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irfangreen1 · May 7, 2012, 06:15 AM

What's the mass of the earth? Amd how can we measure it?

ebaines · May 7, 2012, 06:27 AM

Originally Posted by irfangreen1

What's the mass of the earth? Amd how can we measure it?

For mass of the earth see: http://en.wikipedia.org/wiki/Earth_mass

One way to derive this is to start with Newton's Law of Gravitation for an object of mass m subjected to earth's gravity:

$<br /> F= \frac {GMm} {R^2}<br />$

where 'M' is the mass of the earth and R is the radius of the earth. This force can also be expressed as:

$<br /> F = mg<br />$

Set these two equations equal to each other and solve for M. Of course this assumes that you have values for the gravitational constant 'G,' the radius of the earth 'R,' and acceleration due to gravity at the earth's surface 'g.'