Answer:

1. During which phase/s of the moon is it possible for an eclipse of the sun and an eclipse of the moon to occur?

— Solar eclipses happen only at the new moon phase, when the Moon is between Earth and the Sun. During a solar eclipse, the Moon casts a shadow on Earth, and blocks or partially blocks our view of the Sun.

2. Describe the effect that a small change in the distance between the earth and the moon has on the size of the shadow causing the eclipse.

— Size Increases With Distance, the reason why the penumbra is so much larger has to do with the distance of the Moon from Earth and the fact that the Moon is smaller than the Sun. With growing distance from the Moon, the diameter of its umbra decreases as the Moon appears to diminish in size.

3. As seen from earth, how does the moon's apparent size compare to the apparent size of the sun? How can an eclipse be used to confirm the answer to this question?

— Solar Eclipses. By an amazing coincidence, the moon's apparent size in our sky is almost exactly the same as the sun's: about half a degree. This means that it's possible, as the new moon passes by the sun in its monthly trip around the ecliptic, for the moon's disc to completely cover the sun.

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