[lepton]

“What is the mass of all of the buildings, structures, vehicles, digital watches, and road surfaces, man has made on the earth so far?”

They have not changed the mass of the earth. The materials were already part of the earth.

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That’s not the point. The point is that I don’t think you understand how miniscule our total building efforts are to the mass of the moon - such that many multiples of human efforts would still be a trivial amount compared to the mass of the moon.

[Wuli]

It is not trivial because (1) the mass of the moon is trivial compared to the mass of the earth, yet (2) in spite of that the impact of the moon on many aspects of the earth is quite major. Before extracting ANYTHING from the moon and delivering it to the earth in massive amounts over many years, the scientists need to, and can. calculate how much can be extracted before the present earth-moon balance is changed.

There is another option they can do. The ships sent to retrieve material from the moon can not be sent to the moon empty, but carrying tonage that will be left on the moon equal in weight to what they will remove. THEN nothing will change.