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Re: What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

by BrowserUk (Pope)
on Nov 01, 2015 at 17:55 UTC ( #1146627=note: print w/replies, xml ) Need Help??


in reply to What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

Given the Moon's mass is 7.34771022; and a "cable" made of carbon nanotubes with a tensile strength of 63 gigapascals would need to have a diameter of 4000km in order to endure the tension of that mass -- and that's ignoring the mass of the cable itself ~185 trillion tonnes -- I'll wait until someone works out how to manufacture the 4000km diameter x 400000km cable and finds a source of energy on earth sufficient to lift it into space before I start worrying about the consequences of doing this :)


With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
In the absence of evidence, opinion is indistinguishable from prejudice.
  • Comment on Re: What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

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Re^2: What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?
by salva (Abbot) on Nov 01, 2015 at 20:30 UTC
    The problem is not holding up the moon but stopping it... well, I mean, the main problem!
      The problem is not holding up the moon but stopping it...

      "Tension" is holding it back; not holding it up.

      Actually you'd have to speed the moon up (or slow the Earth down) since the former rotates every 27 days but the latter rotates once a day.

      And if you sped the moon up to match the Earth's rotational speed, then the tension on the cable would be hugely increased necessitating a further increase in its diameter.


      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
      In the absence of evidence, opinion is indistinguishable from prejudice.

      Yes. Once we get the moon to be stable above one point of the earth, there would be (nearly) no force on the rope, and we might get the effect of a Space Elevator.

      But the difficulty would be to get the moon into a suitable position, so it could serve as a counterwight.

      This would probably lead to a lot of changes on earth, e.g related to the tides. Or to Astrology. But I'd like to focus on the opportunities, e.g rope-climbing-competitions ;-)

        The geostationary distance is the same for all bodies at 36000 km (IIRC).

        Are you aware about the tide caused by a moon at that distance?

        Giant amounts of water alone would swap to the "moon side" of the world, not talking about earth quakes and volcanoes erupting.

        Cheers Rolf
        (addicted to the Perl Programming Language and ☆☆☆☆ :)
        Je suis Charlie!

        update

        If I'm not wrong moon's gravitational impact at only 10% of it's normal distance would be 100 times stronger than now. That's not even a Bruce Willis movie anymore.

Re^2: What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?
by Anonymous Monk on Nov 02, 2015 at 09:26 UTC

    The Moon and the Earth are already roped together—gravitationally. And we know what that means.

    I gather the question is if another, physical tether were attached to both. It'd most likely have a healthy amount of slack to account for the elliptical orbit. Perhaps a counterweight is in order at some intermediate point to provide tension. In any case, the rope would have to endure its own weight only (which is still quite a task!), plus some for doing useful work.

Re^2: What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?
by Anonymous Monk on Nov 04, 2015 at 14:31 UTC
    Mass and force are not the same. F = m * a Isaac Newton
      Mass and force are not the same. F = m * a

      No shit Sherlock!

      So, what are you saying? You think there is no acceleration involved?


      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
      In the absence of evidence, opinion is indistinguishable from prejudice.

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