What causes the feather movement at 2:56 in the documentary?

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A small movement of the external part of the feathers can be appreciated In minute 2:56 of this documentary: .

What could be the cause? Perhaps the residual atmosphere?
 
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I would say any movement on the feathers would be due to residual vibrations from the release mechanism. When the feathers are hanging, you have internal forces inside them that hold the different parts up. Once released, it takes some time for these forces to relax, leaving minor oscillations in the feathers. That being said, there are hardly any movements at all.

Awesome video though.
 
After the feather is released, an upwards motion can be observed in the upper, external sides. Might be due to transmitted vibrations, but looks very similar to air resistance...
 
Gravity pulls down on all parts of the feather, making the edges droop. Release the feather in a vacuum and the stresses become zero. Plus it takes some time for the ends of the feather to become unstressed. That is what you see in a vacuum.
Imagine hooking a mass to a spring and hanging it. The spring will be extended. Release the spring and there will be a time lag before the mass begins moving, and only when all of the spring has become un-extended.
 
256bits said:
Gravity pulls down on all parts of the feather, making the edges droop. Release the feather in a vacuum and the stresses become zero. Plus it takes some time for the ends of the feather to become unstressed. That is what you see in a vacuum.
Imagine hooking a mass to a spring and hanging it. The spring will be extended. Release the spring and there will be a time lag before the mass begins moving, and only when all of the spring has become un-extended.

Exactly... A friend was telling me, just now, precisely that solution, and I was visualizing it with the mass and the spring...

Thanks...