[ARPAN]

Foucault’s pendulum
Earlier, I spoke as if a frame of reference attached to the surface of the
rotating earth was just as good as any other frame of reference. Now,
with the more exact formulation of the principle of inertia, we can see
that that isn’t quite true. A point on the earth’s surface moves in a circle,
whereas the principle of inertia refers only to motion in a straight line.
However, the curve of the motion is so gentle that under ordinary condi-
tions we don’t notice that the local dirt’s frame of reference isn’t quite in-
ertial. The first demonstration of the noninertial nature of the earth-fixed
́
frame of reference was by Leon Foucault using a very massive pendu-
lum (figure n) whose oscillations would persist for many hours without
becoming imperceptible. Although Foucault did his demonstration in
Paris, it’s easier to imagine what would happen at the north pole: the
pendulum would keep swinging in the same plane, but the earth would
spin underneath it once every 24 hours. To someone standing in the
snow, it would appear that the pendulum’s plane of motion was twisting.
The effect at latitudes less than 90 degrees turns out to be slower, but
otherwise similar. The Foucault pendulum was the first definitive experi-
mental proof that the earth really did spin on its axis, although scientists
had been convinced of its rotation for a century based on more indirect
evidence about the structure of the solar system.


which is then correct i.e. does earth rotate about its own axis and if it does then what is wrong with Foucault’s pendulum