How fast can a particle rotate?

[emergentsystem]

Without moving in any direction, what is the maximum speed at which a particle can rotate? Does it depend on its mass or size?

Is there a maximum speed of rotation analogous to or dependent on the speed of light? If so, are there any odd temporal effects from the perspective of the particle as it approaches that speed?

 

[Drakkith]

First, I think it's important to understand that fundamental particles are considered to be point-like, meaning they have no size. As such, I'm not sure if the term "rotation" can be applied to them. (Perhaps their wavefunction can be rotated?) Composite particles and larger objects are limited by the strength of their bonds versus the centrifugal force of the rotation. And no object can be rotated so fast that any part of it meets or exceeds the speed of light.

 

[emergentsystem]

Is the "spin" property of particles related to rotation?

And is there a way to calculate the maximum rotation speed for composite particles?

 

[Drakkith]

Is the "spin" property of particles related to rotation?

Quantum spin? No. Quantum spin is a fundamental property of particles. It is "as if" the particle is spinning around on its axis, but it is not. If it were actually spinning, it would have to spin faster than the speed of light in order to generate the magnetic field of the measured stength.

And is there a way to calculate the maximum rotation speed for composite particles?

I'm sure there is but I do not know how.

 

[CWatters]

As I understand it the Quantum Spin of a composite particle is the sum of the spins of it's components. So for a proton (three quarks) the overall spin Quantum spin is 1/2.

I'm no expert but I though particles had fixed quantum spin. As Wikipedia says..

http://en.wikipedia.org/wiki/Spin_(physics)#Spin_quantum_number

Selected quotes..

Those particles with half-integer spins, such as 1/2, 3/2, 5/2, are known as fermions, while those particles with integer spins, such as 0, 1, 2, are known as bosons.

Elementary fermions with other spins (3/2, 5/2 etc.) are not known to exist, as of 2013.

Elementary bosons with other spins (0, 2, 3 etc.) were not historically known to exist, although they have received considerable theoretical treatment and are well established within their respective mainstream theories. In particular theoreticians have proposed the graviton (predicted to exist by some quantum gravity theories) with spin 2, and the Higgs boson (explaining electroweak symmetry breaking) with spin 0.

In other words we haven't discovered particles with larger quantum spin than these values.

 

[emergentsystem]

First, I think it's important to understand that fundamental particles are considered to be point-like, meaning they have no size. As such, I'm not sure if the term "rotation" can be applied to them. (Perhaps their wavefunction can be rotated?) Composite particles and larger objects are limited by the strength of their bonds versus the centrifugal force of the rotation. And no object can be rotated so fast that any part of it meets or exceeds the speed of light.

I see. So everything except fundamental particles can be rotated fast enough to break apart? Are there any exceptions to this?

As I understand it the Quantum Spin of a composite particle is the sum of the spins of it's components.

I was actually more interested in maximum speed of physical rotation of particles, I should have been more clear. Thanks for your answer anyway.

 

[CWatters]

The man made record was broken in August this year...

http://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-23861397

University of St Andrews scientists create 'fastest man-made spinning object'

They were able to levitate and spin a microscopic sphere at speeds of up to 600 million revolutions per minute.

They saw it spin faster and faster until it reached 600 million rpm - and then it seemed to vanish!

The researchers don't know what happened to the sphere - but one possibility is that the object may have reached some theoretical speed limit - after which it changed in some way.

"The rotation rate is so fast that the angular acceleration at the sphere surface is one billion times that of gravity on the Earth surface. It's amazing that the centrifugal forces do not cause the sphere to disintegrate."

Perhaps they did.

 

[256bits]

Without moving in any direction, what is the maximum speed at which a particle can rotate? Does it depend on its mass or size?

Your question is a contradiction is it not, or rather the terms 'without moving in any direction' and 'particle' can be loosely defined.

If you are asking about anything other than fundamental particles such as protons, neutrons and electrons, which has already been explained, do not have a size but have an intrinsic angular momentum given the term spin, then that type of spin can be explained with an anology of a macroscopic object rotating about an axis but only so far. One can also include a composite particle such as the nucleus of an atom as having a spin.

A macroscopic object spinning about an axis has an angular momentum and that can be explained classically with equations. The equations will give the tangential velocity of a point as a function of the radius and also the radial acceleration that a point will experience as a function of the radius.

Are you asking about a particle of dust, a water mist particle, a marble, a top, or an object such as the earth? You might want to ponder the idea of when does a particle become an object.

If you consider the earth, it does as a whole rotate on its axis in addition to revolving around the sun. But are not the constituant parts of the Earth also revolving about an axis, with a velocity and change in direction. Would you consider yourself on the surface of the Earth to be spinning about an axis or rotating about an axis? So even if the Earth's rotation as a whole is described as 24 hours long, points on the Earth's surface or anywhere along its radius actually revolve about the axis.

The revolution about an axis is what gives rise to the centripetal force ( or centrifugal force if one wishes to look at it that way ) and the subsequent angular velocities and radial accelerations of points along a radius. The strength of cohesion of the object is what will determine whether an object ( of any size down to small particles ) will stay together as one or not during 'spinning'.

The reason I wrote this up as such is because I was thinking of Cern, Fermi Lab where elementary particles are following a curved path at near light speed, and if following the curve is a rotation or a revolution about an axis or a circulation gave me something to think about.

 

[CWatters]

Interesting. Let's do the numbers for the ring at Cern...

Circumference of 27km
Particles in it are going at the speed of light 3 * 10^8 m/s
Assume they rotate once per lap of the ring

That gives an answer of about 670,000 rpm.

I guess you would get a much higher figure if you looked at the tighter radius of a particle film track (eg in the experiment itself) but I couldn't easily google the radius of these tracks.

 

[emergentsystem]

Your question is a contradiction is it not, or rather the terms 'without moving in any direction' and 'particle' can be loosely defined.

Are you asking about a particle of dust, a water mist particle, a marble, a top, or an object such as the earth? You might want to ponder the idea of when does a particle become an object.

My thinking was that the object's location does not change, in that it's only movement is rotation. So it does not have any momentum other than angular momentum. Really I was interested in any sort of answer regardless of the size of the object, perhaps more can be said about rotation of larger objects.

The man made record was broken in August this year...

http://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-23861397

University of St Andrews scientists create 'fastest man-made spinning object'

This is very interesting. Is anything else known about strange properties that objects might obtain if they rotate fast enough?