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]

plus gravity?

 

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]

… 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]

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:naughty::doh::naughty:

[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.

 

Yes. A water particle or anything else moving with a whirlpool (free vortex) does conserve its angular momentum.

 

Angular momentum is here tangential velocity times radius from center of rotation:

 

L(angular momentum) = V(velocity) X R(radius from center)

 

Since angular momentum stays constant V and R are inversely proportional. As V gets bigger, R must get smaller and vice versa. This means water further from the hole is expected to have less velocity than closer water. This is consistent with water forming a whirlpool and the link above does a bit to explain that.

 

Is there some connection then, between Quantam Mechanics ''spin' and larger bodies 'spin'

 

CraigD addressed this in the post preceding yours.

 

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:naughty::doh::naughty:

 

I'm not sure where you're coming from here. Perhaps a thread in strange claims would be a better place to discuss such a proposition.

 

~modest

[Pluto]

G'day CraigD

 

 

I agree with what you say. You expalin it to the T.

 

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.

 

I was thinking along the lines of wave centres. Each part adds to the same direction spin.

[paigetheoracle]

Could the fact that heavenly bodies spin, be proof of the big bang? (Considering my observations and questions on this subject or has this already been thought of?).

[paigetheoracle]

Parkes radio telescope in Australia has discovered a pulsar wobbling on its axis, helping confirm Einsteins theory of gravity. Is it known what happens to a body in precession, in space? Does it react differently to a spinning top on Earth, which careers all over the place when spin is lost and if so why?

__________________

[CraigD]

Could the fact that heavenly bodies spin, be proof of the big bang?

I don't think so.

 

Astronomical bodies and systems of bodies - planets, stars, stellar systems, galaxies, etc. - are predicted to spin by any theory that assumes classical and/or relativistic mechanics to be at least roughly accurate on astronomical scales. Every cosmological theory I've ever heard of - Big Bang theories, with and without inflation, steady state theories, etc. - assume this, so all predict that the universe should be moving about like it's observed to.

 

There are some subtle differences between different theories of mechanics precise predictions of various motions - for example, between a purely Newtonian and General Relativities predictions of the precession of the orbit of Mercury - but nothing as dramatic as a prediction that rotation and revolution, or their absence, should be much more or less common than observed.

 

One occasionally hears or reads very vague, speculative ideas along the lines of Mach's principle (which isn't really a scientific principle, but more of a philosophical guideline for speculation) in which the absence of large-scale spinning might have profound consequences - for example, the idea that if systems were not rotating relative to the universe as a whole, they'd not have their usual momentums - but to the best of my knowledge, no well developed theory makes such predictions, and as there's no practical way to experimentally test such predictions (how can you make the whole universe stop moving?), so the subject is mostly one of philosophical recreation, not rigorous science.

 

Parkes radio telescope in Australia has discovered a pulsar wobbling on its axis, helping confirm Einsteins theory of gravity.

I think Paige is referring to the recently published study of the double pulsar PSR J0737-3039A/B (see 35540).

Is it known what happens to a body in precession, in space?

Though the detailed calculations are way above my head, yes, I believe this is pretty well-known and explained stuff.

 

Though we know that at some point, General Relativity will need to be radically revamped, because it doesn't include important known phenomena on very small scales, observations like these recent ones show that it continues to do very well on astronomical scales.

Does it react differently to a spinning top on Earth, which careers all over the place when spin is lost and if so why?

Rotating pulsars behave differently than spinning toy tops, because they are subject to very different collections of forces. A pulsar has a very large mass and angular momentum relative to friction and external forces (such as the gravitation attraction of a nearby companion body), while a toy top has a small mass and angular momentum, is subject to the constant large forces of gravity, a tabletop or whatever is opposing gravity, and air and mechanical friction.

 

The “careening all over the place” Paige describes is, I think, less a description of a mechanical prediction, than of what's commonly called chaos. Very small differences in initial conditions - ie: the position and speed of the top when it's launched - result in large discrepencies in in its predicted behavior later on. Therefore, no matter how precisely we measure a toy top's initial state, it's practically impossible to predict its precise position and velocity later on. Many systems, not just rotating ones, exhibit chaotic behavior.

 

 

I’ve noticed a tendency for people to regard the spinning of heavenly bodies as unexpected and significant, rather than overwhelmingly likely and signifying only that likely outcomes are observed more often than unlikely ones. I think this is because, as with many physical phenomena, our intuitions are tuned to everyday phenomena on the surface of Earth. In our everyday experience, things set to spinning – a wheel on an axle, a stone on a patch of ice, etc. – quickly stop due to friction. In the high momentum, low friction domain of outer space, however, this intuition serves us false. Although there are many examples of actual friction and friction-like phenomena in space (such as the tidal locking of the Moon to always point the same hemisphere at Earth), the norm, in space, is for objects set to spinning to continue spinning for a long time.

[paigetheoracle]

I don't think so.

 

Astronomical bodies and systems of bodies - planets, stars, stellar systems, galaxies, etc. - are predicted to spin by any theory that assumes classical and/or relativistic mechanics to be at least roughly accurate on astronomical scales. Every cosmological theory I've ever heard of - Big Bang theories, with and without inflation, steady state theories, etc. - assume this, so all predict that the universe should be moving about like it's observed to.

 

There are some subtle differences between different theories of mechanics precise predictions of various motions - for example, between a purely Newtonian and General Relativities predictions of the precession of the orbit of Mercury - but nothing as dramatic as a prediction that rotation and revolution, or their absence, should be much more or less common than observed.

 

One occasionally hears or reads very vague, speculative ideas along the lines of Mach's principle (which isn't really a scientific principle, but more of a philosophical guideline for speculation) in which the absence of large-scale spinning might have profound consequences - for example, the idea that if systems were not rotating relative to the universe as a whole, they'd not have their usual momentums - but to the best of my knowledge, no well developed theory makes such predictions, and as there's no practical way to experimentally test such predictions (how can you make the whole universe stop moving?), so the subject is mostly one of philosophical recreation, not rigorous science.

 

I think Paige is referring to the recently published study of the double pulsar PSR J0737-3039A/B (see 35540). Though the detailed calculations are way above my head, yes, I believe this is pretty well-known and explained stuff.

 

Though we know that at some point, General Relativity will need to be radically revamped, because it doesn't include important known phenomena on very small scales, observations like these recent ones show that it continues to do very well on astronomical scales.Rotating pulsars behave differently than spinning toy tops, because they are subject to very different collections of forces. A pulsar has a very large mass and angular momentum relative to friction and external forces (such as the gravitation attraction of a nearby companion body), while a toy top has a small mass and angular momentum, is subject to the constant large forces of gravity, a tabletop or whatever is opposing gravity, and air and mechanical friction.

 

The “careening all over the place” Paige describes is, I think, less a description of a mechanical prediction, than of what's commonly called chaos. Very small differences in initial conditions - ie: the position and speed of the top when it's launched - result in large discrepencies in in its predicted behavior later on. Therefore, no matter how precisely we measure a toy top's initial state, it's practically impossible to predict its precise position and velocity later on. Many systems, not just rotating ones, exhibit chaotic behavior.

 

 

I’ve noticed a tendency for people to regard the spinning of heavenly bodies as unexpected and significant, rather than overwhelmingly likely and signifying only that likely outcomes are observed more often than unlikely ones. I think this is because, as with many physical phenomena, our intuitions are tuned to everyday phenomena on the surface of Earth. In our everyday experience, things set to spinning – a wheel on an axle, a stone on a patch of ice, etc. – quickly stop due to friction. In the high momentum, low friction domain of outer space, however, this intuition serves us false. Although there are many examples of actual friction and friction-like phenomena in space (such as the tidal locking of the Moon to always point the same hemisphere at Earth), the norm, in space, is for objects set to spinning to continue spinning for a long time.

 

Excellent reply! Usually CraigD leaves himself open to attack by people like me (Well me in particular) but I believe this covers everything very well. I personally wouldn't expect things in space to behave like they do in space - hence the question. You mention chaos as the likely outcome of loss, of momentum and spin: It's a bit like saying that life without motion leads to and is death (chaos) as well, meaning to me at least that both systems couldn't exist without some kind of movement (hold their form). Does this tie in with Quantam Mechanics and the atom, even though the laws governing this level of reality is so different or should I be asking this in the physics forum?