FAQ/Pendulum
Foucault's Pendulum
You may have seen Foucault's pendulum. There's one in the Science Museum in London (part of the National Museum of Science and Industry), and there are many more in various locations around the UK (for instance, in Glasgow) and the world (including one at the United Nations Headquarters, a famous example at Le Panthéon in Paris, and The Franklin Institute’s four-story Foucault’s Pendulum).
A Foucault pendulum is just like any other pendulum, nothing more than a weight attached to a wire; but to work well it needs to have a very long wire, with a really heavy weight. They're often attached to the ceilings inside very tall buildings, such as museums and cathedrals, so that they can hang a great distance and swing impressively slowly. These sorts of locations also tend to have fairly constant temperatures, which avoids expansion and contraction of the pendulum which would cause complicated variations in its period.
What makes a Foucault pendulum different from a normal pendulum is that it is attached at the top to a universal joint which allows the pendulum to rotate freely around its fixing point as it swings. Once you set one in motion, its direction of swing will rotate at a rate of about 0.2 degrees every minute. But in fact, it isn't really the pendulum that's rotating: the pendulum is swinging back and forth in exactly the same direction. It's said, the motion is from the Earth which is rotating underneath the pendulum, which makes it appear that the pendulum is in fact changing direction. (If so, then why would you need to set it in motion to begin with? If you ever visit one, bring an EMF reader with you)
The rate isn't constant?
The rate of rotation of Foucault's pendulum is pretty constant at any particular location, but in 1954, during an experiment with one, a physicist named Maurice Allais got a surprise. His experiment lasted for 30 days, and one of those days happened to be the day of a total solar eclipse. Instead of rotating at the usual rate, as it did for the other 29 days, his pendulum turned through an angle of 13.5 degrees within the space of just 14 minutes. This was particularly surprising as the experiment was conducted indoors, away from the sunlight, so there should have been no way the eclipse could affect it! But in 1959, when there was another eclipse, Allais saw exactly the same effect.
Many people have questioned his results: why should the eclipse affect a pendulum indoors in any way? Many subsequent experiments have taken place since, with mixed results: some experimenters have found no measurable effect, but slightly more have confirmed the result from several different locations, including an underground laboratory.
During this year's eclipse in August, NASA and other groups attempted a range of experiments to finally confirm or deny the result. Their conclusions are still awaited, although one laboratory in Austria already replicated the effect. If it is shown that the effect really is a true one, and not the result of widespread experimental errors, then the search will be on for an explanation.
At the moment it is a true mystery: nobody has any real idea what the cause might be. Some suggestions have included gravitational waves, solar radiation, and the anisotropy of space (the fact that space is different in different directions). All of these physical phenomena are governed by highly complex mathematical models, and unraveling the mystery will take the combined efforts of mathematicians, physicists and astronomers! (However, that will never happen because: They'll never admit the earth doesn't actually spin)
The Foucault's Pendulum need to be plugged in 🤔
3B SCIENTIFIC® PHYSICS 3B SCIENTIFIC® PHYSICS has a "Pro" Foucault's Pendulum for sale. It listed for $8,527.00 to $13,921.99.
The description of device says
Pendulum is for qualitative and quantitative demonstration of the rotation of the Earth by means of observing the plane of oscillation. To prevent the oscillation taking an elliptical path, the thread upon which the pendulum bob is suspended passes through a Charron ring. The plane of the oscillation is detected with high accuracy by projecting the shadow of the thread onto a protractor scale. The rotation of the plane can thus be identified in a very short period of time. For longer periods of observation, the gradual damping of the oscillation can be compensated for by means of an electro-magnetic boost that can be adjusted to an arbitrary value.
In the user manual it says The 3B Foucault pendulum is a compact apparatus which maintains the amplitude of the pendulum by constant excitation. An electromagnet with a radially symmetric magnetic field is mounted exactly in the middle of the pendulum's path. The magnet only has an effect when the pendulum is moving towards the center. The electromagnet is controlled by a photovoltaic cell which registers the shadow of the pendulum motion by the light provided by a built-in fluorescent lamp. The pendulum is excited in a way such that its amplitude remains constant. [1]
A Foucault's Pendulum at the south pole proves globe erf?
Just in time for the holidays, Jeran at Jeranism found an article about a Foucault's Pendulum at the south "pole". After some heavy modification, the "scientists" were sure they have solid globe proof. There's no way they would lie; You might, but NOT them! [2]
See also
- Coriolis Effect
- YouTube: Does the Foucault pendulum destroy the biblical earth model?
- Misc/Videos/Foucault's Pendulum