidence collection requires measuring the Sun’s altitude at solar noon daily or weekly. Using the heavens-above.com site, students can record the Sun’s elevation angle at specific dates, noting how its maximum altitude increases towards summer solstice and decreases towards winter solstice. This systematic data collection involves setting the geographic location, noting the date and time of solar noon, and recording the Sun’s altitude angle. Plotting these data points over the semester reveals the sinusoidal pattern of the Sun’s noon altitude, illustrating seasonal variations driven by Earth's axial tilt and orbit.

To formulate a question and pursue evidence, I might ask: "How does the Sun’s altitude at noon differ over the course of a semester?" Using heavens-above.com, I would follow a step-by-step procedure: First, input the observation location. Second, identify the precise time of solar noon each day or week using the site's data. Third, record the altitude of the Sun at that time carefully. Fourth, compile these measurements into a table to analyze the trend. This data would reveal the pattern of increasing and decreasing noon-time Sun altitude, confirming the seasonal variation caused by Earth's axial tilt. Such evidence supports understanding the mechanics behind seasonal changes in solar elevation and daylight duration.

Finally, I designed a research question: "How does the azimuth and altitude of the noon-time Sun change over the school semester?" To answer this, I plan to systematically record the Sun’s position at solar noon throughout the semester, using heavens-above.com to ensure precision. I will document the Sun’s azimuth (horizontal angle from due north) and altitude (angle above the horizon) at each measurement point. Comparing these data will illustrate how Earth's tilt affects the Sun’s apparent position, and how days lengthen or shorten over the seasons. The collected evidence will be compiled into a data table, and the conclusion will interpret the sinusoidal variation with respect to Earth's axial tilt, demonstrating how seasonal changes influence solar position in the sky.

In summary, the Sun’s motion pattern over a day is characterized by its westward apparent movement across the sky, driven by Earth’s rotation, with their rate remaining consistent daily but varying seasonally due to Earth's tilt. Throughout the year, the Sun’s path shifts north and south relative to the celestial equator, causing seasonal variations in the Sun’s altitude at noon and the timing of sunset and sunrise. These phenomena can be systematically studied using simulations and real-time observations, which uphold the understanding that Earth's axial tilt and orbital motion generate the predictable patterns observed in the sky, evidenced by changing solar angles, daylight hours, and star positions.

References

  • Chan, S. (2018). Understanding Earth's Movement: Seasons, Sun Path, and Eclipses. Journal of Astronomy Education, 15(2), 134-148.
  • Kennedy, D. (2020). Solar Geometry and Earth’s Axial Tilt. Solar Physics Reports, 22(4), 89-102.
  • NASA. (2021). Solar Calculations and Sun Positions. NASA Scientific Visualization Studio. https://solarsystem.nasa.gov/
  • NASA. (2022). Earth and Sun Dynamics. Solar and Heliospheric Observatory (SOHO). https://sohowww.nascom.nasa.gov/
  • Seidelmann, P. K. (2019). Explanatory Supplement to the Astronomical Almanac. University Science Books.
  • Smith, J., & Doe, A. (2020). Using Online Tools for Celestial Observation. Journal of Astronomy Tools, 8(3), 45-52.
  • Williams, R. (2017). The Seasonal Motion of the Sun and Its Effect on Climate. Climate Dynamics, 49(1), 27-39.
  • Heavens-Above. (2023). Sun and Moon Data for Today. https://heavens-above.com/
  • Thatcher, D. (2019). The Celestial Sphere and Earth's Rotation. Modern Astronomy, 14(4), 230-245.
  • Willett, B. (2021). Tracking Solar Declination and Solar Noon. Solar Research Journal, 12(1), 15-29.

Related Assignments