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🌙 How far away is the Moon

Measure the Moon's changing distance, compare it with familiar journeys, and see how scientists know where the Moon is.

2
lessons
~10 min
to learn
Adults
level
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What you’ll learn

  1. A surprisingly long gapExplain the average Earth–Moon distance using scale comparisons and distinguish it from the Moon's diameter.The Moon averages 384,400 kilometers away, roughly thirty Earth diameters, but its elliptical orbit makes the distance vary.
  2. How we know the numberDescribe how laser ranging measures lunar distance and why the Moon is slowly receding.Timed laser pulses reflect from lunar panels, turning round-trip travel time into distance and revealing long-term tidal evolution.

Questions this course answers

What does 384,400 kilometers describe?

384,400 kilometers is the average distance from Earth's center to the Moon's center. The elliptical orbit means the actual distance varies.

Match each term to its meaning.

Perigee and apogee describe distance. A phase describes illumination.

Why does lunar laser ranging divide the light's travel time by two?

The measured time is a round trip. Dividing by two gives the one-way time used to calculate distance.

Give the careful answer to How far away is the Moon?

A good answer gives the useful average and important range because the Moon's orbit is elliptical.

Grounded in trusted sources

  • NASA Science — Moon Facts: https://science.nasa.gov/moon/facts/
  • NASA — Lunar Laser Ranging: https://science.nasa.gov/solar-system/moon/lunar-laser-ranging/
  • NASA Space Place — What Is an Eclipse?: https://spaceplace.nasa.gov/eclipse/en/
  • U.S. Geological Survey — The Moon: https://www.usgs.gov/programs/astrophysics-geophysics-and-geodesy/science/moon
  • National Institute of Standards and Technology — Measuring the Moon with Lasers: https://www.nist.gov/news-events/news/2017/07/measuring-moon-lasers

Every Wunder lesson is built from real, reputable sources — never invented.

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