reply to post by Sinter Klaas
I believe Mnemeth is convinced there is another cause. Something electric.
Oh, am very aware of what Mnemeth believes. The is no credible researcher or theorist or scientist anywhere that follows that 'electric theory',
though. It is simply wrong for a simple reason: Electricity won't conduct unless there's something for it to travel through. Vacuum is the
(The following is my -- clumsy -- and purely unscientific understanding of gravity, locally):
Moving on --- the actions and calculations of gravity, on a planetary scale, are fairly prosaic, anyway. The larger questions are a comological and
universal concept, that are still being refined.
But, locally, for one planet at a time, it is highly, highly implausible for the "hollow" theory to be an explanation, let alone a theory.
First, there is simply no natural mechanism to explain such a formation. Second, back to the local effects of gravity -- they are undeniable, and
relentless. They WILL compact every last bit as tightly as possible, depending on the overall mass of the constituent material. Otherwise, smaller
bodies --- asteroids, comets, etc would not form.
But, that is all moot, when we examine the Earth, and compare its mass. It CAN be calculated, the total mass, and confirmed from celestial
Here, this describes calculating the mass:
Calculation: Mass of earth
We calculate Earth’s mass as follows:
Everything pulls on everything else in a simple way that involves only mass and distance. Newton said every body attracts every other body with a
force that, for any two bodies, is directly proportional to the product of the masses of the bodies and inversely proportional to the square of the
distance separating them.
The equation, expressing Newton’s statement, is
(1) F = G (m1) (m2) / d²
where G is the gravitational constant.
Newton also said that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net
force, and is inversely proportional to the mass of the object.
The equation, expressing this statement, is
(2) a = F / m.
We substitute Earth’s mass (me) and Earth’s radius (r) in Equation (1) to get the force that Earth attracts a body of mass (m) on the surface of
(3) F = G (me)(m) / r²
We substitute the acceleration (g) due to gravity in Equation (2) to get the force that the object of mass (m) resists the acceleration due to
(4) F = mg
To calculate Earth’s mass, we equate the forces given by Equations (3) and (4) and solve for (me). We get
(5) me = g r² / G
where the constants are given by G = 6.67300 x 10-11m³/(kg s²),
g = 9.8 m/s²
Because we evolved here, and this is "home base", and the planet we are most familiar with, we have assigned the average effect of the Earth's
mass the value "One G", 'G' for 'gravity'. That is our standard, thanks to work by Galileo and Newton. Using that as the unit, ALL other
calculations fit, mathwise. This is irrefutable, as well, as proven by the many successful space missions to other planets, and the Moon.
Again, with the mass of the Earth a defined value, we compare to the SIZE, which we also know with a great deal of accuracy. Knowing the diameter
gives us the volume; the total volume encompassed by the sphere. ("Flattened" sphere, but that's not important, not to any significant digit in
So, knowing the volume, and mass, the average density is easy to determine.
In order for thre to be an enormous "hollow void" internally, the rest
of the structure of the Earth, the so-called "shell", would
have to be made of material far, far more dense than mere rock. I don't have the skills to do the math --- possibly even solid lead wouldn't be
sufficient. Or, even the heaviest element on the Periodic Table!! (AND, we also know for certain that such elements don't exist in the required
quantity, anyway...not enough to form an entire planet, even "IF" 'hollow').
In fact, in order for the mass of the planet, "IF" 'hollow', to match its size, some exotic other
material, such as found in a neutron
star, for instance, might be required. Certainly, we don't have any of that, either!
[edit on 24 June 2010 by weedwhacker]