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Re: Physicists Howl at Dark Matter

Subject: Re: Physicists Howl at Dark Matter
From: Lester Zick
Date: Thu, 21 Sep 2006 10:53:45 -0700
Newsgroups: sci.astro, sci.math, sci.physics, sci.skeptic
On Wed, 20 Sep 2006 17:00:00 -0600, Virgil <virgil@xxxxxxxxxxx> wrote:

>In article <fpg3h29d58mifqlcfiet1lr5653a0ds0g8@xxxxxxx>,
> Lester Zick <dontbother@xxxxxxxxxxx> wrote:
>
>> On Wed, 20 Sep 2006 14:18:31 -0600, Virgil <virgil@xxxxxxxxxxx> wrote:
>> 
>> >In article <5eu2h2t6rol73qhkd8q89cod54f2s45ggk@xxxxxxx>,
>> > Lester Zick <dontbother@xxxxxxxxxxx> wrote:
>> >
>> >> On 14 Sep 2006 18:47:35 -0700, QncyMI@xxxxxxxxxxxx wrote:
>> >> 
>> >> >yeah, prove that geometrically using calculus or
>> >> >just algebra . . .
>> >> 
>> >> Where m1 is aggregate gravitationally attractive mass
>> >> in a disk of uniform thickness and density in which the
>> >> amount of gravitationally attractive matter ~ area=rrpi
>> >> times unform thickness d:
>> >> 
>> >> As a function of radius r the aggregate force of gravitational
>> >> attraction will be:
>> >> 
>> >> F=Gm1m2/rr=Gm1(rrpi)m2/rr=Gm1(pi)m2 and
>> >> 
>> >> dF/dr=0 and gravitationally attractive force is constant as a function
>> >> of radius r: hence tangential velocity of all m2's will remain
>> >> constant as a function of radius r.
>> >> 
>> >> QED.
>> >> 
>> >> ~v~~
>> >
>> >Zick's derivation above presumes the the gravitational attraction  on a 
>> >unit mass due to a uniform thin ring of mass at a point in the plane of 
>> >that ring and inside the ring is zero. 
>> >
>> >And it presumes that at a point in the plane of the ring but outside the 
>> >ring the force is equal to that exerted by an  an equal mass 
>> >concentrated at the center of the ring.
>> >
>> >Both these assumptions are false.
>> >
>> >Perhaps Zick is being mislead by Newton's result for a thin spherical 
>> >bubble of mass, for which similar arguments are true.
>> 
>> I think it more likely that Zick is being mislead by charasteristics
>> of inverse square gravitation.
>
>Then Zick should note that the gravitational attraction at a point on 
>its circumference due to a mass evenly spread over a circular disc is 
>not equal to that of the same mass concentrated at the center of the 
>disc.

Remarkable, professor. I reach my conclusion that gravitationally
attractive force over a circular disk of uniform density is not a
function of radius through tedious calculation and you reach your
miscellaneous conclusion apropos of nothing in particular through what
exactly, the trivium of truth and tedium of divine inspiration?

>So that Zick's analysis is faulty.

And which of my equations is faulty pray tell?

~v~~

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