Sunday, May 2, 2010

How do you weigh a planet?
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1 comment:

  1. MarkleMay 5, 2010 at 7:18 AM

    The attractive force of gravity between two objects has the equation:

    F_g = G * M * m / r ^ 2

    G and r can be, and have been, determined experimentally. So if you take a known mass m, and you measure F_g (with a spring scale, for instance), you can solve for M. That's how we can get the mass of the Earth.

    Weighing other planets involves looking at how they interact with their moons and with other planets gravitationally, using much more complicated equations. Happily, computer simulations have made this process somewhat streamlined.

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