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Bakkot comments on Harry Potter and the Methods of Rationality discussion thread, part 20, chapter 90 - Less Wrong Discussion

9 Post author: palladias 02 July 2013 02:13AM

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Comment author: Bakkot 02 July 2013 05:00:15AM *  -1 points [-]

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Comment author: [deleted] 02 July 2013 06:09:47AM 13 points [-]

Actually, the process in stars is fusion. The same as modern atom bombs, too.

Fission is used in nuclear power plants, and only really used to reach the conditions for fusion in bombs.

Comment author: Protagoras 02 July 2013 08:21:36AM 10 points [-]

Actually, most nuclear weapons get roughly comparable amounts of their force from fission and fusion, usually a little more from fission. Fission-only bombs are so much less powerful not because fission is but because they have very incomplete fission (around 1% for the Hiroshima bomb design, for example). The fusion reactions used in bombs produce a lot of excess neutrons, by design; all those neutrons flying around mean a lot more fission ends up happening. The only bombs that get most of their power from fusion are neutron bombs (which use a lot less fissionable material, and use the excess neutrons to increase the radiation damage) and clean bombs (which also use a lot less fissionable material, but replace it with lead to absorb the excess neutrons; clean is of course a relative term here).

Comment author: Alsadius 02 July 2013 05:36:46PM 0 points [-]

The biggest difference as regards fission is that fusion bombs use U-238 as a power source, which is capable of releasing energy from fission, but which doesn't produce enough neutrons to sustain a chain reaction. But when fed excess neutrons from a fusion reaction, you get an immense energy release from a very cheap material that's used as the bomb casing.

Comment author: buybuydandavis 02 July 2013 08:34:33AM *  6 points [-]

Also harkens back to:

“Hm,” Harry said. “Suppose you threw it into the Sun? Would it be destroyed?”
...
“It seems unlikely, Mr. Potter,” Professor Quirrell said dryly. “The Sun is very large, after all; I doubt the Dementor would have much effect on it. But it is not a test I would like to try, Mr. Potter, just in case.”

Also, on Quirrell's particular attitude toward the sun:

Harry had lost. There had been moments when the cold anger had faded entirely, replaced by fear, and during those moments he’d begged the older Slytherins and he’d meant it...
“Is the Sun still in the sky?” said Professor Quirrell, still with that strange gentleness. “Is it still shining? Are you still alive?

Harry lost, and Quirrell's is basically asking "was it the end of the world to lose?"

Comment author: linkhyrule5 02 July 2013 06:05:30AM 2 points [-]

Or material. Stars are great sources of raw matter, if you can get at it safely.

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