# The Moon in plain sight: reading notes

Original short teaching notes and questions by CodexWork, checked against the three primary references below on 24 October 2026. These are paraphrases, not quotations or a NASA-authored lesson. No photographs or third-party illustrations are included.

## N1 · A lit sphere, a changing view

The Moon reflects sunlight. Normally, half its sphere is sunlit; from Earth we see different amounts of that half as the Moon travels around us. New Moon puts the mostly unlit face toward us. Full Moon puts the lit face toward us. Ordinary phases are a change of viewing geometry, not Earth’s shadow. A lunar eclipse is the separate exception.

Source: [moon-phases](https://science.nasa.gov/moon/moon-phases/)

## N2 · Names describe both shape and direction

Waxing means the visible lit fraction is increasing; waning means decreasing. First quarter is a half-lit disk heading toward full; last quarter is a half-lit disk heading toward new. “Quarter” names progress through the cycle, not the lit fraction. Gibbous means more than half the disk is lit. The cycle averages about 29.5 days. One half-lit view alone does not tell you whether it is waxing or waning.

Source: [faq](https://aa.usno.navy.mil/faq/moon_phases)

## N3 · Phase is necessary, alignment is another condition

A lunar eclipse needs full Moon and a path through Earth’s shadow. A solar eclipse needs new Moon and an alignment that places the Moon in front of the Sun for an observer. Neither happens every month: the Moon’s orbit is tilted relative to Earth’s orbit around the Sun, so it usually misses the required alignment.

Source: [eclipses](https://science.nasa.gov/moon/eclipses/)

## N4 · A dim outline inside a crescent

Sometimes the unlit-looking part of a crescent Moon is faintly visible. Sunlight reflected from Earth can illuminate that part of the Moon; this is called earthshine. A dim outline does not mean the Moon is generating its own light.

Source: [moon-phases](https://science.nasa.gov/moon/moon-phases/)

## A second visit

The expanded notebook adds N4 and its earthshine application question. It also develops the first-quarter explanation without changing its correct answer. The other five questions retain their content. Import this as updated material for the same notebook: your earlier answer should remain inspectable, the changed explanation should need review, and untouched questions should retain their states. This is an authored update, not a recorded learner outcome.