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Comment Re:ZERO? (Score 1) 170

If you have Maple handy, this one-liner does the trick:

a := whatever; b := 2; while not(isprime(a-b)) do b := nextprime(b) end do; a-b, b;

Of course the interesting part is the code for isprime(). You can start here if you want to know how it's done.

Comment Re:Impossible (Score 1) 637

Let's define "the surface of the earth" by the first meter of atmosphere, and let's see by how much we could warm that much air.

Air has a heat capacity of .001297 J/cm^3/K, that is 1.3e3 J/m^3/K. (source)
Earth has an area of 510 million square kilometers, that is 5.1e14 m^2. (source)
Total nuclear arsenal is roughly 5 gigatons of TNT, that is 5 times 4.184e18 J or 2.6e19 J (source)
So, we could warm one meter of atmosphere by (2.6e19 / (1.3e3 * 5.1e14)) K or about 40 K.

Not enough to kill anything but the lamest creatures but to be honest, I expected much much less than that. Of course, that's assuming all the energy goes into heating a layer of air covering the globe, which isn't what would happen but still, 40 K over the whole world, holy shit.

Comment Re:Wouldn't a giant impact change its orbit? (Score 1) 257

Why the Giant Impactor Theory assumes a different isotope mix for the impactor?

From what I understand, they had to have rocks brought back from the Moon to actually measure their isotope mix, so my guess is that we don't accurately know the isotope mix of anything besides the Earth and the Moon. How do we know it isn't the same mix everywhere in the solar system?

Disclaimer: I'm clueless about all this, I'm only asking questions.

Comment Re:Its Not An Energy Problem, Transportation Fuels (Score 1) 835

If you solve the energy problem (ie, you can produce eco-friendly electricity cheaply enough), you can make pretty much any hydrocarbons you want out of CO2, water and electricity. Efficiency won't be perfect (or even good), but if your electricity generation is eco-friendly and abundant enough that's not a problem.

Maybe batteries/capacitors/whatever will improve enough so that we won't need to do that but if they don't, it won't necessarily mean the end of cheap transportation.

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