How do Moon phases work on a flat Earth?
Sun and Moon · Updated
According to the Flat Earth Society, the Moon is a sphere about 32 miles across, several thousand miles above the flat Earth, and half of it is lit by the Sun. Its phases come from the Sun and the Moon moving up and down and exchanging heights as they circle the North Pole, so the lit half points towards or away from you.
The Flat Earth Society explanation
The Flat Earth Wiki describes the Moon as a revolving sphere 32 miles across, several thousand miles above the Earth. Like on the globe, the Sun lights half of it. What changes is the geometry: the Sun and the Moon “are constantly wobbling up and down and exchange altitudes as they rotate around the North Pole”.
- First quarter: the Moon and the Sun are at the same altitude, and half of the face you see is lit.
- New Moon: the Moon is below the Sun and near it, so its lit side faces away from you.
- Full Moon: the Moon is above the Sun and opposite it, so its lit side faces you.
The cycle takes about 29.53 days, which the wiki describes as the cycle of alternating altitudes.
How FlatAtlas shows the Moon
FlatAtlas places the Moon above the point on Earth where it is overhead right now, at the height of the model you choose, and draws its real phase from astronomy: the lit fraction and the direction of the bright side. The Flat Earth Society model in FlatAtlas uses one height for the Moon and the Sun, 4,800 km, because the wiki gives no figures for how much their heights change.
Why the Moon looks upside down in the south
Seen from the southern hemisphere, the Moon appears rotated compared with the north. The Flat Earth Wiki explains this by observers standing on either side of the Moon, like people on opposite sides of an arrow hanging above them: from one side it points up, from the other down.
What you can check
- The same phase everywhere. At any moment the Moon shows the same lit fraction from every place on Earth; only its orientation changes. Compare with a friend on another continent, or check the phase in FlatAtlas for two places.
- Full Moon opposite the Sun. At full Moon, the points below the Sun and the Moon are on opposite sides of the Earth. On the flat map they end up on opposite sides of the North Pole. Move the time in FlatAtlas to the next full Moon to see it.
- The Moon’s size. In the model, a 32-mile Moon 4,800 km up would look about 0.6° wide overhead and smaller as it moves away. The real Moon looks about 0.5° wide wherever it is in the sky.
Frequently asked questions
What causes the Moon's phases on a flat Earth?
The Flat Earth Wiki says the Sun lights half of a spherical Moon, and the phases come from the Sun and Moon wobbling up and down and exchanging altitudes as they circle the North Pole.
How big is the Moon on a flat Earth?
The Flat Earth Society gives the Moon a diameter of 32 miles (51 km), the same as the Sun, several thousand miles above the surface.
Why does the Moon look upside down in the southern hemisphere?
The Flat Earth Wiki explains it by observers standing on either side of the Moon: from one side it looks right side up, from the other upside down.