Supposing Jupiter’s orbit had destabilized, such that it crossed Earth’s orbit. Are there any sets of circumstances where it could capture the moon without damaging the Earth?
Define “damage.” Tides are pretty important, for one.
Okay, how about this:
Scenario 1: Jovian gravity causes the moon to fall into Jupiter. What is the minimum adverse affect to Earth?
Scenario 2: Jovian gravity captures Earth’s lunar body and the moon now orbits Jupiter, but does not fall in. What is the minimum adverse affect to Earth?
I am not an astronomer in any way but I think that Jupiter coming that close to Earth would be devastating to our planet.
Not only would the loss of the moon it itself completely destabilize ecosystems through the loss of tides but having a huge mass like Jupiter fall into a lower orbit would alter the orbits of the other planets as well. I don’t know if it would rip the Earth apart but it would certainly be civilization changing.
nm.
Doing some back-of-the envelope calculations, I tried to assume that Jupiter was on the far side of the moon, just far away enough to exert the same gravitational pull on it that Earth does. Obviously it would have to be somewhat closer than that to actually “pull away” the moon. This would be about 7,000,000 km, or about 18x more than the distance between the Earth and the moon.
In that situation, the gravitational pull on the Earth from Jupiter would be over 60x the gravitational pull of the Moon, and about 1/3 of the pull we get from the Sun.
Surprisingly, the tidal forces would “only” be 4-5x greater than the forces from the Moon, however. That’s because the tidal forces depend on the ***difference ***in the gravitational pull on the center and surface of the Earth. So the further away your gravitational source is, the less significant tidal forces become.
That said, increasing the tidal forces by 4-5x would be devastating, at least wiping out coastal cities, and causing major earthquakes around the world. But the biggest problem would be the effect Jupiter has on our orbit. We would likely be thrown into a more elliptical orbit, causing the Earth’s climate into seasons of thermal extremes, wiping out any remaining humans.
Then again, my math might be wrong.
If Jupiter positioned itself on the far side of the moon at a distance to provide the exact gravitational pull on Luna that Earth does, wouldn’t the moon go shooting out in a straight line tangent to its orbit?
I mean, in addition to all the environmental disaster that the proximity of Jupiter would bring to us.
No, it would fall into orbit around the more massive body (Jupiter). The gravitational pull is a function of (mass/distance^2). If it moves in a straight line from the gravitational equilibrium point, the rate of change of distance would be less for the farther object, therefore it’s gravitational force would decrease slower and the Moon would be pulled towards it.
However, in an ideal situation where the Earth and Jupiter were exactly the same mass and there were no other outside forces. I think the Moon would bounce back and forth like the pocket of a slingshot.
If Jupiter was in a position to pull the moon away from the Earth, would there be a possibility of Earth itself becoming a Jovian moon, too?
Loss of the moon wouldn’t result in the loss of tides. We would still experience solar tides, so on average the tides would be about the half the magnitude they are today. Of course the total variation would be much less, with all tides being uniformly average with no spring tides or nap tides, and the tides would occur on a 12 hour cycle rather than a ~28 day cycle. The effect on ecosystems would be minimal. Some species specifically adapted to the extreme parts of the intertidal zones would perish. Some specific areas would experience greatly altered tide heights due to effects of geography and prevailing winds, but for the most part the natural world would be unaffected.
IANARS, but I don’t see how that could happen. If Jupiter and the Earth are in the same orbit, but far enough away from each other to not cause massive tidal waves on the Earth, it seems impossible for the moon to oscillate between them. Once it gets closer to one or the other, it should “stick” to it.
If Jupiter is orbiting inside or outside the orbit of the Earth, then it will be going around the sun faster or slower than the Earth, and will soon be far ahead or behind. There is no way that they can “share” the moon for very long.
It also occurs to me that if Jupiter were close enough to match the earth’s attraction to the moon, taking the 7 million km figure calculated above as correct, then several of Jupiter’s moons might slam into the earth, which can’t be a good thing.
Which is why I said “in an ideal situation”, i.e., if Earth and Jupiter were EXACTLY the same size/mass, and EXACTLY the same distance from the Moon, and had no external forces. This wouldn’t happen in the real world, though.
Would it be possible to set Jupiter’s orbit in such a way that it captures the moon on one pass (in the process altering the earths orbit), and then in a second pass a few months later corrects the orbit? Then we would only have a few months of weird weather. Bonus points if at the end of this Jupiter and the moon leave the solar system entirely so that it doesn’t risk screwing with the earth on any future passes.
ETA: I guess the other way it could work is for Jupiter to come screeching in really really fast so that it doesn’t have time to alter the earth’s orbit significantly.
I think the effects of losing the moon, regardless of how it happens, would be much more serious than “a few months of weird weather”
So your “ideal situation” has no Sun? Somehow that doesn’t seem ideal to me.
Suppose we only alter Jupiter’s orbital eccentricity (and nothing else). Can Jupiter cross Earth’s orbit?
If so, what is the maximum velocity at which it can cross the Earth orbit?
At this speed, what is the shortest duration of time under which Earth is significantly affected by Jovian gravity?
If Jupiter swallows the moon, but misses the Earth, what is the minimum peak Jovian gravity experienced by the planet Earth?
If Jupiter came close enough to capture the moon, what would the effect of Jupiter’s magnetosphere on the Earth be? Wouldn’t we be fried by the radiation belt?