edubun
English
English한국어EspañolPortuguêsFrançaisDeutschItalianoNederlandsРусскийBahasa Indonesia日本語
Home›Astronomy and space

The Moon

The Moon is 384,400 km away on average and shows us the same face all month. Move the 3D Sun, Earth and Moon through one 29.53-day cycle, line them up for eclipses, and watch the tides follow.

Progress

About this course

The Moon is called simply "the Moon" because for most of history nobody knew other moons existed. That changed in 1610, when Galileo found four moons circling Jupiter. The Latin name Luna survives in the word lunar. The Moon is 384,400 km away on average, and it is drifting away from Earth by about 3.8 cm a year. The tides are the reason. Because the ocean bulges run slightly ahead of the Moon, they pull it forward along its orbit, and the friction slowly brakes Earth's spin.

The seven units start with size and distance, where about 30 Earths fit in the gap. Phases come next: from one new Moon to the next takes 29.53 days, about two days more than one trip round Earth. The unit on the same side explains that the Moon turns once on its axis in 27.3 days, so we never see the far side, which NASA says is misleading to call dark. Lunar eclipses use Earth's shadow, about 9,200 km wide at the Moon's distance. Solar eclipses depend on the Sun being about 400 times wider and 400 times farther away. After tides, the final unit covers Apollo, where twelve astronauts walked on the Moon from July 1969 to December 1972 and brought back 382 kg of rock and soil. One story adds Artemis II, launched on 1 April 2026, which looped round the Moon within about 6,545 km. The 3D model shows the Sun, Earth and Moon through one 29.53-day cycle, and you can line them up for eclipses.

Before you start

Nothing is required to start. A picture of where Earth sits among the planets makes the scale easier, so The solar system is a pleasant first step, but this course explains distances, orbits and shadows on its own with a 3D model of the Sun, Earth and Moon.

When you finish

You will be able to explain why about 30 Earths fit between Earth and the Moon, why phases repeat every 29.53 days rather than 27.32, and why we always see the same face. You can tell lunar from solar eclipses and say why a totally eclipsed Moon turns red, explain two high tides a day and spring tides, and outline the six Apollo landings.

  1. 1How big and how far is the MoonAbout 30 Earths would fit side by side in the gap between Earth and the Moon.
  2. 2Why the Moon has phasesFrom one new Moon to the next takes 29.53 days, about two days longer than one trip round Earth.
  3. 3Why we always see the same side of the MoonThe Moon turns once on its axis in the same 27.3 days it takes to go once round Earth.
  4. 4Lunar eclipsesAt the Moon's distance Earth's dark shadow is about 9,200 km wide, more than two and a half Moons.
  5. 5Solar eclipsesThe Sun is about 400 times wider than the Moon and about 400 times farther away, so the two look almost the same size.
  6. 6How the Moon makes tidesMost coasts get two high tides a day, about 12 hours 25 minutes apart.
  7. 7The Apollo Moon landingsBetween July 1969 and December 1972, twelve astronauts walked on the Moon and brought back 382 kg of rock and soil.

Related courses

  • The solar system
    Eight planets, one star, and distances so large that a true-scale model will not fit on any screen. Spin the 3D model, switch to true scale, and compare the planets with real numbers.
  • Stars
    The Sun is an ordinary star 109 Earths wide, and Betelgeuse would hold hundreds of millions of Suns. Compare real star sizes in 3D, place stars on a Hertzsprung-Russell diagram, and follow a star from a gas cloud to a white dwarf, neutron star or black hole.
  • Galaxies
    The Milky Way is a barred spiral more than 100,000 light-years across, and the Sun takes about 230 million years to go round it once. Spin a 3D galaxy, compare spirals, ellipticals and irregulars, meet our neighbours and see how the expanding universe was found.
  • Reading the night sky
    The sky turns 15° every hour, Polaris sits at the same height as your latitude, and the stars rise four minutes earlier each night. Set any place, date and time in the 3D sky dome, with 525 real stars from the Yale Bright Star Catalogue and approximate planet positions.
Sources for this course (16)
  • NASA Moon Fact Sheet (nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html)
  • NASA Moon facts (science.nasa.gov/moon/facts)
  • NASA Moon phases (science.nasa.gov/moon/moon-phases)
  • NASA Tidal locking (science.nasa.gov/moon/tidal-locking)
  • NASA Tides (science.nasa.gov/moon/tides)
  • NASA Moon eclipses (science.nasa.gov/moon/eclipses)
  • NASA Eclipse types (science.nasa.gov/eclipses/types)
  • NASA GSFC eclipse tables by Fred Espenak (eclipse.gsfc.nasa.gov/LEdecade/LEdecade2021.html, eclipse.gsfc.nasa.gov/SEdecade/SEdecade2021.html)
  • NASA SVS Moon Wobble (svs.gsfc.nasa.gov/10836)
  • NASA Apollo program (nasa.gov/the-apollo-program)
  • NASA Apollo 11 mission overview (nasa.gov/history/apollo-11-mission-overview)
  • NASA Apollo 12, 14, 15, 17 mission pages (nasa.gov/mission/apollo-12 etc.)
  • NASA Moon walkers (science.nasa.gov/moon/moon-walkers)
  • NASA Moon exploration (science.nasa.gov/moon/exploration)
  • NASA Apollo samples (science.nasa.gov/science-research/planetary-science/astrobiology/nasas-apollo-samples-yield-new-information-about-the-moon)
  • NASA Artemis II (nasa.gov/mission/artemis-ii, nasa.gov/news-release/nasas-artemis-ii-crew-eclipses-record-for-farthest-human-spaceflight, nasa.gov/gallery/artemis-ii-splashdown-and-recovery).

Checked: 2026-10-17