A flip of the Earth on its axis

  • Context: High School 
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Discussion Overview

The discussion revolves around the concept of whether the Earth can flip on its axis, exploring both theoretical and experimental perspectives. Participants examine the implications of Earth's rotation, its stability, and the physical models used to simulate such behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants assert that the Earth does not flip on its axis, citing the stability of its rotational axis and the influence of gravitational forces.
  • One participant describes a model using a pool cue ball to demonstrate flipping behavior, raising questions about its relevance to Earth's dynamics.
  • Others argue that the Earth's axis is stable due to its equatorial bulge and the conservation of angular momentum, suggesting that flipping would require significant energy changes.
  • Concerns are raised about the accuracy of a video that depicts the Earth flipping, with participants pointing out potential errors in how angular momentum is represented.
  • There is discussion about the definition of "flipping" in the context of a partially liquid body like Earth, questioning what conditions would constitute a flip.

Areas of Agreement / Disagreement

Participants generally disagree on the possibility of the Earth flipping on its axis, with multiple competing views presented regarding the stability of Earth's rotation and the implications of the models discussed.

Contextual Notes

Limitations include the dependence on the definitions of flipping and the assumptions made about the Earth's structure and behavior as a non-rigid body. The discussion also highlights unresolved questions about the energy required for such a flip and the implications of continental drift.

Who May Find This Useful

This discussion may be of interest to those studying physics, particularly in the areas of rotational dynamics, celestial mechanics, and the behavior of non-rigid bodies.

  • #31
Thanks for the info!
 
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  • #32
arydberg said:
Also on the subject of table tennis balls if you weight one half of the ball. by spliting it in two, filling one half with epoxy and glueing it back together and color the weighted half it sits with the weighted half down but when spun it will flip. It is stable when spinning only with the weighted half on top. You can also drill a hole in the ball, half fill it with water. and freeze it and color the weighted half. It workes fine for a short time till the water melts.
What is the spin axis with respect to the halves?

The half filled balls give you no clear intermediate axis. And your center of mass is not the ball center, so you have substantial external torques around the CoM from the air cushion support. This is likely quite different from the typical intermediate axis flipping.
 
  • #33
In order to get the most intriguing demo, is it better to have the three principal MoIs fairly close to each other, or is it better if they are as different as possible?
 

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