---
title: "Phases of the Moon"
license: CC-BY-SA-4.0
license_url: https://creativecommons.org/licenses/by-sa/4.0/
source: https://en.wikipedia.org/wiki/Lunar_phase
source_license: "CC BY-SA 4.0 (Wikipedia)"
attribution: "Summary by iinventedlight (AI-assisted). Source: Wikipedia, \"Lunar phase\" (CC BY-SA 4.0 (Wikipedia))."
condensed_by: "iinventedlight (Grok Bot, AI-assisted)"
fact_checked: 2026-10-14
date: 2026-10-14
status: reviewed
reviewed_on: 2026-10-14
category: science
checked_on: 2026-10-14
sources:
  - id: S1
    title: "Lunar phase"
    publisher: Wikipedia
    url: https://en.wikipedia.org/wiki/Lunar_phase
    accessed: 2026-10-14
    license: "CC BY-SA 4.0 (Wikipedia)"
---
# Phases of the Moon

## Summary
Phases come from how much of the Moon's sunlit half we see as it orbits Earth, not from Earth's shadow. A full cycle (new to new) averages about 29.5 days.

## Facts
- id: F1
  claim: The four major phases are new moon, first quarter, full moon and last quarter; between them are waxing/waning crescent and gibbous.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
  checked_on: 2026-10-14
- id: F2
  claim: A full cycle of phases (synodic month) averages about 29.5 days.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
  checked_on: 2026-10-14
- id: F3
  claim: Phases are not caused by Earth's shadow; they reflect how much of the Moon's sunlit side faces us.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
  checked_on: 2026-10-14
- id: F4
  claim: Earth's shadow on the Moon is a lunar eclipse, possible only at full moon near an orbital node, since the Moon's orbit is tilted about 5 degrees.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
  checked_on: 2026-10-14
- id: F5
  claim: The Moon orbits in 27.3 days (sidereal), but phases repeat every 29.5 days because Earth also moves around the Sun.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
  checked_on: 2026-10-14
- id: F6
  claim: In the Northern Hemisphere a lit right side means waxing; the view is flipped in the Southern Hemisphere.
  confidence: medium
  date: 2026-10-14
  sources: [S1]
  license: CC BY-SA 4.0
  checked_on: 2026-10-14

## Pointers
- answers: Full official guidance beyond this summary
  where: https://en.wikipedia.org/wiki/Lunar_phase
  access: open, no account