Leaves have formed the circumference of the circle

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    Circle Circumference
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Discussion Overview

The discussion revolves around the phenomenon of leaves appearing to revolve in a circular motion around a point on the ground, prompted by observations of air currents. Participants explore the underlying mechanisms that could explain this behavior, touching on concepts from fluid dynamics and meteorology.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant observes that leaves and dust particles seem to form a circle and questions the nature of the air currents responsible for this effect.
  • Another participant notes that circular air currents are common, referencing larger phenomena such as typhoons and hurricanes as examples.
  • A different participant introduces the concept of turbulence, explaining that air flowing past obstacles can create eddies and circular motions, which may contribute to the observed behavior of the leaves.
  • One participant discusses the balance of forces at play, mentioning a centrifugal effect that pushes leaves outward and a ground air current that pulls them inward, suggesting that these forces reach equilibrium at a certain radius. They reference the Tea Leaf Paradox to explain the ground current's role.

Areas of Agreement / Disagreement

Participants present multiple perspectives on the phenomenon, with no consensus reached on a single explanation. Various mechanisms are proposed, indicating a range of competing views.

Contextual Notes

The discussion includes assumptions about the nature of air currents and the behavior of leaves in a fluid medium, but these assumptions are not fully explored or defined. The relationship between the centrifugal effect and the ground air current remains unresolved.

aayushmittal
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Sometime in the afternoon or in evening i see some leaves caught in something like air current which i feel that there some thing more. The leaves (tiny fallen leaves and some dust particles) revolve around a center. It looks like the leaves have formed the circumference of the circle and they are revolving around some point on the ground. Please tell me why this happens. This cannot just be any air current. The circle is horizontal not vertical.
 
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It is quite common for air to have approximately circular currents. Typhoons and hurricanes, and cyclones in general, are the same thing on a much larger scale.
 
Look up "turbulence".

When air flows past a corner, for example, some of the flow will curl around creating eddies. You can also get different angled breezes adding up to some circular motion and groups of objects can funnel a breeze into a vortex. As long as there is a breeze, these motions can be sustained for quite a time.
 
There are two effects balancing each other out. There is centrifugal effect forcing the leaves apart, and there is a ground air current pulling the leaves towards the center. At a certain radius, these two effects balance out. The reason for the ground current towards the center is explained by the Tea Leaf Paradox. Note that in a fluid, leaves are near-buoyant, so centrifugal effect is relatively insignificant.
 

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