(TFT) hollow Cidri

["David Michael Grouchy II" <david_michael_grouchy_ii@hotmail.com>]

> From: Joe Hartley <jh@brainiac.com>
>
> . . .  I think that the assumption of an equal mass is incorrect, and that 
> you could use a value for mass easily
> enough to make Cidri's gravity similar to Earth's without it
> being unrealistic.
>
>     This may or may not require hollowness in the center
> of the planet, though I tend to think it does.

   Yes I can do this.  I can find a way to make it work.  And specifically 
with an anti-grav object in the middle as was originally suggested.  The 
total mass will be substantially greater, but the way it behaves is 
different.

    The program I'm tinkering with now uses gravity to run a stable solar 
system.  In the process I have learned quite a bit about the nature and math 
of Newtonian physics.  First off I have solved the "two body" problem so I 
can run the 88 largest bodies simultaneously.  Secondly as Newton invented 
Calculus to prove, no matter the shape of the body gravity may be assumed to 
originate from the center of mass.

    Without going into it, and just leaping to terminology I'm currently 
steeped in, the proposal would change the planet from having a "center of 
mass" to having a "gravity corona."  And then, yes, it becomes entirely 
possible.  But to illustrate the elegance that I saw in Scot's suggestion I 
wanted to first summon the problems that it eventually solves.

doubling the radius = 1/40 grav      if you are still using center of mass.  
(already posted)

the second post I had written....

> But if we make all life 1/40th the size of earth normal....
>
> we would have 160 x the surface area of earth
>
> and...
>
> everyone could walk on water.
>
> David Michael Grouchy II

    To show that certain key behaviors of physics would give away any 
changes in scale.

    And the planed third post would introduce the concept of a "gravity 
corona" with appropriated descriptions and supporting arguments.  Instead I 
just submit the pure math here in the form of an algorithm.  In my gravity 
lab program the following works.  And elegantly at that.

d := DistanceSqr(p1,p2);
d := d - (p2.corona_radius * p2.corona_radius);
d := 1/d;
d := d * p2.mass * GRAVITY_CONSTANT;

    Then just normalize and apply to the vector.  Of course one could also 
just subtract the corona from the distance before taking the square.  
Instead of subtracting the square of the corona.  Either way.  All physics 
would behave properly.  From the moon staying in it proper orbit to apples 
hitting the ground at the right speed.  That and the surface tension of 
water will be what we are used to.
    The neatest by product of this is that objects near the center are 
drawn outward.  Just as suggested people will be able to walk along the 
inside of the hollow earth.  What a coincidence it is that I happen to be 
working in the area planet creation and stable solar systems.  At this point 
I can make no informed comment on tides though.

David Michael Grouchy II
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