The Sharpness of Knives.

[DavidwithanR]

@whc.03grady

A knife is a type of wedge, if I remember my simple machines correctly.

In theory, sure, though of course in practice they are treated differently. Wedges take positive advantage of characteristics that would cause poor knife performance.

(The words even show it - if you get your knife “wedged” in the material you’re cutting, something has probably gone wrong.)

[Whack-a-Mole]

@Shodan

The word “atom” comes from the Greek word atomos, which means “uncuttable”.

Indeed but I am willing to bet you know that ancient Greeks weren’t really up on their physics and did not know there are smaller things than atoms.

As to the OP I think it has been covered here but I will add a molecule thick cutting surface is not likely to last long. Since it is so thin it will start to abrade away almost as soon as you start cutting.

But yeah…for that first cut it will be mighty sharp but that single molecule thickness will disappear almost as soon as you start cutting. It will remain mighty sharp for a bit but it will probably dull quickly to more “normal” sharpness (which is still sharp).

[AHunter3]

@whc.03grady

@AHunter3

In practice, a sharp knife is a knife with a very thin edge, the thickness of which increases very slowly as you move to the back (otherwise it’s a wedge not a knife)

A knife is a type of wedge, if I remember my simple machines correctly.

I think you’re being pedantic.

• checks forum *

Umm, not that there’s anything wrong with that.

[Leo_Bloom]

[bob_2]

Death’s scythe is one of the two sharpest objects in existence. It is capable of slicing air, shadows and even time. Most importantly, it is designed to sever souls from their mortal shells. The blade is almost transparent, but glows blue thanks to the energy released by atoms splitting on its edge (thanks to the idiosyncrasies of Discworld physics, this does not cause the nuclear obliteration of a vast area).

In Reaper Man, thinking he might fight back against the New Death, Death sharpens a scythe blade. First on a grindstone, then on an oilstone, then on a steel. It was too blunt. Miss Flitworth supplied, from her rag bag, satin, then silk, finest white silk, never worn (from her wedding dress). It was still blunt. Then it was sharpened on cobweb. Then on the breeze at dawn.

[Chronos]

Nitpick: On the midnight breeze, and then on the first light of dawn.

Af/ /ter tha/ /t, it was sh/ /arp eno/ /ugh.

[Shodan]

in the Volsunga Saga, Sigurd’s sword Gram was tested first by cutting an anvil in half, then by throwing wool upstream and dipping the sword into the stream and letting the wool drift down and be cut by the edge. Cite.

I sympathize with Regin the dwarf smith, but that’s what you get when you let the users write the specs document.

Regards,
Shodan

[jtur88]

What started my BS flag flapping was the conditions of the find itself. If it ever had an edge of one molecule dimension, what are the chances that it would remain intact through thousands of years of exposure to the environment? The more so, when it is fashioned of organic composition. Although, a diamond is also organic, so that may not be germane.

[Ashtura]

Many surgeons use obsidian scalpels. They’re demonstrably sharper than steel scalpels.
If there were something sharper than that, I’d imagine they’d use them.

[gnoitall]

@Shodan

in the Volsunga Saga, Sigurd’s sword Gram was tested first by cutting an anvil in half, then by throwing wool upstream and dipping the sword into the stream and letting the wool drift down and be cut by the edge. Cite.

I need to read the Volsunga Saga. That story brings to mind the Japanese equivalent, the contest between the legendary swordsmiths Masamune and Muramasa:

@Wikipedia

A legend tells of a test where Muramasa challenged his master, Masamune, to see who could make a finer sword. They both worked tirelessly and eventually, when both swords were finished, they decided to test the results. The contest was for each to suspend the blades in a small creek with the cutting edge facing the current. Muramasa’s sword, the Juuchi Yosamu (十千夜寒, “10,000 Cold Nights”) cut everything that passed its way; fish, leaves floating down the river, the very air which blew on it. Highly impressed with his pupil’s work, Masamune lowered his sword, the Yawarakai-Te (柔らかい手, “Tender Hands”), into the current and waited patiently. Only leaves were cut. However, the fish swam right up to it, and the air hissed as it gently blew by the blade. After a while, Muramasa began to scoff at his master for his apparent lack of skill in the making of his sword. Smiling to himself, Masamune pulled up his sword, dried it, and sheathed it. All the while, Muramasa was heckling him for his sword’s inability to cut anything. A monk, who had been watching the whole ordeal, walked over and bowed low to the two sword masters. He then began to explain what he had seen.
“The first of the swords was by all accounts a fine sword, however it is a blood thirsty, evil blade, as it does not discriminate as to who or what it will cut. It may just as well be cutting down butterflies as severing heads. The second was by far the finer of the two, as it does not needlessly cut that which is innocent and undeserving.”

ETA: Of course, this is just a legend; the two swordsmiths weren’t even contemporaries (about 300 years separated them, which is a little time in Japanese history). But that’s the legend, incorporating the cultural memes associated with the two foremost swordsmiths in Japanese history: Masamune made holy swords, and Muramasa made evil and blood-thirst swords.

[Chronos]

I’ve also heard a version of that story where Masamune’s blade didn’t even cut the leaves, but parted the water around it so that there would be no unnecessary destruction at all.