What is Earthrise over the Moon? (Intermediate)

Background: Adult, stargazer, discussing the orbit of the moon around the earth and the earth and moon orbiting the sun, with some friends. We figured out the "dark side of the moon" but then started discussing earthrise and we couldn't manage it.

When you are on the moon, when and how and why would you see the earth rise and set?

If you are standing on the Moon you will never see the Earth rise or set. The reason is that one side of the Moon always faces the Earth and the other always faces away. So almost anywhere on the Moon you either see the Earth or don't. I say almost anywhere because I should probably add that the Moon sort of 'jiggles' from side to side a bit. A tiny bit more than 50% of the surface is thus visible from the Earth over time and in locations near the edge you therefore might be able to see the Earth go up and down a bit . Without more thinking about it I couldn't say if the Earth would completely rise and set or if you would be able to see/not see part of it all the time.

When you hear about Earthrise over the Moon what is going on is that the picture was taken from a spacecraft orbiting the Moon. Since this is moving around the Moon it is able to see the Earth rise as it moves. There are some pretty famous examples of photos of this phenomenon like the Apollo 8 picture (1968) which is below and the Lunar Orbiter 1 picture (1966).

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Thank you Karen, This was a very interesting exercise!

About the Author

Karen Masters

Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

Twitter:  @KarenLMasters
Website:  http://icg.port.ac.uk/~mastersk/