Re: [Vo]:Black Holes from Newtonian Gravity? - discs.gif

[Michel Jullian]

I agree on all points except your coincidental remark that "We are in
a galaxy colliding with the Milky Way",  isn't the Milky Way our
galaxy (as etymology indicates) any more?

Michel

2008/10/14 Horace Heffner <[EMAIL PROTECTED]>:
>
> On Oct 13, 2008, at 3:59 AM, Michel Jullian wrote:
>
>> Agreed. I think the misunderstanding arises from Robin talking about
>> the field _inside_ the disk, and the two of us talking about the field
>> _near_ the disk, i.e. that felt by matter ejected out of the disk
>> thickness.
>>
>> Michel
>
>
> This is true.  I am talking about an idealized situation, a planar charge
> (mass) of uniform density rho, and the field immediately surrounding it and
> generated by it.  However, a thin disk of approximately uniform density
> approximates this.  Matter passing through the z axis of an x-y plane disc
> of finite thickness will see a reducing z axis field which reaches a minimum
> of zero at z=0.  Matter that remains close to a thin disk, except when
> passing through the disc, will see an approximately uniform z axis field
> that produces periodic motion about the plane of the disk. In the case of a
> thin but finitely thick disc of uniform density the local fields near the
> disk overwhelm the more remotely generated fields, even out a radial
> distance that is a fairly good percentage of the disc diameter away from the
> center of the disc.  Such a disc then approximates an infinite plane. The
> closer you are to the center of a plane segment without being within the
> plane the closer it approximates an infinite plane.   Except at the
> periphery, the boundary, the closer you are to a thin disk without being
> within the disk the closer it approximates an infinite plane.  The radial
> field of a thin uniform disc, just outside the disk, but not out near the
> radial periphery of the disk, is small in comparison to the z axis field.
>  It is the material that moves in the z axis with respect to the disk that
> would end up in a polar jet by a slingshot scenario, and which would
> approach a central black hole from a polar direction.  Material approaching
> a black hole in the plane of its spin would not end up in a jet via a
> sligshot mechanism, unless perturbed by material having a z axis component,
> but maybe could by a compression scenario.
>
> That's my impression anyway.
>
> It is coincidental perhaps the solar system is currently passing through the
> plane of the Milky Way, though the Milky way has an arm structure and is
> thus not a planar disk.  We are in a galaxy colliding with the Milky Way, so
> the mechanics of our future motion is complex and possibly chaotic.  A near
> pass with another star or stars could send us in most any direction.  This
> is not a comforting thought.
>
> Best regards,
>
> Horace Heffner
> http://www.mtaonline.net/~hheffner/
>
>
>
>
>