Eclipses: Practice Problem Solutions

1. Solar eclipse: new Moon. Lunar eclipse: full Moon.

2. The umbra is the dark central part of a shadow where the Sun is fully blocked (total eclipse). The penumbra is the lighter outer part where the Sun is only partly blocked (partial eclipse).

3. The Sun is about 400 times wider than the Moon but also about 400 times farther away, so they appear about the same size in the sky.

4. The Moon's orbit is tilted about 5 degrees to Earth's orbit, so most months the shadows miss. Eclipses need a new or full Moon near the nodes where the orbits cross.

5. Sunlight is bent and filtered through Earth's atmosphere, and the red light reaches the Moon, like all of Earth's sunrises and sunsets at once.

6. Safe: ISO 12312-2 eclipse glasses, a pinhole projector. Unsafe: looking at the Sun with the naked eye, or through a camera, binoculars or telescope without a proper solar filter.

7. An eclipse in which the Moon is too far from Earth to cover the Sun completely, leaving a bright ring of the Sun around the Moon.