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I'm talking about a massive ship, let's say half the mass of the Moon, within the Hill sphere, so that is not snatched up by the Sun and can orbit around Earth.

Assuming it's positioned as far as it can possibly be and starts orbiting around our planet, what would the effects be on our planet?

Would it mess up the tides? Would it send the Moon away? Would it change the behavior of animals? Is it even possible to dream a scenario like this and follow the rules of physics?

Orpheus1844
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  • @Abigail That's an answer, not a comment... ;-) Ping me and I'll come back and upvote. – Fabby Sep 23 '18 at 15:12
  • @Fabby, Hi. I edited my question. Thanks! – Orpheus1844 Sep 23 '18 at 15:25
  • @Renan - I don't see how this is a duplicate of that question - the asteroids in that question are 1. much lighter (orders of magnitude) and 2. just passing as opposed to orbiting, so I don't see how it's clear that they're the same question – Mithrandir24601 Sep 23 '18 at 15:29
  • @Mithrandir24601 is your nick inspired on Drowtales? Anyway there are equations in that question, just input mass on them and see what effect you get. – The Square-Cube Law Sep 23 '18 at 15:38
  • Too close, tidal forces will be noticeable. Far enough, it may interfere with the moon's orbit. It may be wiser to enter into orbit at one of the Earth-sun Lagrange points L4 or L5. – Christmas Snow Sep 23 '18 at 16:35
  • Or really any of the mentioned duplicates on that question, or the related questions! – dot_Sp0T Sep 23 '18 at 17:14
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    This is the scenario of Fritz Lieber’s novel The Wanderer, so I’d suggest finding and reading a copy. – Mike Scott Sep 23 '18 at 19:41
  • @Renan Yeah, there are equations in that question and sure - they're the same equations you'd use to answer this one... That however, doesn't make it a duplicate - there are just a few equations that solve virtually all classical orbital force problems, yet it's not like we mark all of those as duplicates. This is essentially as getting a number out the end doesn't tell you very much - it's the conclusions drawn with that number that answers the question, not the number itself – Mithrandir24601 Sep 23 '18 at 22:40

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Yes it will mess with the tides and that would be positively moon like. The tidal chaos could potentially cause massive floods. Have you ever seen two waves coming from opposite directions meet one another. the resultant wave is often a very sharp jump up in shallow depths. That could really be quite nasty. Not Tsunami like, but very fast very high tides. So fast moving that many estuary channels would reshape themselves and low lying flats surrounding these estuaries would become inundated.

There is also the possibility of the ship eclipsing the sun. That is most likely to drive the wildlife nuts. It could potentially disturb mating habits at a stretch. And if the ship eclipsed the sun often enough it could cause Global Cooling. But it would have to find a way to position itself in front of the sun on purpose regularly to do that. Which is difficult if you want to stay in orbit.

As for the moon, the ship and the moon would be gravitationaly attracted. So potentially it could dramatically alter the moons orbit, but what that would look like in real terms I couldn't say with certainty. I suppose it would give the moon a more elliptical orbit which could cause a catastrophic collision with the earth(?). But that seems a little far fetched.

The most logical orbit I can think of for this half moon mass ship would be half the distance between the moon and the earth away from the earth.

OhNoNotScott
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    Mr. Roland Emmerich, is that you? (1) We already have neap tides and spring tides, due to the interaction of the tidal forces of the sun and the moon. No massive floods. (2) It's smaller than the moon. It won't eclipse the sun, definitely not more than the moon already does. (3) Eclipses are rare. Wildlife doesn't care about them. (4) The orbit can have any radius, as the captain of the ship wishes; Kepler's second law applies. (5) The exact results on the moon depend on the intentions of the captain. (6) I would pay to see the movie; for now, +1. – AlexP Sep 23 '18 at 17:14
  • I agree with you @AlexP. The ship can have any orbit the captain desires, and it is for this reason that it could POTENTIALLY cause tidal chaos and potentially eclipse the sun but it would very much depend on the orbit chosen. I guess I'm assuming it can travel across the galaxy and probably do all sorts of weird maneuvers. – OhNoNotScott Sep 25 '18 at 15:44