ELI5: Why does the moon move further across the sky every day?

  1. Because the Moon is orbiting the Earth every month, in addition to the Earth rotating every day. By the time the Earth rotates once, the Moon has moved ~1/28 of the way around its orbit, which is a big enough difference to be visible in the sky.

  2. The moon takes 27 days, 7 hours and 43 minutes to circle the Earth / 29.5 days to go from one full moon to the next. Each day it appears about 50 minutes behind the last. It's circling the Earth so it doesn't stay in the same spot.

  3. It's orbiting very close to us so it seems to move relatively quickly against the background of stars. It moves its own width every hour in front of the stars. Actually the stars go around the sky fastest, returning to the same position every 23h56m. The sun comes next at 24h00m and the moon's at 24h50m. So, in some ways, the moon is actually the slowest-moving object in the sky.

Leave a Reply

Your email address will not be published. Required fields are marked *

Author: admin