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atorm comments on Harry Potter and the Methods of Rationality discussion thread, part 28, chapter 99-101 - Less Wrong Discussion

7 Post author: palladias 12 December 2013 05:10AM

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Comment author: TobyBartels 12 December 2013 02:55:33PM 1 point [-]

an overlarge metal blade whose edge did not gleam beneath the moonlight; a gleaming edge, Harry had once read, was the sign of a dull blade

Of course, the real reason that it's not gleaming is that Eliezer once read that!

Comment author: atorm 13 December 2013 02:32:28PM 5 points [-]

I would like to know where he read it.

Comment author: RichardKennaway 13 December 2013 07:14:25PM 3 points [-]

I have also read it, I don't remember where. It's not a particularly outré piece of knowledge, just a piece of knife-sharpening lore. The reason a properly sharpened blade does not show a visible edge is that the edge is thinner than the wavelength of light.

I do not know if this is true, which puts me in much the same position as Harry. It's just something I've read but never put to practical test.

Comment author: linkhyrule5 14 December 2013 01:19:36AM 2 points [-]

As an owner of a penknife that I occasionally sharpen: It is definitely true that a dull blade gleams, but I am not sure if it is true that a sharp blade does not.

Comment author: jimmy 18 December 2013 04:55:27AM 2 points [-]

Sharp edges don't reflect any light visible to the naked eye, but it'll show up on an illuminated microscope.

The edge width is on par with the wavelength of light at ~300-500 nanometers at best

Comment author: TobyBartels 15 December 2013 05:57:20AM 0 points [-]

Harry, or Eliezer? :-P