How have
scientists discovered the density of the earth?
Unfortunately, this is not a value which can be measured directly
(such as the density of a rock or a potato, for example).
Therefore, we can only use indirect observations.
The overall density of the earth is actually fairly easy to
calculate: if density equals mass divided by volume, and we can
find the mass and volume of the earth, the math is simple. Well,
the volume is easy - we can easily arrive at a radius for the
planet, and get the volume from the equation:
V=4/3 X pi X r3
But how do we get mass? This is a bit tougher, and relates to the
earth's gravitation attraction on various objects: you, me, the
moon, and so forth. We need to use Newton's formula for
gravitation:
G=m1 X m2
/ d2
In this case, G
is the gravitational attraction between any two objects (like the
earth and moon), m1 is the mass of the earth, m2 would be the mass
of the moon, and d is the distance between them. Solve for m1 and
we have the mass of the earth.
Now, plug both values into the equation:
D = m / v |
