Q1.
As can be seen in Fig. 11.5a, on the New Moon day, the Moon appears closest to the Sun and it appears farthest on the Full Moon day. Is this not what we also observed in Activity 11.1?
Answer
Yes — it is the very same result, arrived at from two different directions.
- In Activity 11.1 you filled in a column called "Moon and Sun separation in the sky compared to the previous day". Through the waning fortnight you kept writing Closer, and at the same time the bright portion kept Decreasing; through the waxing fortnight both entries reversed.
- In Fig. 11.5a you can see why. At position E the Moon lies in the direction of the Sun, so from Earth the two appear together in the sky; at position A the Moon lies on the far side, so the two appear at opposite ends of the sky.
Why it happens: The observation and the diagram are two views of one geometry. The angle between the Moon and the Sun as seen from Earth is precisely what decides how much of the lit half is turned towards us. So the separation and the phase can never disagree — a full Moon must be far from the Sun in the sky, and a thin crescent must be near it.
Check it yourself: On a full Moon evening, look east as the Sun sets in the west. The Moon will be rising almost exactly opposite the setting Sun.