GEO. 108 – Earth-Sun Geometry Extra Credit Exercise (15 points) Name:______________________
Go to this website: DUE BY FRIDAY February 6th, in class.
www.learner.org/jnorth/tm/mclass/eclipticsimulator.swf
If you cannot access it, contact me and I will help you! You also need to refer to your text, pages 49-54. On the website simulation, use the “click and drag” feature in three places to operate the simulation: click and drag the globe to change its position during its revolution, click and drag the arrow positioned over the months of the year, or click and drag the line of latitude to change the position of the stick figure on the globe.
The simulation uses the term “Sun’s altitude” to refer to the angle of incoming sunlight.
1. In our text, we learn that the term “______________________________________________________” refers to the circle that separates the day hemisphere from the night hemisphere, and the placement of that circle changes with the change of the seasons.
2. March 21st and September 21st are given the term “________________________________,” and these two dates mark two important seasonal changes, from Winter to Spring, and Summer to Fall, respectively.
3. December 21st and June 21st are given the term “___________________________________” and these two dates mark the remaining two seasonal changes, from Fall to Winter and Spring to Summer, respectively.
4. On the website simulator, place the Earth at the date of March 21st. Describe how the Earth is divided between illumination and darkness? In other words, what two points on the Earth does the dividing line pass through?
5. In our text, the term “______________________________________” refers to the spot on the Earth where the Sun is directly overhead at a particular moment. At this spot, with the sun directly overhead at a 90 degree altitude, and the Sun’s rays are striking the Earth at a 90 degree angle. This is the maximum solar energy.
6. On the website simulator, with the Earth still at March 21st, place the stick figure at 0 degrees latitude, or the
EQUATOR. Identify the altitude (angle) of the Sun here: ___________________ This should match Figure
1.22 in your text, and you see that on this date, the Equator is the _________________________ point.
7. On the website simulator, place the Earth at September 22nd, and place the stick figure at 39.0 degrees N latitude, which is our latitude. Identify the Sun’s angle or altitude at this latitude, on this date, and estimate the number of hours of sunlight at this latitude on this date.
8. On the website simulator, place the Earth at June 21st, and place the stick figure at 23.5 degrees N, or as close as you can get (I could get it at 23.4 degrees). What is the altitude of the Sun here? ___________ This is the __________________ point. This line of latitude is called _______________________________________.
9. With the Earth at June 21st, move the stick figure to a point between 66.6 degrees S and 90 degrees S. What are the conditions of illumination at this latitude on June 21st? Referring to Figure 1.23 in our text, how long will those conditions persist, during the 24-hr day at this latitude on June 21st?
10. On the website simulator, place the Earth at December 21st. Place the stick figure at 23.5 degrees S, or as close as you can get. What is the angle of the Sun’s rays at this point? This is the _______________ point, and the line of latitude is called ______________________________________.
11. With the Earth at December 21st, move the stick figure back to that point between 66.6 degrees S and 90 degrees south. What are the conditions of illumination now? How long will those conditions persist, during the 24-hr day at this latitude on Dec. 21st? (Hint: refer to Figure 1.23 in our text)
12. Place the Earth at February 1st. Place the stick figure at the following locations and identify the angle of the sun’s rays, or sun’s “altitude” at each of these locations.
37 degrees north latitude__________________________
23.5 degrees south latitude______________________
48 degrees south latitude ______________________
68 degrees north latitude _______________________
13. Using the website simulator, identify altitude of the sun on the day of your birth, at the place of your birth. To do this, you will also need to use the Internet to look up the Latitude of the town where you were born. This is simple: just Google “Town, State, Country Latitude” and you should find this. If you were born in a location too remote to be found, use the nearest town/city of significant size.
Town/State or Country: _______________________________ Date:_________________________________
Sun’s Altitude:__________________________________
14. On the day of your birth, what location on Earth was the subsolar point?
Date:_________________________________ Subsolar Point:_______________________________________