Glossary

 Role play : Changes in the Time of Moonrise
Procedure:

1. Stand in pairs, at least a couple of feet apart.

2. In each pair, the student on the left will be the Earth and the student on the right will be the Moon.

3. Fix the direction from which the sunrays are coming.

4. Start with the Full Moon position. This means, the Sun and the Moon should be on  opposite sides of the Earth. Let the Moon face the Earth.

5. Let the Earth stand such that the Moon is on the left hand side and the Sun is on the right hand side. At this point the person on the nose (Nitu) can see the Moon on the eastern horizon and the Sun on the western horizon.

6. Now, the Earth should start rotating. At the same time, the Moon should also start revolving around the Earth very slowly. Make sure that the directions of rotation of the Earth and revolution of the Moon are same (use the Right Hand Thumb Rule to find the directions of rotation and revolution).

7. The Sun will set, and the full Moon will rise for Nitu (Figure 1).

8. Now by the time the Earth completes one rotation (faces exactly away from the Sun) the Moon has moved ahead by a step or two. So Nitu will not be able to see the Moon rising on the eastern horizon at the time of sunset. The Earth will have to rotate a little more for Nitu to see the Moon. That means the waning gibbous Moon rises between the time of sunset and midnight and sets between the time of sunrise and noon. Have you noticed the gibbous Moon in the sky during the day? If not, look for it!

9. If you fast forward a little, so that the Moon is at waning half position (the Sun-Earth-Moon angle is 90°) you will see that the waning half Moon rises at midnight and sets at noon (Figure 1).

10. Similarly, the waning crescent rises between midnight and sunrise and sets between noon and sunset.

11. Finally, at the New Moon position, the Sun and the Moon will rise together and set together. However, we do not notice the Moon because only the dark part of the Moon is visible from the Earth.

12. Now find out the rising and setting times of the waxing crescent, the waxing half Moon and the waxing gibbous.

Draw a diagram explaining the changes in the timing for the moonrise.

Use your notebook for drawing. Please write following on page where you are drawing- The Basic Astronomy Module: Unit 2: Lesson 4: Activity 1 & your Login ID

Let us find out how much later the Moon rises everyday.

You can find the timings of moonrise in local calendars or newspapers. Find out the time of moonrise for two consecutive days and check whether our prediction matches with them. If not, how much difference do you get?

At the time of the Full Moon, it rises around the time of sunset, and at the time of New Moon, it rises around the time of sunrise. That means in 15 days it lags by 12 hours ( i.e. 720 minutes). In one day it would lag by 720/15=48 minutes.
 

Figure 1: Changes in time of moonrise