Multiple Choice (circle correct answer within brackets)

1. The gnomon (or style) of an equatorial sundial represents the Earth's [axis, Equator] of rotation.

2. The dial plate of an equatorial sundial represents the plane of the Earth's [axis, Equator].

3. The upper dial face of an equatorial sundial represents the [Northern Hemisphere, Southern Hemisphere].

4. The lower dial face of an equatorial sundial represents the [Northern Hemisphere, Southern Hemisphere].

5. The 12 o'clock hour line (also known as the meridian line) that divides the dial face in half represents your line of [latitude, longitude].

6. Relative to a horizontal surface, the gnomon of an equatorial sundial should be inclined at an angle equal to your [latitude, longitude].

7. Relative to a horizontal surface, the dial plate of an equatorial sundial should be inclined at an angle equal to the [complement, supplement] of your latitude.

8. [Complementary, Supplementary] angles are two angles for which the sum of their degree measurements equals 90 degrees.

9. Viewed from above the North Pole, the Earth appears to rotate [clockwise, counterclockwise]. Viewed from above the South Pole, the Earth appears to rotate [clockwise, counterclockwise]. Hint: If necessary, experiment with a virtual globe before answering these questions.

10. Sun shadows fall in the [same, opposite] direction as the Sun.

11. For equatorial sundials located in the Northern Hemisphere, morning times are located on the [left, right] side of the upper dial face (facing south).

12. During the day, the gnomon shadow appears to move [clockwise, counterclockwise] around the [upper, lower] dial face.

13. The Earth's [rotation, revolution] causes the gnomon shadow to appear to move around the dial face.

14. The Earth's [rotation, revolution] causes the gnomon shadow to move from the upper dial face to the lower dial face, and vice versa.

15. Daylight Saving Time is Standard Time (wristwatch time) plus one hour. When Daylight Saving Time (DST) is in effect, Solar Time (sundial time) is [earlier, later] than DST. Hint: Remember the mnemonic, "Spring forward; fall back."

Short Answer (write clear and concise answers)

1. When doesn't an equatorial sundial work?
   
   
   
2. Explain why the gnomon (or style) of a properly oriented equatorial sundial will not cast a shadow on the dial plate on the day of the equinoxes (MAR 20, SEP 22).
   
   
   
3. The Earth rotates once every 24 hours (approximately). How many degrees does the Earth turn in one hour? Hint: One complete rotation of the Earth is 360 degrees. Verify your answer by using a protractor to measure the angle formed by the sundial center and two adjacent hour lines on the dial face.
   
   
   
4. Why do time zones generally run north-south instead of east-west? Why are time zones nominally 15 degrees of longitude in width? Hint: There are 24 Time Zones around the world.
   
   
   
5. The Sun and Earth are parts of an interconnected system. Use the words "rotation" and "revolution" to summarize your short-term (day-long) and long-term (year-long) observations of the equatorial sundial.
   
   
   

For Further Thought

1. Are you clock-wise? Why is "clockwise" clockwise? Remember, mechanical clocks were invented in the Northern Hemisphere.
   
   
   
2. Why is it incorrect to say that 12 noon is 12 p.m.? Hint: The "m" in p.m. means "meridian" or "midday."
   
   
   
3. Longitude is equivalent to time (and vice versa). Explain. What would be the difference in longitude between two sundials separated by a 12-minute time difference? Hint: Reduce the rate of the Earth's rotation from degrees/hour to degrees/minute.
   
   
   
4. Would your sundial read the same time as another sundial 100 miles directly north of you? Would the gnomon shadows be the same length?
   
   
   
5. Does an equatorial sundial work the same north and south of the Equator? Would an equatorial sundial work at the North and South Poles?
   
   
   

Bonus Question

List three reasons that Solar Time (sundial time) may be different from Standard Time (wristwatch time). Hint: Refer to "Solar Time Versus Standard Time," SCSA Educator's Guide to Equatorial Sundials.