ASTRONOMY EXERCISES

THE PHYSICS SUPERMARKET
  1. Introduction to Skyglobe
  2. Stars and Constellations
  3. A Day In
  4. Looking at the Stars
  5. Motion of the Stars 1
  6. Right Ascension & Declination
  7. Motion of the Stars 2
  8. Sidereal Time
  1. Motion of the Sun
  2. Motion of the Planets
  3. Astrology
  4. Time
  5. Navigation
  6. Motion of the Moon
  7. Solar Eclipses
  8. Distance of the Moon

1. Introduction to Skyglobe

In this exercise students learn to operate the Skyglobe program. The concept of the Celestial Sphere is introduced. Students set up the configuration file called hometown.cfg which automatically sets Skyglobe to display the sky above their location.  Top

2. Stars and Constellations

In this exercise students learn the names of several stars and constellations. Students learn that stars are moving rapidly through space but form fixed patterns because of their vast distance from Earth. Students investigate how the precession or the Earth's axis (its wobbling like a spinning top does near the end of its rotations) affects the location of stars in the sky.  Top

         

3. A Day In

Students visit several cities in key positions (e.g. Calcutta on the Tropic of Cancer) and spend a day watching the sun move across the sky on the key dates of the year - Solstices and Equinoxes. They then have to use their observations and imaginations to draw the apparent path of the sun across the sky as seen from outside it looking in.  Top

         

4. Looking at the Stars

Students investigate how the postion they view from, the time of the night and the day of the year affects what stars are visible in the sky. It is related to the angle of the horizon relative to the Earth's axis, the rotation of the Earth on its axis and the movement of the Earth around the sun.  Top

         

5. Motion of the Stars 1

In this exercise, students investigate the rotation of the stars about the North and South Celestial Poles during the night. They visit several cities and discover the angle of the Celestial Sphere's axis to the horizon is the same as the latitude of the city. This is confirmed from analysis of the geometry of the situation. Students use the knowledge and skills gained to determine a constellation's position in the sky a few hours before and after its present position.  Top

         

6. Right Ascension and Declination

Right Ascension and Declination have been mentioned in the previous exercises. In this one, students study this co-ordinate system in detail. Students are guided through this exercises by a series of diagrams that take them from the definitions to how the gridlines look relative to the horizon from outside the Celestial Sphere looking in and from inside the Celestial Sphere looking out.  Top

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7. Motion of the Stars 2

In this exercise, students investigate the effect on the night sky of the Earth's movement around the sun. They learn to predict the position of a constellation if they look at the same time of the night but say in 2 months time. Students investigate how the ranges of Declinations of stars always visible, stars sometimes visible and stars never visible, are related to the latitude of the location.  Top

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8. Sidereal Time

Students are introduced to the concept of a clock which keeps time relative to the stars. Sidereal Time is defined and students learn to calculate the Sidereal Time for a given Solar Time. They then learn to predict which stars are on the Meridian at any time of the day or night on any day of the year.  Top

         

9. Motion of the Sun

Students investigate the drift of the Sun across the background of stars. The easterly drift is related to the movement of the Earth around the Sun and the drift away and towards the horizon is related to the angle of the Earth's axis relative to the plane of orbit around the Sun. The concept of the ecliptic is introduced. Students learn to predict the angle of the Sun above the horizon at noon on any day of the year at any location given its latitude.  Top

         

10. Motion of the Planets

In this exercise, students follow the progress of the planets as they orbit the sun. By changing Skyglobe to Sidereal Time mode, time can be advanced in 1 sidereal day steps meaning the stars seem to remain fixed and the sun and the planets drift along the ecliptic. Retrograde motion is observed during the drift. After setting the present time and recording the Right Ascension of each planet, the students position the planets in their orbits as they are on that day. Students then determine the periods of the planets.  Top

         

11. Astrology

Students follow the drift of the sun along the ecliptic as it passes through the signs of the zodiac. They travel back to Athens in the year 570 BC and record the dates that the Sun was in each Star Sign in ancient times. They discover why the Tropics of Cancer and Capricorn were given their names. Comparing the present day times that the Sun is in each Star Sign shows the two to be about a month different - due to the precession of the Earth's axis. I wonder if Zelda the Mystic allows for this when making predictions!  Top

         

12. Time

In this exercise students investigate the time difference between different locations on the Earth. They also discover that the time on their watch is not the same every day when it is noon - the sun is on the meridian. This is related to the changing speed of the Earth in its orbit around the Sun. The explanation of why the tilt of the Earth's axis also has an effect, is beyond this study.  Top

         

13. Navigation

In this exercise students use what they have learned in the Motion of the Sun and the Time exercises to determine the latitude and longitude of a ship using the angle of the sun at noon and the time on the ships chronometer set on Greenwich time.  Top

         

14. Motion of the Moon

Students determine the Right Ascension of the Moon every three days for about 5 weeks. Its position relative to the Earth is determined revealing the complex path followed by the Moon as it orbits the Earth. Students then determine the Sidereal and Syndodic periods of the Moon. Finally, the phases of the Moon are studied.  Top

         

15. Solar Eclipses

Students investigate past and future eclipses of the sun.  Top

         

16. Distance of the Moon

Students follow the lead given by John as he goes about measuring the distance of the Moon from the Earth. He chooses his time of viewing and location wisely so that the distance can be determined from the angle of elevation of the moon at that time.  Top