Why is everthing spinning ?

[impactcrater]

I am puzzled why everything in the Universe is spinning.....many objects from the smallest to the largest are spinning about an axis...Where did all this angular momentum come from?

[Charic]

Where did it come from?......Interstellar gases and dust has motion/movement and who/how its stirred, I've no idea, that's another question?

This movement or rotation is known or described as 'Angular Momentum' so  When the Planets and Stars form from the collapse of  the interstellar clouds, the Stars and Planets that form inherit/maintain this angular motion, and continue to rotate about their axis.

So the experts say 

Edited January 31, 2016 by Charic

[andrew s]

Getting rid of angular momentum (spin) is the big issue in astrophysics not where it came from. Any two objects moving relative to each other unless perfectly aimed at each others center of mass have rotation (angular momentum) relative to each other. All you need to set this going is some small fluctuations at the start of the universe to break the perfect symmetry.

The spin of fundamental particles is not the same although spinning tops etc are often used as an analogy. In fact it has no classical counterpart.

Regards Andrew

Edited January 31, 2016 by andrew s

[Stu]

My understanding is that as the gas and dust clouds collapse, there are always imbalances as the cloud is never a perfect sphere. These imbalances result in a slight spin starting as the cloud collapses, which gets faster as the cloud gets smaller and more dense. I guess this is akin to the example of a skater spinning faster as they pull their arms in and put them above their heads. Finally the cloud gets enough spin to flatten out into a disc from which the solar system forms. Similarly with planets, they will inherit the spin from the proto-planetary disc which is maintained and increased as the planet coalesces.

[xtreemchaos]

heres a stab in the dark, blackholes,  movement or rotation  spread out through universe with graverty like eddys in water. told ya it was a stab in the dark.charl.

[Mr Spock]

Within the quantum world 'spin' is an entirely different concept. It would take a dozen pages and a larger brain than mine to explain it!

[vlaiv]

Rotational motion (spinning) scares me a bit, I must say.

For one, it is accelerated motion without usage of energy. Take for instance Einstein's elevator thought experiment. If you are in elevator (closed box with no windows) and either suspended in gravity field, or uniformly accelerating in strait direction - you would not know the difference. Same being if elevator is aboard a space station that is rotating about it's axes. Once space station is spun around it's axes you do not need additional energy to keep it spinning. But effects of it would be indistinguishable to the observer in elevator from gravity or uniformly accelerating in forward direction. Well I think this is not exactly true, at least for uniformly accelerated motion not being distinguishable. For both spinning and gravity one could in theory detect force gradient, but not for uniformly accelerated motion.

Take another example of it's strangeness. Let's imagine two spaceships, floating with uniform velocity related to each other. Which one is moving and which one is standing still? Of course relativity gives answer - depends on your reference frame (no single correct answer). Certainly no way for observer on any of them to tell. But let's suppose following: two circular (shape of wheel) spaceships (like one in Space Odyssey) are aligned on their axes (like for example front wheels of the car relative to each other). If one of them is spinning around that axes, for observers in space stations / ships it would appear as the other one is spinning in opposite direction (both would see other ship spin, similarly as in first case where each see other ship moving relative to him/her). But which is spinning? Here we have really simple way of telling - one that can detect centrifugal force being exerted on objects.

This one really twists my brain: let's say I move 1 meter in some direction. In effect, I moved whole universe 1m in opposite direction. But if I spin for half of a circle around my axis, I've "moved" some things in universe much larger distance than others. I moved some particular galaxy very far away, billions and billions of light years from its original position . Point being here that coordinate transformations and distances to original positions are quite different for translation and rotation - I certainly don't move whole universe .

And of course there is gyroscopic effect. That thing just bleeds my brain dry when thinking about it.

So I guess that answer to question why is everything spinning, has something to do with this scary strangeness of spinning itself.

[Stu]

Coming back to the original point, doesn't the energy for the spin come from the gravitational potential energy the gas/dust cloud has before it collapses? As it collapses this potential energy is converted into angular momentum????

[vlaiv]

12 minutes ago, Stu said:

Coming back to the original point, doesn't the energy for the spin come from the gravitational potential energy the gas/dust cloud has before it collapses? As it collapses this potential energy is converted into angular momentum????

It certainly does. From gravity and asymmetry of matter distribution or something like that. Take the following: 2 perfect balls and gravity and nothing else. No initial velocities. You will not get rotational motion, balls will just oscillate - fall towards each other, bounce off and return to original positions. For 3 balls you can only have this if they are placed at vertices of equilateral triangle and so on ... You have to have perfect symmetry for oscillatory motion, otherwise it turns into rotational. One can speculate that rotation of things in universe is consequence of gravity and perhaps uncertainty principle (big bang was not perfectly symmetrical or something).

[michaelmorris]

My guess is that on a large scale is that spin occurs due to gravity.  Gravity bends space/time, therefore making the path photons and matter take to be curved.  Anything following a path that is not directly towards the centre of mass of the object generating gravity will cause the photon/mass to follow the curved space caused by the gravity.

[andrew s]

36 minutes ago, michaelmorris said:

My guess is that on a large scale is that spin occurs due to gravity.  Gravity bends space/time, therefore making the path photons and matter take to be curved.  Anything following a path that is not directly towards the centre of mass of the object generating gravity will cause the photon/mass to follow the curved space caused by the gravity.

Indeed on a large astronomical scales it is due to the energy released during gravitational collapse. As mentioned above you need a degree of asymmetry which can come about in many ways, two examples being, an initial non-uniform mass distribution and friction induced turbulence.  You don't need strong gravitational fields curving space time. Even in star formation good old Newtonian gravity is sufficiently accurate.

Classical dynamics has been able to explain the spin of classical objects (i.e. non quantum spin) for 100's of years it is not at all a mystery. However, the effects of the conservation of angular momentum can be counter intuitive. Also one needs to make a distinction between what are known as pseudo-force which can't be measured using an accelerometer and real forces which can. 

Regards Andrew

Edited February 1, 2016 by andrew s