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26th February 2007, 03:01 PM
This week's Commentary, at http://www.randi.org/jr/2007-02/022307sniffex.html#i11, refers to "Advanced Planetary Explorations, LLC", a company that plans to mount an expedition to the North Pole so that they can find the alleged opening to the interior of our hollow (!) Earth.
It got me to thinking ... how do Hollow Earthers explain the bizarre gravity that their world-model requires?
As shown in Randi's encyclopedia entry for Hollow Earth theory (www.randi.org/encyclopedia/Hollow%20Earth%20theory.html), the center of gravity is inside the crust, thereby allowing people on the inside to walk on the inner surface just like we top-dwellers walk on the outer surface. There are three immedate problems with this:
1) Simple calculus shows, and experiments confirm, that the gravitational field inside a uniform hollow spherical shell is zero (0) at all points. A person "standing" on the inner surface would feel a certain gravitational attraction from the small amout of material under his feet, and an equally-strong gravitational attraction in the opposite direction from the large amout of material on the opposite side of the sphere way far away. Net gravitational attraction: zero.
2) Even for us outer-surface dwellers, there's the problem of the Earth's density. We know from experiment how much gravity 1 kg of matter will produce at a given distance, and from this, we can deduce (from the strangth of Earth's gravity) that the mass of the Earth is 5.9742×1024 kg. If all that mass is compacted into a spherical shell only 100 kilometers thick, this spherical shell would have to have an average density of 118,000 kg per cubit meter, or 118 grams per cubic centimeter. For comparison, the lead that they make bullets and lead weights out of is only 11.34 grams per cubic centimeter -- so the material out of which this hollow Earth is composed would, on average, be over ten times the density of solid lead!
3) The hollow Earthers could, in principle, claim that it is their "central sun" that contributes most of the gravitational mass to the Earth, and that the mass of the spherical shell is actually relatively small. (Perhaps this central sun is a small white dwarf.) But then we have to ask: what kind of miraculous scaffolding is holding up this spherical shell so that it doesn't collapse under its own weight? Dirt and rocks aren't nearly strong enough to accomplish this feat. Perhaps the shell is made of arenak (http://www.rogermwilcox.name/arenak.html) or something.
It got me to thinking ... how do Hollow Earthers explain the bizarre gravity that their world-model requires?
As shown in Randi's encyclopedia entry for Hollow Earth theory (www.randi.org/encyclopedia/Hollow%20Earth%20theory.html), the center of gravity is inside the crust, thereby allowing people on the inside to walk on the inner surface just like we top-dwellers walk on the outer surface. There are three immedate problems with this:
1) Simple calculus shows, and experiments confirm, that the gravitational field inside a uniform hollow spherical shell is zero (0) at all points. A person "standing" on the inner surface would feel a certain gravitational attraction from the small amout of material under his feet, and an equally-strong gravitational attraction in the opposite direction from the large amout of material on the opposite side of the sphere way far away. Net gravitational attraction: zero.
2) Even for us outer-surface dwellers, there's the problem of the Earth's density. We know from experiment how much gravity 1 kg of matter will produce at a given distance, and from this, we can deduce (from the strangth of Earth's gravity) that the mass of the Earth is 5.9742×1024 kg. If all that mass is compacted into a spherical shell only 100 kilometers thick, this spherical shell would have to have an average density of 118,000 kg per cubit meter, or 118 grams per cubic centimeter. For comparison, the lead that they make bullets and lead weights out of is only 11.34 grams per cubic centimeter -- so the material out of which this hollow Earth is composed would, on average, be over ten times the density of solid lead!
3) The hollow Earthers could, in principle, claim that it is their "central sun" that contributes most of the gravitational mass to the Earth, and that the mass of the spherical shell is actually relatively small. (Perhaps this central sun is a small white dwarf.) But then we have to ask: what kind of miraculous scaffolding is holding up this spherical shell so that it doesn't collapse under its own weight? Dirt and rocks aren't nearly strong enough to accomplish this feat. Perhaps the shell is made of arenak (http://www.rogermwilcox.name/arenak.html) or something.