What would be the effect of mining the moon for raw materials and bringinng to Earth on orbital period etc?

Question

Would the moon move further away or closer? Would the month increase or decrease?　Would the day increase or decrease? I'm a Physics teacher so please feel free to use Physics in your response..

Answer 1

In practice, of course, the amount of material transferred would be so small compared to the mass of the Moon that the effect would be negligible. If you could detect a result, it would be a slight increase in the distance of the Moon and the length of the month. You can think of it in intuitive terms as moving mass toward the center of a rotating system. To conserve angular momentum, the rotation must speed up, and that means the orbital distance and period must increase. You can see the math here http://relativity.livingreviews.org/open?pubNo=lrr-2002-2&page=articlesu9.html worked out in the context of a binary star system, but still applicable, I think.

Vincent has raised some interesting points about the long-term effects on system dynamics, which will somewhat counter the immediate effect.

Answer 2

Well, I've got a theory..... but I don't know quite how accurate it would be, as I only had a couple physics classes and no astro-physics.

Theoretically, it would stay the same, as the speed of gravity has nothing to do with weight.... an apple will fall at the same speed as a bowling ball. Following that line of thought, the moon is already traveling at a certain speed (as are all the artificial satellites around earth), so removing anything or adding anything to it won't change that unless it affects wind resistance (which it wouldn't, since there's no wind in space) or forces a different speed of the moon (which I don't believe changing the mass would since it's already in motion... I believe it would need another force like a lot of blasting off from the surface).

Although I don't think I've ever read that there's any usable minerals up there... just rocks. I don't think there would be enough usable material to make the trip (fuel, training, building facilities, etc) worth it.
The month would stay exactly the same because that's not based on the moon... otherwise every month would be apx 28 days. Days, months, and years are all based on the earth, not the moon, so none of that would change. Even if the moon changed speed or distance from the earth, it would just change the lunar cycles (including the tides) and when eclipses involving the moon would be.

In short/summary, the actual removal of any minerals wouldn't change much of anything with the moon, but the landings and blast offs might change it slightly....... I think.
As a Physics teacher, I'm not sure if you're asking opinions or seeing how hard the question would be on a test..... but I'd be curious if I'm actually right. ;-)

Answer 3

The effect of net mass loss on the Moon should have no effect on the kinetic energy of the mass left behind, so it should not be affected at the first degree.
However, whith less of a mass on the Moon would come less of a gravitational pull on the Earth, and therefore less of a tidal bulge. A smalle bulge would mean less momentum transfer from the Earth to the Moon, and therefore a lessening of the rate at which the Earth's spin is reduced, and a lessening of the rate at which the Moon is receeding. Note that the trends are not reversed, just that their rates are reduced.

That said, there is one thing that needs to be looked at: the momentum transfer for the mass that is lofted from the moon itself to bring back to Earth, and the way this is accomplished. Launch in one direction using mass drivers, and you give a reaction momentum to the Moon that may be accelerating it in its orbit (and thus making it receed) or tries to oppose that motion, making the Moon either receed slower, or if enough mass is involved, might even reverse the current drift.

Days are getting longer, because the Earth's spin is reducing because of the Moon's tidal effect. At the same time, months are getting longer, since the Moon gets progressively further, on an orbit that takes longer to complete. Mining the Moon would only change the rate of change, not the fact that there is a change in the first place.

Answer 4

The Center of Gravity for the moon and Earth would be the same with respect to the sun. But the moon's orbit will increase in radius due to the space ship "pushing" Earth away from the moon (newton's 3rd law) at take off and landing. And the space ship will likewise push the moon from the earth, although this "pushing" is so miniscule, it might as well be ignored.

The days will increase in time (it already has been doing this) due to tidal drag from the moon. Still minsicule.

Answer 5

The moon as no effect on the length of the days. That is determined by the rotation of Earth. I doubt the length of the month would change either, as we have developed a fairly accurate calendar.

Are you really a teacher? I don't want to sound mean but most people know (I hope) that the moon does not affect the days.

Answer 6

I hate to be insulting, but YOU'RE A PHYSICS TEACHER?

First of all, what raw materials would we mine from the moon? Isn't the moon composed mainly of lightweight dust and rock? And how could we possibly make enough of a dent in the moon's weight to affect either its gravity or its orbit? And the moon has NOTHING to do with the length of the day--that's all interaction between the sun and the earth. But then, I have no clue what you mean by "bringinng to Earth on orbital period etc" so maybe I'm missing something.

Answer 7

Yea Im constructive that there is a large number of an incentive to bypass mine fantastically much 4 hundred,000 km away. to boot what's the moon even made up of interior the 1st place? "in terms of factors, the crust is composed on the whole of oxygen, silicon, magnesium, iron, calcium, and aluminium." those are quite a few the main substantial factors on the earth!! Mining the moon could be like the perfect economically stupid selection ever made.

Answer 8

you're a physics teacher and you're asking a bunch of yahoo nuts???
...hmm...I dont think the moon would move at all. I think man would ruin the moon as they have ruined the earth, ...but ...what do i know, i'm not the teacher.
A rather odd question though

Answer 9

I don't think the result would be measurable. It is very unlikely we could afford to transport enough mass and, being humans, we probably would leave as much garbage as we would mine.