Heres a little brain food, its a question that I think I know the answer to, but I want to see what you all think. If you take a three dimensional star and rotate it when will it become a perfect sphere? and by perfect i mean every single point (by the way, to creat the sphere the rotations of the points of the star form the surface of the sphere and you can rotate it in any direction)? :cool:

It wont. The only chance it has of becoming a sphere is if it does not rotate
Rotation will transform it into an oblate spheroid: how oblate will depend on the rate of rotation the mass and the density distribution

It wont. The only chance it has of becoming a sphere is if it does not rotate
Rotation will transform it into an oblate spheroid: how oblate will depend on the rate of rotation the mass and the density distribution
Sorry O,
The star matter was in an arbitrary shape ,"three dimensional" , and started spinning it would only take a spherical shape by a slight chance as the shape migrated to an oblate spheroid: This assume the rotation rate were within proper limits. Proper limits would be defines from the mechanical integrity of the star's 3 dimensional structure, which would certainly be temperature dependent, at least.
But consider this: if the mass was an oblate spheroid to begin with and the
if the rotation rate were suffciient large the mass will form as a circular disk directly. If the rotation rate were too slow the figure would end up in some oblate spheroidal. I can't see a shere beinmggenerated that was stable as a shere unless by chance it passed throuigh this phase while changing shape shape.

A star w/o rotation?. You are sugesting that gravity will equalize the internal structure to a sphere?

Maybe so, but mostly no, unless the elements of angular moment were to appear in the show.
Without no spin? well, there's always the winsom grin of Alice's cat. With no spin my dear that's where we'd be at.

Geistkiesel

Good. Unlike your origin of life post I can understand this one.Sorry O,
The star matter was in an arbitrary shape ,"three dimensional" ,

WT said nothing about an arbritary shape. He said nothing about star matter. He clearly stipulated a star. Not a proto-star, not a interstellar gas cloud, but a star.

......
and started spinning it would only take a spherical shape by a slight chance as the shape migrated to an oblate spheroid: This assume the rotation rate were within proper limits. Proper limits would be defines from the mechanical integrity of the star's 3 dimensional structure, which would certainly be temperature dependent, at least.This is gobbledegook. If you intend something here please be more precise. If, for sake of argument, the star is not spinning and is already an oblate spheroid (though I cannot imagine what set of circumstances would permit an oblate spheroid to persist in a gaseous body), then begins to spin, there are no circumstances it which it could by a slight chance become spherical. Its oblateness would simply increase. Agreed?
In short, and to repeat my original statement, only a non-spinning star can adopt the form of a perfect sphere. What do you find difficult to understand in this?
if the mass was an oblate spheroid to begin with and the
if the rotation rate were suffciient large the mass will form as a circular disk directly. If the rotation rate were too slow the figure would end up in some oblate spheroidal.

Exactly why I have rejected any spinning star as being capable of forming a perfect sphere.

A star w/o rotation?. You are sugesting that gravity will equalize the internal structure to a sphere?
Yes. Precisely. What was so difficult about that?

Maybe so, but mostly no, unless the elements of angular moment were to appear in the show.
Without no spin? well, there's always the winsom grin of Alice's cat. With no spin my dear that's where we'd be at.

G, if it's not spinning there is no angular momentum to consider. Unlikely? I would have thought impossible, or nearly so. But WT asked how could a star become a perfect sphere. The practical answer is "it cannot", the theoretical answer is the one I gave "by not spinning".

Good. Unlike your origin of life post I can understand this one.

WT said nothing about an arbritary shape. He said nothing about star matter. He clearly stipulated a star. Not a proto-star, not a interstellar gas cloud, but a star.
No, he said the star was 3 dimensional, meaning a general shape.

This is gobbledegook. If you intend something here please be more precise. If, for sake of argument, the star is not spinning and is already an oblate spheroid (though I cannot imagine what set of circumstances would permit an oblate spheroid to persist in a gaseous body), then begins to spin, there are no circumstances it which it could by a slight chance become spherical.If the stuff was in some arbitrary 3 dimensional configuration and started spinning from the force applied by a passing stellar object, then as the shape started to alter and beging to form in a general round 3 dimensional shape, then under conditions of proper rotation rate, temperature, skewed forces, unablanced forces due to shape change occurred, the migrating shape (shape 1 -> shape2 -> . . .->shapen) could fall through a spherical shape for an instant just by sheer randomness. I am no saying it is guaranteed to do so, only that it could by chance.
Your "gobbledegook" charge regarding a 'precious' of mine needs editing. You troubled my feelings with that.


Its oblateness would simply increase. Agreed?

Under my conditions stated above , agreed.

In short, and to repeat my original statement, only a non-spinning star can adopt the form of a perfect sphere. What do you find difficult to understand in this?


Exactly why I have rejected any spinning star as being capable of forming a perfect sphere.

Yes. Precisely. What was so difficult about that?


G, if it's not spinning there is no angular momentum to consider. Unlikely? I would have thought impossible, or nearly so. But WT asked how could a star become a perfect sphere. The practical answer is "it cannot", the theoretical answer is the one I gave "by not spinning".
O, look at what WT said:
"If you take a three dimensional star and rotate [emphasis added, G] it when will it become a perfect sphere? and by perfect i mean every single point (by the way, to creat the sphere the rotations of the points of the star form the surface of the sphere and you can rotate it in any direction)?

The difficulty is :
I read 3 dimensional star to mean any arbitrary shape.
I read that one of the problem parameters was a rotating mass. Not once did WT mention spinning, but thrice!
I interpreted the problem from the perspective the parametrs mentioned and depending on the
original shape, temperature, density, chemical/nuclear activity, spatial imbalances in mass, other when discovered

You didn't read the problem and mentally skip those parts that you couldn't handle and then relaxed in to your "it ain't spinning" dialogue did you" Just asking, chill O.
Geistkiesel

I don't think it logical to think of a star as a random 3D shape. If WT meant that he was imprecise. If you took this interpretation you were illogical. All stars, as far as we know, are oblate spheroids.
Once you had taken this step, which I think erroneous, your conclusions appear valid, in that restricted context.
It is specious of you to introduce temperature, density, chemical/nuclear activity, spatial imbalances in mass,and then not use them in anyway. I could just as readily introduce these equations:

dP/dr = -GM(r)rho(r)/r^2 hydrostatic equilibrium

dM/dr = 4*pi r^2 rho(r) the mass equation

dT/dr = [-3K(r)rho(r)/(64*pi sigma r^2 T^3(r)]L(r)
Energy Transport

dL/dr = 4*pi r^2 rho(r) epsilon(r)
Energy Generation

Which will indeed determine the stellar structure, and look very impressive.

They remain, however, wholly incidental to the fact that a bona fide star cannot be a true sphere, because it is rotating.

I now wait in eager anticipation for WT to return and prove me wrong thus:

Neutron stars are very dense. They also slow down with time. Given enough time they will stop spinning completely. A non-spinning neutron star, under the influence of its concentrated gravity field will be a perfect sphere.

I don't think it logical to think of a star as a random 3D shape. If WT meant that he was imprecise. If you took this interpretation you were illogical. All stars, as far as we know, are oblate spheroids.
Once you had taken this step, which I think erroneous, your conclusions appear valid, in that restricted context.
It is specious of you to introduce temperature, density, chemical/nuclear activity, spatial imbalances in mass,and then not use them in anyway. I could just as readily introduce these equations:

dP/dr = -GM(r)rho(r)/r^2 hydrostatic equilibrium

dM/dr = 4*pi r^2 rho(r) the mass equation

dT/dr = [-3K(r)rho(r)/(64*pi sigma r^2 T^3(r)]L(r)
Energy Transport

dL/dr = 4*pi r^2 rho(r) epsilon(r)
Energy Generation

Which will indeed determine the stellar structure, and look very impressive.

They remain, however, wholly incidental to the fact that a bona fide star cannot be a true sphere, because it is rotating.

I now wait in eager anticipation for WT to return and prove me wrong thus:

Neutron stars are very dense. They also slow down with time. Given enough time they will stop spinning completely. A non-spinning neutron star, under the influence of its concentrated gravity field will be a perfect sphere.
I can see that you aren't budging. I had that little list of parameters to indicate some considerations of the star attributes that is in the process of start-up of the mass' initial spinning. :cool:

Now from the vehemence of your reply I presume that your consideration of just exactly what is a star might be different than mine when considering "when" is a star. Is the mass assembled that will ultimately come toghether as the final product a star, or is the mass a star when all the final mass is identified, perhaps still in the "gaseous" phase?

I am not teasing you nor sticking you with esoteric nonsense barbs for the purpose of you jumping in my face. I suspect that WT had neither of our models in mind. But, can you see my approach? there is a gaseous mass that is supposed to gell, solidify through the actions of particle-particle gravity. Does it seem unreasonable to take the question to some logical beginning and start the analysis there? If you want to start from your point of view go tight ahead but to discount my POV because it desn't fit within your definitional limits seems unfair, to yourself I mean.

I can continue in my reasoning processes until the gas phaise of the "star" evolves to something recognizable as within you definitional limits. You miss the exercise by virtue of an axiomatic barrier that diverts your thinking from 1st principals and forces the reasoning protocol to soemthing familiar such as "formulae by the book". Yournumbers are impressive but , unfortunately only approximations that contain no useful physical information that aid us in arriving at a solution. The equations you brought out were not intended as tools useful in the solution of the problem, rather the tools are offered as scorn and sarcasm as if useful for some purpose here.
I don't mind a bit if you get the right answer and I get the wrong answer, this is just us not my concern.

Geistkiesel

Geistkiesel
your opening post said, in essence "Ophi, you are wrong."
My subsequent posts have done three things:
1. Demonstrated that I am not.
2. Conceded that if you take an unconventional (and in my view technically very wrong) definition of a star, then you are also correct. [But really, go check your basic astronomy texts for a definition that comes close to yours, and doesn't have proto in front of it.]
3. I challenged your pointless inclusion of pseudo technical terms by posting some of my own. Sorry if being caught out in another debating trick spoiled your day.

So, to more interesting matters: how long would it take for a neutron star to slow to a stop, do you suppose?

Well, my original idea conforms to O's idea but for a different reason. I admit when i said star i should have stated a three dimensional version of a two dimensional star rather than the sun or anything else like a red giant etc. The reason had come up with was that even at a high speed and consistent rotation (even if it left matter behind where it had spun) it cant become a sphere because a perfect sphere has an infinite number of points on the surface and inside it so unless you take the star and reform it, it wont work, i think that might be flawed logic, but thats what i thought

Onto the neutron star, the star would stop rotating under a specific set of circumstances such as: The star running out of fuel and then running out energy. Another possibility is that it would never stop rotating but other things would have to interfere with it to make it happen, like asteroids and being fueled by a nearby star... sorry if you were looking for a mathematical explaination, that i dont know

Well, my original idea conforms to O's idea but for a different reason. I admit when i said star i should have stated a three dimensional version of a two dimensional star rather than the sun or anything else like a red giant etc. The reason had come up with was that even at a high speed and consistent rotation (even if it left matter behind where it had spun) it cant become a sphere because a perfect sphere has an infinite number of points on the surface and inside it so unless you take the star and reform it, it wont work, i think that might be flawed logic, but thats what i thought
From that perspective nothing is a perfect sphere, since it must be made of atoms, which have spaces within and between. An atom is a good analogy, because it rotates so quickly that it might as well be a sphere.

Geistkiesel
your opening post said, in essence "Ophi, you are wrong."
My subsequent posts have done three things:
1. Demonstrated that I am not.
2. Conceded that if you take an unconventional (and in my view technically very wrong) definition of a star, then you are also correct. [But really, go check your basic astronomy texts for a definition that comes close to yours, and doesn't have proto in front of it.]
3. I challenged your pointless inclusion of pseudo technical terms by posting some of my own. Sorry if being caught out in another debating trick spoiled your day.

So, to more interesting matters: how long would it take for a neutron star to slow to a stop, do you suppose?
Your disclaimer in 3. is not necessary. Besides remember the words of our country's greaest dramatic persona, John Wayne, who artfully recognized the value to, "Don't apologize, it's sign of weakness".

You called my use of "pseudo technical terms" when I inimated that for the mass of a forming star still in a gaseous state that the paramters listed temperature, etc would all be significant in the 3 dimensional formation of the star;assuming some angular velocity component imposed by a passing stellar mass then as the gas volume diminshed and as the volume progressed to the inevitable oblate spheroidal shape there would be a possibility, as slight as it may be that that the 3D form would take in the O Model below. If you read the graph from back-red to black-sphere to front-white you will be able to follow the path of formation - to equilibrium - in the inevitable white centered oblate sphereoid. . . .if only for an instant, for a just short spec in time that the star be perfectly spherical . . .. And who would deny this poor man that which takes from the path but a bit of the lonliness? (http://www.sciforums.com/attachment.php?attachmentid=3864&stc=1)

The armament you showed with your 'exposure of my trick' was a valid and expected response in a scientific discussion on levels that we are engaging ourselves. There be no sense in characterizing your armament as mere rhetorical propaganda tools.
Geistkiesel