clipped from: www.solstation.com
NASA -- Larger image
Gravitational bumpiness exaggerated.
While Earth is a fairly uniform sphere,
its gravitational field does vary by small
fractions of a percent from place to place.
Not only is the planet bumpy as the result
of slow geological processes such as
tectonic plate movements or polar ice cap
changes, but these processes also create
mass density variations that affect the
local gravitational field
(more from
NASA
and
Astronomy
Picture of the Day).