| lwcamp |
08-07-2010 11:16 AM |
Re: Planet cracker
Quote:
Originally Posted by lexington
(Post 1028729)
lol, okay I see. I suppose I can jus e-mail him and find out where the numbers came from.
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Oh, you were being serious. In that case, the values for boiling or evaporating the oceans likely come from knowing the mass of the ocean and the specific heat and heat of vaporization of water. It takes 4180 J to raise the temperature of 1 kg of water by 1 degree C. So if the average temperature of the ocean is 10 C, for example, then for every kg of ocean water it takes (100 C - 10 C) * 4180 J to raise it to boiling. Once you have it at boiling temperature, it takes 2,257,000 J/kg to boil the water into steam. This is assuming the water is pure - salt and other stuff will affect these values a bit, but not by all that much.
The rest probably comes from knowing the mass of the atmosphere, oceans, and crust and figuring the work needed to take than mass from the planets surface to far enough away that it is no longer under the influence of the earth's gravity. Since the escape velocity on earth is 11.2 km/s, 1 kg of mass shot off the earth with enough speed to escape from the earth would have a kinetic energy of 63 MJ. This gives the energy per kilogram needed to gravitationally unbind something from our planet - assuming you are not lifting so much off the planet that the mass of the planet significantly changes. So multiply the mass of the oceans in kg by 63 MJ to get the energy to blast all the oceans on earth off the planet so hard they will not come back.
Luke |