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Orrery: Sun, Earth, and Moon


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This is a Lego orrery built primarily out of Technic, with a studs out model of the earth. It is motorized and includes kinematics for:
  • Earth rotating on its axis
  • Sun rotating on its axis (every 36 earth days)
  • Moon rotating around the earth (every 25 earth days)
  • Earth rotating around the sun (every 327 earth days)
  • Earth's tilted axis (22.5º), held fixed as earth orbits the sun to model seasons

I built this model for my three year old who is always asking "why?" Almost daily he would ask why it is getting dark outside, and this model has been a fun way to explain celestial phenomena.

This model captures day/night cycles, changing of the lunar phase, and seasons.

The are two mechanical switches, one on either side of the orrery.
  • Switch 1 is two-way. It engages/disengages the rotation of the earth around the sun. When disengaged the earth can be manually rotated (while the tilt is still automatically maintained) to quickly explain the different seasons.
  • Switch 2 is three-way. It toggles between high/low speed motor drive or disengages the motor drive altogether. When disengaged, the earth can be rotated by hand to study how the moon moves with each passing day.

The model of the earth includes low resolution land masses for the 7 continents, and there is an optional simple model of a geostationary satellite orbiting above the pacific ocean.

The sun is an icosahedron built entirely out of Technic.

The Powered-Up battery pack counterweights the earth and its supporting arm.

Piece count: 1042

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