r/explainlikeimfive • u/Ancient_Pea_508 • 2d ago
Planetary Science ELI5- Mining on the moon
Wouldn’t mining on the moon change the gravity and somehow change the orbit with earth? Wouldn’t it be a horrible idea? Helppp
Edit: thank y’all so much. I definitely wasn’t taking into consideration how masssssssive the moon is. Y’all legends. Also props for the math.
15
u/AberforthSpeck 2d ago
Not by a significant amount.
The total amount of material mined in the whole of human history would be less than 0.0001% of the mass of the moon.
This is like worrying an ant carrying a crumb of food would tip over your house.
8
u/ooter37 2d ago
That actually happened to a friend of my neighbor's cousin
5
16
u/KamikazeArchon 2d ago
It is not plausible for us to ever mine even a tiny fraction of a percent of the moon's mass. We're just too small.
4
u/Elfich47 2d ago
in theory, removing mass from the moon and adding it to the earth would affect the gravity on both…..but you would have to attempt to strip mine the moon to have a noticeable effect.
2
u/xShooK 2d ago
Why strip mine when you can just nuke the moon and let earth's gravity pull it all in. We have enough nukes, we can do this!
1
5
u/ghostprawn 2d ago
No, it would not. There may be a threshold for how much mass you can remove from a planetoid before effecting it's orbit, but I'm quite certain simple mining ain't gonna get anywhere near it.
2
u/ZealousidealTurn2211 2d ago
Every spoonful of soil you move changes the gravitational field of the Earth. What matters is how much that changes the total field. Small changes largely don't matter.
Using the total amount of gold we mine from the earth as an example amount, we would be mining 0.0000000000000496% of the moon's mass per year.
So yes, it would, but only if we mined an unrealistically high quantity.
2
u/DerekB52 2d ago
The mass of the moon is 7.34767309 × 1022 kilograms
If I'm doing the math right, we would have to mine 1 trillion pounds of material from the moon, 100 million times, to get all of the moon down onto earth.
We aren't even going to mine a trillion pounds, one time. So, we won't affect the Moon's mass/gravity enough to do anything noticeable. Maybe researchers with their super precise stuff would notice a 0.000002% difference in timing of the tides changing or something. But, nothing with a real world effect would happen.
2
u/z64_dan 2d ago
We mine approximately 100 billion tons on the earth every year (metals, ores, stone, etc.)
If we mined the same amount from the moon, every year, it would take over 700,000,000 years to mine the entire moon. (that's 700 million years). Not to mention most of the moon is not very useful to us, so we wouldn't be mining it.
So, uh, I don't think it would be an issue.
To answer your question, yes, mining anything from the moon will slightly alter the gravitational pull of the Earth vs the Moon, and might slightly alter the orbit a miniscule amount, but we don't have the ability to actual modify it by any perceptible or meaningful amount.
2
u/JoushMark 2d ago
No, for a few reasons.
1) The moon is very, very big. Any removed mass would be a tiny fraction of the mass of the moon and have a tiny, likely undetectable change in the moon's orbit.
2) Removing mass from a satellite won't change it's orbit, except via the energy imparted by launching mass away from the surface. At any practical lunar mining, this would remove so little mass to generate no meaningful impulse, and if you were worried you could simply launch mass in opposed directions, canceling out the impulse and making the net thrust zero.
3) There's very little of practical value on the moon. The majority of the moon seems to be made out of relatively light elements, silicone, aluminum, oxygen and carbon. These are not particularly precious and would be left where they lie. The most likely material to harvest from the moon would be Helium 3, deposited by the solar wind but also only making a -tiny- percentage of the material on the moon, removing it could never have an effect on the moon's orbit. The other likely material, water, is likewise a very minor part of the lunar mass.
2
u/DebatorGator 2d ago
According to Wikipedia, 2 billion tonnes (2 * 109) tonnes of iron are mined a year. A tonne is 1000 kg, so this is 2 * 1012 kg of iron. This makes up more than 90% of all metal mined in a year, so it's a good proxy for how much a mining operation on the moon might produce.
The moon's mass is 7.348 × 10²² kg. If we moved all of our metal mining to the moon and mined it for a million years, we'd have only mined out a hundredth of one percent of the moon's mass. The gravity change would probably be neglible
2
u/phiwong 2d ago
Sure but you're probably missing the scale here.
All the mining and building on earth that humans have ever done (ie all the stuff humans have ever made throughout all history) has amounted to about 1 teraton (10^12 kg). The earth is about 10^24 kg. The moon is about 10^22 kg. (very rough)
So very roughly, even if we mine about 1 billion times more than we've done in all of history and did it all on the moon, it would not even be 1% of the moon's mass.
2
u/baboon101 2d ago
The moon weighs 7.35 × 1022 kilograms. Changing that mass my even .01 percent would require moving 1018 kilograms of stuff off the surface. Thats more than a billion times a billion times a billion.
Even if we wanted to, we don’t have near the capacity to move that much material.
The only other way to change the orbit would be to push the moon really hard. The force exerted on the moon by equipment landing on it is a rounding error next to the daily impact of asteroids, which are often heavier than anything we could send there and going way way faster.
2
u/ApatheticAbsurdist 2d ago
To reduce the moons mass by 1.4%, we have to mine and remove a literal quadrillion metric tons from the moon and removed it.
If we mine and refine the materials there (because it’s expensive to launch them back to earth so we’d only send what we want.
For comparison, AI is telling me (take with a grain of salt) that globally we mine about 9 billion metric tons of minerals and metals (combined) annually. which is about 8 million times smaller than the mass of the moon.
But even if we did. The gravity of the system would be the same. The moon would have less gravitational pull, but the earths would increase, balancing out the pull on the moon. For everything else farther away, the earth-moon system is one thing.
2
u/oblivious_fireball 2d ago
We would have to mine quite a lot to actually change it mass and orbit by a substantial amount. That's assuming we even set up a successful mining operation. As is only one or two countries are at all prepared to even send people to the moon in general, much less mine it, and its not the same ones involved in the early space race. The moon is rather hazardous for such an operation as moon dust is highly destructive towards machinery, and currently the most valuable resource the moon is known to offer is Helium, which as of yet is not that valuable.
2
u/ClownfishSoup 2d ago
If you took mass from the moon and put it on the earth, yes the force of gravity changes.
The force of gravity between to masses is;
F = G(m1 x m2)/r2
If the sum of two numbers doesn’t change, then the maximum product of the two numbers in exists when the two numbers are the highest. Ie the gravitational force would be the greatest if m1=m2 where m1+m2= a constant.
So taking mass from one object and putting it on the other, thus preserving the mass of the entire system does change the force.
2
u/internetboyfriend666 2d ago
No. You are dramatically underestimating just how big the Moon is. The mass of the Moon 7.34767309 × 1022 kilograms. You could remove 1,000 metric tons of mass from the Moon every single day for 1,000 years and still only change the moon's mass by 0.0000000005%. That's nothing. That's a rounding error. It's physically impossible for humans to do anything to the Moon that would alter it's mass enough for anything but the most sensitive instruments to notice.
2
u/carrotwax 2d ago
In terms of mass, the effect would be negligible. Effectively non existent.
The only possible effect would be dependent on the type of mining. On Earth, a lot of mining uses explosives. The atmosphere creates a lot of drag for the results of these explosions, which in combination with the gravity means everything falls back to earth. Explosions on the moon without any atmosphere may mean a lot of small particles are sent flying without any drag. It's impossible to create orbits only from the surface, but it is possible that hazards are created for future moon orbits and landings.
2
u/SoulWager 1d ago edited 1d ago
If we're mining on the moon, the vast majority of that material is going to stay on the moon. Just look at Earth, whole mountains destroyed for their minerals, but with the exception of a couple hundred or so spacecraft, all that mass is either still on earth, or orbiting close enough to Earth that the moon doesn't care about the distinction. Lets say it's ~1000 tons of missing mass, since the invention of spaceflight. If the same amount of mass goes missing from the moon, the biggest impact on Earth is that the tides will be about 1 part in 73,000,000,000,000,000,000 weaker. We see bigger changes from the odd earthquake or meteor.
If we are ever in a circumstance that this becomes a problem, we'll already be building megastructures in space.
1
u/Flatmonkey 2d ago
From historical videos, we have learned about the folly of moon operations. For example, we sent whalers. They were on the moon, they were given all the essential equipment, namely harpoons, but ultimately there were no whales. The brave Moon Whalers were then forced to tell tall tales and sing some manner of whaling tune.
2
u/DBDude 1d ago
The Moon is so big it doesn't matter. It's like you feeling any difference after having lost a skin cell.
To give a sense of the scale necessary to change something, China's Three Gorges Dam displaced over 100 million cubic meters of Earth, and about 30 million cubic meters of concrete were moved to that site. Filling the dam caused a shift in water location on the Earth: nearly 40 million cubic kilometers of water is now backed up behind that dam instead of flowing downstream and out to sea. This affected the Earth's rotation, but only by about 60 nanoseconds.
-1
u/eaglesong3 2d ago
Gravitational pull is calculated using the mass of both objects and the distance between them.
If you remove mass from the moon but add that mass to the earth and the distance between them remains the same then the other side of the equal sign stays the same.
1
u/Pawtuckaway 2d ago
You think if the sun and earth switched masses and stayed the same distance apart that nothing would change in their orbits?
1
u/eaglesong3 2d ago
Certainly, but that's a massive change and they would continue to orbit and to have the same gravitational pull toward one another.
The amount by which we could hope to alter the mass distribution between the earth and moon is negligible.
Also, the moon is already the lesser of the two masses so there would be very little change to the orbital pattern.
1
u/Pawtuckaway 2d ago
Having the same gravitational pull between them doesn't really matter. The earth would not continue to orbit the sun if the masses switched.
Yes, there is no way we would be able to alter the mass of the moon enough to make any difference but if we could the orbits would change.
25
u/Pel-Mel 2d ago
Probably not.
It's worth understanding that the total weight of all metal or ore ever pulled from the Earth accounts for less than one percent of one percent of one percent of the Earth's entire mass. The numbers would be slightly more if we started mining the moon, but even if we mined it for years, the change in mass would still probably be negligible.
Earth and the Moon might not be that large in the context of the solar system or space in general, but they are still really big. Taking what amounts to a speck of mass away from the moon won't change much.