The moon is balanced about it’s own center of gravity, that would shift in this case and parts of the moon that were in compression would now be under tension. I’m not sure about moon rock, but many things that can withstand enormous compressive forces fail easially in tension - so WAG # 1 the moon would fall into a big ‘lump’.
The second thing to consider is the pressure that the moon would exert on the earth (yes this goes both ways) The actual PSI that the moon is exerting on the earth because of the mass of the moon above it will exceed the ability of the crust to support it. My wag is the crust would bend and break as the liquid core is displaced, causing great pressure in the liquid core, which will find it’s way out to the surface.
I wish people would stop using sci-fi books as reference material.
Wikipedia gives a need little chart:
Body Satellite Roche limit (rigid) Roche limit (fluid)
Distance (km) R Distance (km) R
Earth Moon 9,496 1.49 18,261 2.86
So basically, depending on how fluid the moon is, tidal forces will cause it to break up once it is within 1.5 to 2.9 Earth radii of the center.
So I suspect that if the Moon were magically teleported onto the Earth’s surface, it would immediately break apart due to tidal forces.
You’re right of course – but I wasn’t using the book as a reference. My post was in response to a request for a name and author (of, I think, Rocheworld.)
OK. Thanks for the information; that’s what I was originally looking for!
The numbers are amazing. The moon is 3500 km across. The ocean is about 4 km deep. You might as well drop it on antarctica, which is 25km closer to the center. Also the space shuttle orbits at a height of only hundreds of kilometers, so it will have to fly around the moon, looking up at it at an angle pretty much the same as us unlucky ground dwellers. As for the ISS, well Bush said he wanted a base on the moon.
You know, it never fails. Someone suggests an innovative idea, and instantly it meets with knee-jerk opposition. I say let’s give it a chance and see how it works out. If we don’t like it, we can always put it back where it was. Sheesh! Live a little!
Not the one you were thinking of, but Italo Calvino’s collection Cosmicomics includes a short story called “The Distance of the Moon.” It’s set in a mythical time when the Moon’s orbit was so close that when it approached, you could climb up on a ladder, jump up, and float up to it and spend the afternoon there. But it’s moving farther away, and it gets harder to get there or back. He tells a charming little romantic tale of love and longing between the earth and the moon.
I highly recommend the book. Each witty little story starts with a scientifically accurate fact about the formation of the universe, the solar system, or life on earth, and tells a tale about how it affected the people (with names like Qfwfq and Mrs. Vhd) who were around back then.
I did some rough, back-of-the-envelope calculations. The moon in that configuration has about 10^30 joules of potential energy. Gravity will almost immediately compress the two bodies into a single spherical mass. (I’m guessing it wouldn’t take more than a few hours – at that scale solid rock will simply behave like a fluid.) That means most of that potential energy will be converted to heat. That’s more than enough energy to turn the entire crust of the new body molten.
Even without the kinetic energy of a high-speed impact it would be the end of all life. In fact, the resulting new planetary body in Earth’s orbit probably wouldn’t even retain any traces of our current continents, let along any evidence that humanity once existed.
???
What do you mean by this? Neither Venus nor Mercury are “tidally locked” with the sun in the usual meaning of the phrase ( meaning that the same face of the planet is always toward the sun, as the same face of the moon is always toward the earth). There was a time when it was believed of Mercury, but that ended back in the 1950s. I don’t recall ever reading it to be believed of Venus.
Well, Mercury does have a harmonic lock to the Sun, and Venus is almost locked to the Sun, and would be, except that there’s a harmonic lock to the Earth, of all things, holding it back.
With respect to Mercury, I’m aware that the planet is not synchronously tidally locked with the Sun; however, it does have a “3:2 spin-orbit resonance,” which of course is no coincidence, and since the resonance is due to solar tidal forces, I would argue that it is a type of a tidal lock (though not a synchronous one, I grant).
With respect to Venus, it’s orbital and rotational periods are very nearly the same. This is likely due to solar tidal forces. A hypothesized reason for why they are not exactly the same is tidal forces from the Earth.
I think it is no coincidence that the two planets closest to the Sun apparently exhibit various forms of solar tidal locking.
