Earth and Moon Orrery

The Earth is blue and the Moon is zinc, so the colours are as close as they can be to the real Earth and Moon. The Earth is four times the diameter of the Moon, the same ratio as the real Earth and Moon. The Earth rotates 28 times for one orbit of the Moon; this is achieved with a 7:1 gear reduction multiplied by a 4:1 gear reduction. The distance between the Earth and the Moon is at a scale of 1:5 billion, so in terms of scale only, the orrery is probably the smallest ever entry for the Geoff Carter Cup.

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