Foucault pendulum and a round globe

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Discussion Overview

The discussion revolves around the use of Foucault pendulums to demonstrate the Earth's rotation and shape. Participants explore whether multiple pendulums placed at various latitudes and longitudes could provide evidence for the Earth being a sphere, considering the implications of gravity and observational limitations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the angle of precession of Foucault pendulums, which depends on latitude, could be used to demonstrate the Earth's rotation.
  • There is a proposal that placing several Foucault pendulums at equidistant points could help prove the Earth is a sphere, potentially excluding other shapes based on smoothness assumptions.
  • One participant emphasizes the need for pendulums to be spaced densely rather than at the same altitude to ensure smoothness in the data collected.
  • Another participant raises the idea that a model of gravity might imply an equipotential surface, which could suggest a spherical Earth without needing to observe pendulum behavior.
  • A counterpoint is made regarding the simplicity of observing celestial bodies, such as the North Star, to infer the Earth's shape, although a flaw is noted about the North Star's historical position.
  • One participant speculates that if the sky were cloudy, the Foucault pendulums would still indicate rotation, but questions arise about the transition to a heliocentric model without other observational evidence.

Areas of Agreement / Disagreement

Participants express various viewpoints on the effectiveness of Foucault pendulums in proving the Earth's shape and rotation, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

There are assumptions regarding the smoothness of the Earth's surface and the model of gravity that are not fully explored. The discussion also highlights limitations in observational methods, particularly in historical contexts.

xaratustra
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Imagine we are all cavemen without satellite technology and just discovered the Foucault pendulum! As we know the angle of presession depends on the latitude. This can be used to prove that the Earth is rotating, right? Now by putting several Foucault pendula around the Earth, at equidistant longitude and latitude, can we prove that the Earth is a sphere as well?
 
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xaratustra said:
Now by putting several Foucault pendula around the Earth, at equidistant longitude and latitude, can we prove that the Earth is a sphere as well?
You could exclude a lot of potential shapes, and by assuming certain smoothness between your sample positions narrow it down to a sphere.
 
cool. then all pendula must be installed at the same altitude to guarantee smoothness. :smile:
 
xaratustra said:
cool. then all pendula must be installed at the same altitude to guarantee smoothness. :smile:
It's not about the altitude, but how densely they are spaced.

Also, since pendulums are based on gravity, you have to assume some model of gravity, which by itself might already imply an equipotential surface, without even the need for swinging pendulums.
 
Last edited:
xaratustra said:
Imagine we are all cavemen without satellite technology and just discovered the Foucault pendulum! As we know the angle of presession depends on the latitude. This can be used to prove that the Earth is rotating, right? Now by putting several Foucault pendula around the Earth, at equidistant longitude and latitude, can we prove that the Earth is a sphere as well?

Wouldn't it be much easier for them to just glance at the sky and notice how the position of the North Star varies with latitude?
(Flaw: The North Star moves, it was not north in all periods of history.)
 
If it was (very) cloudy all over the Earth, it would be harder to arrive at an initial Geocentric model Universe but the Fuocault pendulums would definitely indicate rotation. No one would every have moved to a Heliocentric model, I reckon ('till Radio came along).
 

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