--- title: "Phases of the Moon" description: "Explain the phases of the Moon as the changing angle of sunlight on the lunar surface as seen from 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: 2026-10-19 --- > **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 the phases of the Moon as the changing angle of sunlight on the lunar surface as seen from 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 approximately 28 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 does not make its own light. You see it because sunlight bounces off it and reaches your eyes. At any moment, half the Moon is lit by the Sun and half is dark, just like Earth has day and night. As the Moon orbits Earth, the angle between the Sun, the Moon, and you keeps changing. That changing angle decides how much of the lit half you can actually see, and that is why the Moon seems to change shape. *(drawing: The Moon's cycle, about 28 days start to finish: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Waning Crescent, then back to New.)* **Example.** Two weeks ago, Amara saw a thin crescent Moon low in the sky. Tonight she looks up and sees a full circle of light. Nothing happened to the Moon itself. Over those two weeks it moved along its orbit, so the sunlit part facing Earth grew bigger each night until she could see the whole lit half: a full moon. **Tip.** It's tempting to think Earth's shadow causes the phases, covering part of the Moon each night. That's not it. Earth's shadow only matters during an eclipse. The nightly phases come from the angle of sunlight and the Moon's position, nothing else. Sometimes the Sun, Moon, and Earth line up almost exactly, and that's when eclipses happen. In a solar eclipse, the Moon slides between the Sun and Earth, and its shadow blocks sunlight from a small part of Earth during the day. In a lunar eclipse, Earth slides between the Sun and Moon, and Earth's shadow falls across the Moon, often turning it a dim reddish color. **Recap.** Moon phases come from the changing angle of sunlight as the Moon orbits Earth, and eclipses happen only when the Sun, Moon, and Earth line up in a row. ## 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) - [Earth's rotation and day/night](https://lightmysky.com/learn/science/earths-rotation-and-day-night-mt_q15w--Fb5H)