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How possible is it to turn the Magnetosphere and our moon into a generator?

Lets say we have all the materials and labor needed to perform the construction and that we have the delivery method for returning the energy. Can we build a giant stator by using the Earth's Magnetosphere as the magnet and copper coils built on our moon? As the moon orbits would it produce a charge in the coils?

Additionally, if this is possible, do you see any issues scaling this up to use multiple planets and the Sun or our Galactic Center and multiple solar systems?

Thank you for entertaining this thought.

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  • $\begingroup$ 3 things: first Moon is really very far, second magnetic field obey inverse square law and third perpetual machine don't exist! bonus fourth for new member: the two are tidal lock ;D $\endgroup$
    – user6760
    Commented Jan 17, 2022 at 1:42
  • $\begingroup$ I thought magnetic flux would travel forever if nothing effected it? I need to research inverse square law thank you for that. I never said this would be able to go on forever, nor did I say this wouldn't effect the orbits . Lastly, The orbit being tidal locked wouldn't matter as so are the coils of a stator. $\endgroup$
    – Alkimus
    Commented Jan 17, 2022 at 2:20
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    $\begingroup$ @user6760 its worse than that... the field strength in the far field of a magnetic dipole (and the moon is very much in the Earth's far field) follows an inverse cube law. $\endgroup$
    – Starfish Prime
    Commented Jan 17, 2022 at 12:18

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Yes... and no...

  • The Earth rotates (once per 24 hours) faster than the moon orbits (once every 27.3 days). From this perspective, it's the moon that's the stator and the Earth that's the rotor.

  • The Earth's magnetic field was measured as part of several Apollo missions to the moon. The article uses the unit of Gammas. One gamma = one nano-Tesla. So the Earth's field strength on the moon is approximately 31 micro-Teslas.

Here's the bad news...

  • The rotor in an average industrial generator turns at about 150,000 times per minute. Since the Moon orbits once a month (more or less) and the Earth rotates once a day (more or less), then we'll simplify this and say that the Moon is just standing still and that magnetic field rotates through the stator once a day. Now, this technically doesn't stop you. It just means you need at least 216,000,000X more windings to achieve the same result. Remember, that's a multiplier. The windings in an industrial generator can literally be miles and miles long... so we're talking hundreds of millions to billions of miles of copper windings. And it gets worse...

  • The magnetic field strength of industrial geneators is measured in Teslas. Not micro-Teslas. Technically, this also doesn't stop you. You just need at least 32,000X more coil.

Our final multiplier (multiplier...) is 216,000,000 * 32,000 ~= 7 trillion.

Trillions of miles of copper wire....

There probably isn't enough copper in the planet Earth to build the coils you'd need to do what you want. But I could be wrong about that. Still, a bit impractical.

Don't let that stop you!!!

The fun thing about science fiction is that the word "fiction" is involved. If you only stick with science-fact, all you're writing is a documentary. What do I suggest?

That you use a material, let's call it worldbuildingidium, that's a billion times more likely to move an electron than copper. Now you only need big mother-hubbard geneartors and you're not depleting Earth's supply of copper to build a second moon just to run one factory. Food for thought.

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    $\begingroup$ Thank you for your answer. I have been thinking about it and have come up with a solution to the issues you pointed out. Just focused on the planet and not looking into the star, due to distance. I believe satellites would be the answer. $\endgroup$
    – Alkimus
    Commented Feb 19, 2022 at 9:03
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Yes, but you wouldn't generate much power.

You can see on earth the magnetic field of the earth is just barely enough to move a small piece of metal in a compass. On the moon, the magnetic field is even weaker because it needs to cover such a vast area.

You can tap the magnetism of the sun.

The sun produces solar flares and Coronal mass ejections. These produce a massive amount of power, enough to burn out grids on earth, and a theoretical machine on the moon could collect this magnetic power.

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    $\begingroup$ I like this alternative! You'd have to have substantial storage since CMEs don't happen regularly, but it's a pretty good idea the falls well with suspension-of-disbelief. Better still, CME's push all kinds of energy, not just magnetic, and all that could be captured. $\endgroup$
    – JBH
    Commented Jan 17, 2022 at 17:43

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