The Earth and the Moon, drawn to scale, are two small worlds separated by a gap far wider than either, the only stretch of space people have yet crossed.
About The Earth and the Moon
Pictures in books usually squeeze the Moon close to the Earth. At true scale the gap is many times the Earth’s own width, and the pair look lonely in it. The Moon always turns the same face towards us, because tides raised by the Earth long ago slowed its spin until it matched its orbit.
Those same tides are still at work: they slowly lengthen the Earth’s day and push the Moon very gradually outward. The Moon is the only other world humans have walked on, during the Apollo missions, and its distance is measured precisely by bouncing lasers off reflectors they left on its surface.
What you see in the piece
This is the first rung of the zoom, starting just above the Earth’s surface, near the orbit of the ISS. The Moon is lit only by the Sun, so its phase in the piece is the phase it really has.
Questions
How far is the Moon from Earth to scale?
Much farther than most diagrams suggest: the gap between them is many times the Earth’s width, yet it is the shortest hop between worlds in the whole zoom.
Why does the Moon always show the same face?
The Earth’s tides slowed the Moon’s spin until it turned once on its axis for every orbit, so the same side always faces us.