--- title: "Phases of the Moon" description: "Explain Moon phases as changing views of the Moon's sunlit half as it orbits Earth, and describe how solar and lunar eclipses occur" canonical: https://lightmysky.com/learn/science/phases-of-the-moon-mt_4V-vYhFUcm source: https://lightmysky.com/learn/science/phases-of-the-moon-mt_4V-vYhFUcm.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Phases of the Moon Explain Moon phases as changing views of the Moon's sunlit half as it orbits Earth, and describe how solar and lunar eclipses occur Subject: Science · Area: Space Systems & Earth's History · Ages 11 to 12 Page: https://lightmysky.com/learn/science/phases-of-the-moon-mt_4V-vYhFUcm ## Ready when they can - Explains that the phases of the Moon arise from the changing geometry of Sun, Earth, and Moon, not Earth's shadow - Describes the sequence of Moon phases over a cycle averaging about 29.5 days - Distinguishes between a solar eclipse (Moon between Sun and Earth) and a lunar eclipse (Earth between Sun and Moon) ## Lesson: The Moon's Changing Faces The Moon reflects sunlight; it does not make its own light. Except during a lunar eclipse, the Sun lights about half its surface. As the Moon orbits Earth, our view of that sunlit half changes. At new Moon, the sunlit half faces away from us. At full Moon, it faces us. The Moon stays the same shape. Ordinary phases come from this changing view, not Earth's shadow. *(drawing: The cycle averages about 29.5 days. After waning crescent, the sequence returns to new Moon. The cells show order, not equal time intervals.)* Waxing means the sunlit part visible from Earth is increasing; waning means it is decreasing. A crescent has less than half its disk lit; gibbous has more than half. At either quarter phase, half the visible disk is lit. A full phase cycle averages about 29.5 days. Starting at full Moon, last quarter is about 7 days later, new Moon about 15, and first quarter about 22. These are approximate times. A solar eclipse happens at new Moon when the Moon passes directly between the Sun and Earth. Its shadow reaches part of Earth, where the Sun appears partly or fully covered. Most new Moons are not eclipses because the Moon's orbit is tilted and its shadow misses Earth. Never look directly at the Sun. For this lesson, use videos or models instead of direct Sun viewing. A lunar eclipse happens at full Moon when Earth lies directly between the Sun and Moon and Earth's shadow falls on the Moon. Most full Moons miss Earth's shadow because the Moon's orbit is tilted. During a total lunar eclipse, the Moon can look reddish because Earth's atmosphere bends some sunlight into the shadow. Unlike a solar eclipse, a lunar eclipse is safe to watch directly. **Recap.** Phases are changing views of the Moon's sunlit half and repeat about every 29.5 days. Eclipses need close alignment so the Moon's or Earth's shadow reaches the other body. *Lesson, questions, and flashcards written for this dataset. Reference facts were studied in the supplied Astronomy and Moon-motion records.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [The solar system](https://lightmysky.com/learn/science/the-solar-system-mt_5l7iGkf1Tp) - [Earth & Space Vocabulary](https://lightmysky.com/learn/science/earth-and-space-vocabulary-mt_LQt4vnKeB4) ## Optional connections - [Earth's rotation and day/night](https://lightmysky.com/learn/science/earths-rotation-and-day-night-mt_q15w--Fb5H)