Why do heavenly bodies spin?

[paigetheoracle]

Is there some connection between the reason balls spin and planets etc. in space? I ask this as a layman, who has noticed that balls travelling through the air rotate, whether thrown or kicked (Using a dog ball thrower this can be observed because when the ball hits the water, which acts as a brake, it is still turning; likewise a bouncing ball can be seen to spin).

Another observation that may be related to this is pushing a flat bottomed object over grass as opposed to ice. When travelling over the latter, the natural inclination is for it to spin,to maintain forward motion because of gravity causing friction, which is reduced when travelling over ice.

This ties in with my thread 'Why do UFO's spin?' in The Strange Claims forum as I'm speculating if there could be a connection between all these phenomena theoretically, even if Flying Saucers may not have been proved to be objectively real and not all incidents report this kind of movement either.

[modest]

The conservation of angular momentum says that when something very large rotates very slowly and shrinks to a smaller size - it will rotate faster. Think of an ice skater with their arms swinging out wide - they turn slow. When they bring their arms in close to their body they rotate faster. That's conservation of angular momentum.

Same thing happens when heavenly bodies form. A very large nebula of gas and dust may spin very, very slowly; but when it collapses it will conserve its angular momentum causing it to rotate much faster by the time it becomes a star. The process is similar for galaxy and planet formation.

There's no constant force making these things rotate. When you start something rotating in space it will continue rotating by Newton's first law. So, the rotation you see now is what's left from the original rotation when these things formed.

~modest

[CraigD]

Except for special cases involving objects that can stabilize themselves in some manner (eg: a paper airplane, or your example of something sliding across grass), nearly any collection of bodies held together by something (the gas of a star, the rocky material of a planet, held together by gravity, a football held together by leather and thread, etc.) are more likely to spin than not.

This is because there are many more possible initial conditions (eg: infalling gas and solids in a forming solar system) where the individual bodies making up a system have direction other than all toward the system’s center of mass. It is, in principle, possible to throw or kick a ball so that it doesn’t spin, but very difficult to do so. Likewise, a pre-stellar nebula could, in principle, collapse into a star with no rotation, but this would be an incredibly rare occurrence.

There are some astronomical objects that, on some scales, have little spin. Globular clusters are an example. The stars in them don’t orbit their center of gravity in fat ellipses, but in ones so thin they are nearly straight lines. The whole cluster sort of falls in on its own center, contracting into a dense ball, the then falls out again into a tenuous one.

You can run simulations to determine the probability of a particular gas/dust cloud forming a system with particular spin rates. The result (I assume – I’ve not personally done such a sim) shows that most systems behave something like our solar system, or the various other star systems we’ve observed.

[koji8123]

plus gravity?

[freeztar]

Originally Posted by koji8123

plus gravity?

Originally Posted by CraigD

Except for special cases involving objects that can stabilize themselves in some manner (eg: a paper airplane, or your example of something sliding across grass), nearly any collection of bodies held together by something (the gas of a star, the rocky material of a planet, held together by gravity, a football held together by leather and thread, etc.) are more likely to spin than not.

Yes.

[koji8123]

didn't see that, sorry

[Pluto]

G'day from the land of ozzzzzzzzz

The seed of a pepper corn tree is quite small and yet it is able to produce the same huge tree every time with a bit of variation that depends on the egology of the area.

Same with matter, subatomic particles have a spin and you would expect the seed to form matter that has a spin. Maybe this can be explained by the wave theory and the wave centres of every so called particle.

[Pluto]

G'day

Talking about spins

[0710.4073] Estimating the Spins of Stellar-Mass Black Holes by Fitting Their Continuum Spectra
Estimating the Spins of Stellar-Mass Black Holes by Fitting Their Continuum Spectra

Authors: Ramesh Narayan, Jeffrey E. McClintock, Rebecca Shafee
(Submitted on 22 Oct 2007)

Abstract: We have used the Novikov-Thorne thin disk model to fit the continuum X-ray spectra of three transient black hole X-ray binaries in the thermal state. From the fits we estimate the dimensionless spin parameters of the black holes to be: 4U 1543-47, a* = a/M = 0.7-0.85; GRO J1655-40, a* = 0.65-0.8; GRS 1915+105, a* = 0.98-1. We plan to expand the sample of spin estimates to about a dozen over the next several years. Some unresolved theoretical issues are briefly discussed.

[CraigD]

Originally Posted by Pluto

… subatomic particles have a spin and you would expect the seed to form matter that has a spin. Maybe this can be explained by the wave theory and the wave centres of every so called particle.

To the best of my knowledge, there’s no connection between spin in quantum mechanics and spin in classical mechanics (ie: angular momentum) we’ve been discussing in this thread. Note that, per the first linked article above:

the spin of quantum mechanical systems ("particle spin") possess several non-classical features and for such systems spin angular momentum cannot be associated with rotation but instead refers only to the presence of an 'angular momentum-like' property.

In short, the use of the word “spin” in quantum mechanics appear to be one of may cases where it’s connection to classical mechanics is only an analogy intended to help make the often counterintuitive formalism of QM more comprehensible. I’ve long wondered if this nomenclatural approach is effective – that is, if, when considering all potential students, it enhances or retards comprehension.

It’s pretty easy to show that particle spin and angular momentum are unrelated, via thought experiment such as the following:

• You have 2 solid spheres made of the same material (eg: iron cannon balls), one massing 1 kg, the other 100, floating in vacuum (eg: in outer space).
• By applying force to either sphere, you can give either one an arbitrarily great or small angular momentum. The small sphere can be made to spin fast, or the large one made to have no detectable spin.
• However, the total quantum spin of the particles in the spheres does not change. The 100 kg sphere has 100 times the total quantum spin of the 1 kg sphere.
• Therefore, there is no connection between the angular momentum of a macroscopic body and the quantum spin of its constituent particles.

[paigetheoracle]

Originally Posted by modest

The conservation of angular momentum says that when something very large rotates very slowly and shrinks to a smaller size - it will rotate faster. Think of an ice skater with their arms swinging out wide - they turn slow. When they bring their arms in close to their body they rotate faster. That's conservation of angular momentum.

Same thing happens when heavenly bodies form. A very large nebula of gas and dust may spin very, very slowly; but when it collapses it will conserve its angular momentum causing it to rotate much faster by the time it becomes a star. The process is similar for galaxy and planet formation.

There's no constant force making these things rotate. When you start something rotating in space it will continue rotating by Newton's first law. So, the rotation you see now is what's left from the original rotation when these things formed.

~modest

That's very interesting - so are you saying that as something shrinks, it spins faster? If so, would water going down the plug hole be an equal analogy because I've noticed it seems to spin faster at the end, when it gets to gurgling stage. Is there some connection then, between Quantam Mechanics ''spin' and larger bodies 'spin' - could this be it and is there something in here about black holes and star collapse, through the shrinking process? (Old, big and slow/ young, small and fast). Could this relate to all forms of reality and all forms of life? (Beaurocracy and anarchy) or am I jumping the gun with a theory of everything outlook? (Blasphemy! Heresy!...no, just wrong according to the evidence we have at present). Sorry if this seems a bit 'Strange Claims' area but I'm a layman trying to make sense of existence, not an astophysicist