What would the moon look like if it was only 400 km away?


Have you ever wondered what it would look like if the moon was closer to the Earth? How about if it was a lot closer — like just one tenth of one per cent of its current distance?

That's what this cool animation shows, as the moon rises and sets as if it orbited around Earth at the same distance as the International Space Station:

Did the looming moon set off a bit of instinctual fear there? It sure did with me!

Some facts: Orbiting at 416 km, the moon would go around the Earth in just over 90 minutes, and since it would be orbiting faster than the Earth rotates, we would see it rise in the west and set in the east. The video is sped up for dramatic effect, but it's really not that far off on the time the moon would take to cross the sky. Rather than taking around 12 hours, like it normally does, it would rise and then set in just a little over 10 minutes. Also, the surface of the moon stays visible, even when it's eclipsing the sun, because of Earthshine. That's except for the very centre of the moon, though, because the immense shadow it's casting on the Earth isn't reflecting any light back.

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Of course, we'd never actually see the moon like this. If orbited that close, the tidal forces between the Earth and the moon would devastate the planet and we probably wouldn't be here. However, physics would never allow the moon to form at that distance anyway. It would have to stay at least 9,500 km away or it would be torn to shreds and end up as a ring orbiting the planet.

Still it's fun to contemplate these things, though, especially when you can see it animated before your eyes.

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