Description:
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"Gravity produces a torque perpendicular to both
the axis of the gyroscope and the vertical, and thus causes the horizontal
precession. On a less abstract level, the precession can be explained
in terms of the downward pull of gravity that tries to make the wheel
rotate faster at the bottom than at the top. Since the wheel is rigid,
this can happen only if the wheel moves horizontally in the direction
in which the bottom of the wheel is spinning. The earth is a large gyroscope
that precesses once every 26,000 years due to the gravitational torque
exerted by the sun on the slight bulge at the equator. Note that the precessional
frequency is inversely proportional to the frequency at which the gyroscope
is spinning. This fact can be illustrated by observing carefully the precession
as the gyroscope slows down. Furthermore, the precession frequency is
independent of the angle that the axis makes with the horizontal. The
torque is greatest when the axis is horizontal, but so also is the distance
it has to move to precess once around, and the effects just cancel."
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