Spinning Shit

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Masato
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Spinning Shit

Postby Masato » Mon Aug 03, 2020 8:45 pm



Pretty cool/crazy/fascinating

Makes me think of stories of the earth's poles shifting...? They address it at the end, somehow saying that won't happen with Earth but I didn't quite follow the explanation :oops:

The vid also gives me a bit more faith in the authenticity of those space station videos, lol

[spoiler]
Spinning objects have strange instabilities known as The Dzhanibekov Effect or Tennis Racket Theorem - this video offers an intuitive explanation.

References:
Prof. Terry Tao's Math Overflow Explanation: https://ve42.co/Tao

The Twisting Tennis Racket
Ashbaugh, M.S., Chicone, C.C. & Cushman, R.H. J Dyn Diff Equat (1991) 3: 67. https://doi.org/10.1007/BF01049489

Janibekov’s effect and the laws of mechanics
Petrov, A.G. & Volodin, S.E. Dokl. Phys. (2013) 58: 349. https://doi.org/10.1134/S102833581308...

Tumbling Asteroids
Prave et al. https://doi.org/10.1016/j.icarus.2004...

The Exact Computation of the Free Rigid Body Motion and Its Use in Splitting Methods
SIAM J. Sci. Comput., 30(4), 2084–2112
E. Celledoni, F. Fassò, N. Säfström, and A. Zanna
https://doi.org/10.1137/070704393

Animations by Iván Tello and Isaac Frame

Special thanks to people who discussed this video with me:
Astronaut Don Pettit
Henry Reich of MinutePhysics
Grant Sanderson of 3blue1brown
Vert Dider (Russian YouTube channel)

Below is a further discussion by Henry Reich that I think helps summarize why axes 1 and 3 are generally stable while axis 2 is not:

In general, you might imagine that because the object can rotate in a bunch of different directions, the components of energy and momentum could be free to change while keeping the total momentum constant.

However, in the case of axis 1, the kinetic energy is the highest possible for a given angular momentum, and in the case of axis 3, the kinetic energy is the lowest possible for a given angular momentum (which can be easily shown from conservation of energy and momentum equations, and is also fairly intuitive from the fact that kinetic energy is proportional to velocity squared, while momentum is proportional to velocity - so in the case of axis 1, the smaller masses will have to be spinning faster for a given momentum, and will thus have more energy, and vice versa for axis 3 where all the masses are spinning: the energy will be lowest). In fact, this is a strict inequality - if the energy is highest possible, there are no other possible combinations of momenta other than L2=L3=0, and vice versa for if the energy is the lowest possible.

Because of this, in the case of axis 1 the energy is so high that there simply aren't any other possible combinations of angular momentum components L1, L2 and L3 - the object would have to lose energy in order to spin differently. And in the case of axis 3, the energy is so low that there likewise is no way for the object to be rotating other than purely around axis 3 - it would have to gain energy. However, there's no such constraint for axis 2, since the energy is somewhere in between the min and max possible. This, together with the centrifugal effects, means that the components of momentum DO change.

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Postby Masato » Mon Aug 03, 2020 8:46 pm


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Postby Masato » Mon Aug 03, 2020 9:07 pm

This is now a Nick Diaz thread


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Postby Luigi » Mon Aug 03, 2020 9:55 pm

So its saying mountains n shit are like the antenas and disipate force? Why didnt that happen with Mr. Soviet's clay lump?
Image

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Postby Masato » Mon Aug 03, 2020 11:31 pm

Luigi wrote:So its saying mountains n shit are like the antenas and disipate force? Why didnt that happen with Mr. Soviet's clay lump?


wow you actually watched it! lol :D

I was thinking if any of this was part of the function of the pyramids, perhaps the pyramids were built to stabilize the flip? They are on a key latitude, 30 I think, I remember lots of pyramid freaks saying that the LOCATION of the pyramid is not coincidence, but built into the mathematics. Maybe building something like that at the right angle of spin etc would stabilize the spin? To create a controlled 'moment of inertia'?

I don't know I'm just speculating off the vid. I think there was more to pyramids than just that, but it would be cool if any of this was involved

Maybe the clay lump doesn't do that because there are no clear points through which to dissipate the force efficiently, it's all bumpy. But a pyramid etc might be a conduit for that force and tell the object which way it should spin, flip, or not flip.

Or am I totally misunderstanding the concepts? lol

Anyways, so weird to see it flip like that.

Did you understand the part at the end where he nervously reassures us that the earth won't flip like this? Why exactly?

I need to watch it again. Super trippy stuff.

I wonder what he would say about centrifugal force from the spin of the earth, and how he might explain gravity

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Postby Masato » Mon Aug 03, 2020 11:33 pm

We should get back on topic:

Here's a short documentary on Nick Diaz before he came to UFC:


Here is the fight it was hyping:


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Postby Masato » Mon Aug 03, 2020 11:51 pm

Here's some more weird spinning shit:



Explanation of gyro precession: http://bit.ly/U4e8HQ
More: http://bit.ly/GyroMORE
Less Than: http://bit.ly/GyroLESS
Equal To: http://bit.ly/GyroEQUAL

I used to play with a gyroscope as a kid, we did the same thing you could get it to balance sideways on the edge of a table etc. As long as the wheel was spinning fast enough it would defy gravity

challenge @ 5minutes ^^

Will the scale read more, less, or equal than the combined weight before spinning??


wtf they don't give the results to the test? I wanna know!!

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Postby Edge Guerrero » Tue Aug 04, 2020 12:47 am

Masato wrote:We should get back on topic:

Here's a short documentary on Nick Diaz before he came to UFC:


Here is the fight it was hyping:



- People say the Diaz are dumb. But neither of them did stupid tattoos! :lol:
- I rent this space for advertising

Don't be selfish, preserve this world for the next generations.

I'll never long for what might have been
Regret won't waste my life again
I won't look back I'll fight to remain


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