A backyard sky lesson in 3D
In one night the Moon moves west with all the stars. Each night it slips back east and changes shape.
Your spot stays on this page. Nothing is saved or sent.
Second place
Drag to turn. Pinch, or click and scroll, to zoom.
Keys: Pplay,.an hour back or on[]a night back or on123the three viewsGsee through the groundTtonightOn the 3D view, arrow keys turn it and +−zoom.
Line of sight: the Moon is upThe Moon is below your horizon, so the line goes through EarthWhere the Moon is straight overheadSame clock time on other nightsEarth turns east
Press Compare and pick a second place. This tab then shows what changes between the two skies, and the second place in numbers.
Earth spins once a day. So the Sun, the Moon and the stars all slide across the sky from east to west, about 15° every hour. They all turn around one axle that points at the North Star, or at the empty south pole of the sky.
The Moon also travels around Earth, once a month. Each day it moves about 13° east against the stars. It moves 12° to 15°, faster when it is closer to us.
When Earth has turned once, the Moon has moved on. Earth needs to turn about 50 more minutes to catch up. The real wait runs from about 30 minutes to well over an hour, depending on how steeply the Moon's path meets the horizon. Try "Why does the Moon rise later?" in the space view.
Over two weeks the Moon's path goes from high in the sky to low, then back. In Layers, set "Paths on other nights" to a week each way to see the paths fan out.
The Sun always lights half of the Moon. As the Moon goes around us, we see more or less of that lit half. Full moon rises around sunset. New moon rises and sets with the Sun, so you can't see it.
Not to scale: in the backyard, the Moon and Sun are drawn about 10 times bigger than they look. From space, the Moon is drawn 11 times closer to Earth than it really is, unless you turn on "Show true distance".
A degree (°) is a small step of sky. From the horizon to straight overhead is 90°, about nine fists at arm's length.
At the same clock time each night, the stars themselves sit about 1° further west. A day by the stars is 4 minutes shorter than a day by the clock. That is why one full turn of Earth takes 23 h 56 min.