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To move or rotate any object, we need some force, this force can interact with object in different ways, contact force(electromagnetic force between atoms), magnetic force etc. All these forces have interaction particles.

It seems that force that make gyroscope precession is non-contact, not existing force, doesnt make sense that object can change location in space without any "interaction particles".

What are "interaction particles" that cause gyroscope precession?

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  • $\begingroup$ interaction particles You don’t need quantum field theory to understand a gyroscope. Classical mechanics works fine for this. $\endgroup$
    – Ghoster
    Commented Nov 22 at 21:18

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Photons and gravitons, not that that provides any meaningful physics insight.

The question is somewhat misguided. For instance:

"To move or rotate any object, we need some force"

Do we? Newton says, "An object in motion stays in motion unless acted upon by an external force". So here we have a moving object with no forces. I feel the same way about rotating.

Re: Exchange Particles. I know popular science communicators love talking about forces being caused by exchanging particle, and show images of (for example) two canoeists throwing a ball and the canoes move away from each other--this always seems to cause more confusion than clarity. People ask, "but how can a force be attractive?" without considering virtual particles can have negative energy...it's all far too literal.

Virtual particles are lines in a diagram representing a term in a perturbation series expansion of an amplitude, that is, there is a force field that mediates the interaction and when we calculate that interaction, it has a coherent series expansion that looks like individual particles. I emphasized "coherent" because it means the intermediate field state isn't "one virtual photon" or "2 photons, one which turns in an $e^+e^-$ pair", and so on. As with the Young's Double Slit Experiment, where the particle goes through both slits, the intermediate field state is all the possible intermediate states, which looks like: a big messy field.

So we tell laymen it's just simple "exchange of force carrying particles", but those are just approximations to a big messy field, so maybe it's better to skip to the ending: forces are carried by big messy field, which is what we all thought in the first place.

And there are 4 fields to choose from: the electromagnetic field, the 2 nuclear forces, and a classical field: gravity.

So EM and gravity make the gyro work, but you already knew that.

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  • $\begingroup$ wheel is not precess until you release one end $\endgroup$
    – 22flower
    Commented Nov 22 at 15:04
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In the process of gyroscopic precession:
For the gyro wheel there is continuous internal relocation of (angular) momentum. That is to say, there are continuous bending forces as some areas of the gyro wheel are being accelerated and others are being decelerated.

There is a case that also has internal relocation of (angular) momentum, but easier to understand. It's a case that is commonly referred to as 'Feynman's wobbling plate'.

When a spinning plate is thrown up in the air the angular momentum of the plate will be constant; constant both in magnitude and direction.

Any wobble of that spinning plate will not go away when the plate is free from the throwing hand; if that plate would be in a vacuum (hence no air friction) then the wobbling will sustain forever. Youtube video by Jacob Forster: Feynman's wobbling plate

The fact that the plate is rigid is an essential element. It is because of that rigidity that the bending forces do not give rise to dissipation of energy. Comparison: making pizza dough stretch by spinning it (giving the dough freedom to stretch by throwing it upward). You never see that spinning pizza dough wobble. That's because the pizza dough is not rigid; any bending force immediately dissipates.


In the case of a gyroscope:
A necessary condition for gyroscopic precession to occur is that the gyro wheel is rigid. It has to be rigid because in order to display gyroscopic precession the gyro wheel has to support internal relocation of momentum.


There is a 2012 answer by me in which I describe the mechanism of gyroscopic precession. That description explains why it is that when a spinning gyroscope is released it doesn't flip down, but instead settles to gyroscopic precession.

In that description I do not use the abstract concept of spin angular momentum. Instead the explanation capitalizes on symmetry.

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  • $\begingroup$ I look at this explanation but dont understand why is this internal strut forces relevant, I see only two external forces ; gravity and normal force at pivot, that want to flip wheel down. youtube.com/watch?v=YiQVna7UTiQ $\endgroup$
    – 22flower
    Commented Nov 22 at 18:41
  • $\begingroup$ @22flower About that particular youtube video: the author of that video is describing the gyroscopic precession in terms of the particular implementation that he is using. I think that is not a good approach: in my opinion explanation should be generic. I was previously aware of that youtube channel: 'Physics Unsimplified'. The two videos there about the Dzhanibekov effect are very good. This one, the one about gyroscopic precession, is unfortunatly hardly helpful, if at all. $\endgroup$
    – Cleonis
    Commented Nov 22 at 20:00
  • $\begingroup$ I find this video pretty intuitive: youtube.com/watch?v=jQEKhIovKA0 But still dont understand how Walter rotate itself, because I dont see any external force which will do this rotation, you cant move/rotate object with internal forces because they always cancel each out. : youtube.com/shorts/KhPTVgkMXQ8 To me gyro seems as "reactionless propulsion" even I know this not exist.. $\endgroup$
    – 22flower
    Commented Nov 22 at 23:14
  • $\begingroup$ @22flower I can see how Matthias Wandel is tempted to follow that line of thought, but orbital mechanics and gyroscopic precession mechanics are distinct cases. The kind of comparison that Matthias Wandel makes in that video is not valid. If you would have a fleet of satellites, initially all orbiting in the same plane, and you would use thrusters to move that fleet to another inclination, then during that transition the fleet is not all orbiting in the same plane; there will be some deviation. By contrast: a gyro wheel, being rigid: all parts remain in the same plane relative to each other $\endgroup$
    – Cleonis
    Commented Nov 22 at 23:43
  • $\begingroup$ @22flower About that video short with Walter Lewin. Walter changes the orientation of the spin axis of the bicycle wheel from perpendicular to his own (vertical) axis, towards alignment with his own (vertical) axis. The ensuing effect is the same effect as that is used when a balancing robot is kept upright with reaction wheels In the case of those reaction wheels there is variable rotation rate of the reaction wheels. Walter uses variable orientation of the bicycle wheel to regulate. The closer the axes alignment, the larger the effect. $\endgroup$
    – Cleonis
    Commented Nov 22 at 23:59
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The pair of forces that cause precession in a gyroscope or a spinning top are the normal force at the pivot and gravity, which together create a couple on the gyroscope. I don't know what you would call the "interaction particle" for gravity, but I don't see anything mysterious about precession.

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  • $\begingroup$ If you never seen spinning wheel on rope, you will know if you release one end that will not flip down and start to precess? $\endgroup$
    – 22flower
    Commented Nov 22 at 15:01
  • $\begingroup$ @22flower There is still nothing mysterious about this. Two forces create a couple which, when acting on a spinning object, causes precession. $\endgroup$
    – gandalf61
    Commented Nov 22 at 15:36

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