Al Gore on Conan O'Brien's show the other day:
Conan: Now, what about … you talk in the book about geothermal energy …
Al: Yeah, yeah.
Conan: and that is, as I understand it, using the heat that's generated from the core of the earth …
Conan: … to create energy, and it sounds to me like an evil plan by Lex Luthor to defeat Superman. Can you, can you tell me, is this a viable solution, geothermal
Al: It definitely is, and it's a relatively new one. People think about geothermal energy — when they think about it at all — in terms of the hot water bubbling up in some places, but two kilometers or so down in most places there are these incredibly hot rocks, 'cause the interior of the earth is extremely hot, several million degrees, and the crust of the earth is hot …
[Reality] The geothermal gradient is usually quoted as 25–50 degrees Celsius per mile of depth in normal terrain (not, e.g., in the crater of Kilauea). Two kilometers down, therefore, (that's a mile and a quarter if you're not as science-y as Al) you'll have an average gain of 30–60 degrees — exploitable for things like home heating, though not hot enough to make a nice pot of tea. The temperature at the earth's core, 4,000 miles down, is usually quoted as 5,000 degrees Celsius, though these guys claim it's much less, while some contrarian geophysicists have posted claims up to 9,000 degrees. The temperature at the surface of the Sun is around 6,000 degrees Celsius, while at the center, where nuclear fusion is going on bigtime, things get up over 10 million degrees.
If the temperature anywhere inside the earth was "several million degrees," we'd be a star.11/17 07:03 PMShare