We brought back 380 kg of rocks from the moon. Could this be the reason the moon is receding?

Question

The 380 kG was taken from another question that was asked recently, and accounts for the total weight of all the missions. Independent of that, I read in these forums that the moon is moving away the earth at 2 or 4 cm per year. Are these related? The distance to the moon is measured with a corner reflector and lasers.

Answer 1

You might be thinking that, since the moon is "lighter" by 380kg, the earth's gravitational pull on it is less, and therefore it's gradually drifting away.

There are a couple of problems with that idea:

1. First, the Apollo missions have actually made the moon _heavier_. Yes, we did take all those rocks, but we _left_ six Lunar Modules there (plus a few cars (rovers) and a bunch of equipment), and those weigh a lot more than 380kg.

2. Changing the mass of an orbiting object does not change its orbit. This is an extension of the gravitational principle that all things (light or heavy) fall at the same rate. Even if you cut the moon's mass in half, its orbit would stay pretty much the same.

In any case, the cause of the moon receding is pretty well understood. It's related to the motions of the tides on the earth. It is also related to to the slowing-down of the earth's rotation.

Answer 2

The sad truth is, is that the moon is moving away. However, it is not because we took 380kg from it. You have to keep in mind that gravity affects almost everything. I don't really know if gravity is effecting the distance of the moon from the earth, but I would think it does. The fact that we are taking some rocks from it, wouldn't affect it that much. You see, a couple of cm may not seem like a lot, but for a planet moving like that, it is. And the way that we can measure the moons distance is with satellites, and some calculators. And yes, I do believe lasers are involved. It would be really hard to measure something like that so precise without lasers being involved. And one last thing-- you have to keep in mind, that planets are moving all over the place all of the time. Planets, and stars that once orbited objects now have flown into the depths of space. Everything in space is moving. Eventually, the solar system that we know now will come apart, and form a new one. But thats a long time away.

Answer 3

No relation at all. 380 kg of rock taken from the moon is a tiny tiny tiny tiny tiny fraction of a tiny tiny percent of the moon's mass (it is 7.3 x 10^22 kg in mass).

The moon is receding due to the conservation of momentum in the Earth/Moon system - friction of the tides caused by the moon are very gradually slowing down the Earth's rotation, and to maintain the total momentum of the whole system something has to move farther away, and the only object that can move farther away is the moon.

Answer 4

No. All the answers above say why the answer is no.

All I have to add is a little humor: 380 kg of rocks taken from the moon is why the moon can never be "full" again. lol.

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Answer 5

No, the moons been moving like that since the beginning of earth afaik, and eventually it will actually break loose (billions of years time i think)

Answer 6

No, as long as the moon has been around, it's been drifting. This has nothing to do with out trip to the moon.

Answer 7

Actually when each moon lander departed it left behind its lander portion and traveled to orbit rendezvous with the command module thereby leaving more mass than they took away.

Answer 8

no, the moon has been moving away since it first became our satellite

Answer 9

Do we actually have a moon I tough that it was gonne here in LA its hard to see it and your question is too hard for me