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The Year In Ideas
popo writes "The New York Times Magazine has a review of the year's most original and interesting ideas. They include "The Tornado in a Can" ("A contained cyclone, it turns out, is very useful for pulverizing things") and David Stevenson's real-life proposal to dig to the center of the Earth. by sinking heavy iron through the Earth's mantle."
Speaking of top ideas, check out SlipHead.com. Its an open forum for the free exhange of ideas - similar to the way the open software movement works. Get recognized for having the best ideas, and who knows, maybe you'll even catch the eye of an investor!
Yes, water weighs 8.34 lb/gal. That means ~240 gallons of water would be in the two tons of trash. 240 gallons of water is ~32 ft^3. While I do believe I overlooked the water loss, I don't believe it could be all water.
It's sort of neat to see a story like this, because Dr. Stevenson was one of my advisors at Caltech. He's a great guy with a cool New Zealand accent and a wide assortment of knowledge about almost everything. But I can shed a little light on this, both because I know him and because I have a geology background.
First, for the credulous, he's semi-joking. The physics of the iron sinking into the core is actually plausible, but his tone when talking about "generating a crack in the crust" is tongue-in-cheek. This would require a much larger nuclear detonation, say, than has ever been tested by anybody. The seismic consequences would be... bad. What's more, we aren't anywhere even close to being able to design probes that could survive such an environment and send messages back.
To dispel a common misconception, the interior of the earth is NOT molten. Omitting some interesting boundary layers, the Earth is composed of the following chunks from the inside out: the inner core (solid iron alloy), the outer core (molten iron alloy), the mantle (solid rock), and the crust (we live on it). If you're curious as to how we know, it's because liquids and solids have dramatically different properties as far as transmitting seismic waves. I just found a decent site at JPL here that illustrates the earth's structure nicely, although it appears to have been written for grade schoolers.
The idea that the mantle is liquid is one of the most widely held misconceptions about major geological concepts. It exhibits ductile deformation, so it flows something like a liquid, with a speed of centimeters or meters per year. Magma, however, results when rock is pushed up into the crust from the mantle - the decrease in pressure lowers the melting temperature. It can also be generated when water seeps into hot rocks - wet rock has a lower melting temperature. It is NOT evidence that the mantle itself is liquid.
So why would this work? A large body of iron would be much denser than mantle rock, and at a hundred million kilograms, the net downward force would be considerable enough to force mantle rock out of the way. I'm too lazy to figure out the physics for this post, but I would imagine this is the content of the Nature article. The interesting question would be, "would ductile deformation occur quickly enough to get the iron down in a reasonable amount of time?" The answer, apparently, is 'yes'.