Originally posted by Boxing Pythagoras
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So how does it work? The elegant answer is that the pendulum swings in a fixed plane and the Earth rotates beneath it, but this explanation is misleading. At the north or south pole, the pendulum is moving in a fixed plane (if we disregard the fact that the Earth is also revolving through space)
In order for a pendulum experiment to be accurate, precautions must be made to assure that the pendulum is not acted upon by any outside forces other than gravity. For example, to start the pendulum moving, it is usually held at an angle by a string, which the experimenter then burns to release the pendulum. Letting the pendulum go from one's hands, or even cutting the string, could give the pendulum undesired momentum in a particular direction. A heavy pendulum on a long, rigid wire can continue oscillating for long periods of time, but eventually air resistance will cause the motion to lessen and stop. Museums will often use an electromagnetic drive to keep their pendula moving, because such a setup provides additional energy to the pendulum without affecting its direction of motion. http://www.brown.edu/Departments/Ita.../pendulum.html
It is worthwhile correcting a common misunderstanding about Foucault's Pendulum. It is sometimes said (perhaps poetically) that the pendulum swings in a plane fixed with respect to the distant stars while the Earth rotates beneath it. This is true at the poles. (It is also true for a pendulum swinging East-West at the equator.) At all other latitudes, however, it is not true. At all other latitudes, the plane of the pendulum's motion rotates with respect to an inertial frame.
It is easy to deal with this misunderstanding. Consider a pendulum at the equator, swinging in a North South plane. It's obvious from symmetry that the plane of this pendulum doesn't rotate with respect to the earth and that, relative to an inertial frame, it rotates once every 24 hours.
It is easy to deal with this misunderstanding. Consider a pendulum at the equator, swinging in a North South plane. It's obvious from symmetry that the plane of this pendulum doesn't rotate with respect to the earth and that, relative to an inertial frame, it rotates once every 24 hours.
. . . the pendulum swings in a plane fixed with respect to the distant stars while the Earth rotates beneath it. This is true at the poles.
Evidently the Helio model requires some very eclectic thinking for the FP to be evidence for the moving earth. Apparently the fixed plane is fixed relative to some stars and not others. Apparently for the FP to work as desired by the Helios,
1. the moving stars within the galaxy become fixed, yet the Helio model requires that they always move,
2. the plane of inertia at the poles is also fixed, thereby ignoring the motion of the earth around the sun, moon and galaxy.
Even so, for the FP to be evidence of the Helio model, the FP assumes all other bodies are either fixed, or irrelevant and all other forces other than gravity (except the engine) do not act on the FP.
Wow!! Now that is some eclectic proof for something the Helios already know is true - the moving earth, that according to the FP only spins once per day.
The FP is standard Helio gibberish, which makes physics into a laughing stock.
JM
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