# the most possible degree of sharp? **URL:** \ **Category:** Factual Questions\ **Created:** [October 29, 2004, 4:55pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873 "2004-10-29T16:55:22Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![merovingian](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@merovingian](https://boards.straightdope.com/u/merovingian)\ **Post date:** [October 29, 2004, 4:55pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/1 "2004-10-29T16:55:22Z")
If anyone has seen the movie “the bodyguard” starring Whitney Houston and Kevin Costner, there is a scene where Whitney’s silk handkercheif drops, and as it falls, comes in contact with a Samurai sword. As it continues downward, it is cut in half effortlessly. Have we been duped by yet another Hollywood special effect, or is this degree of “sharpness” acheivable, and if so, how? Laser honed? special procedure involving a series of whetstones? ---
**Author:** ![Chairman\_Pow](https://avatars.discourse-cdn.com/v4/letter/c/838e76/32.png) [@Chairman\_Pow](https://boards.straightdope.com/u/Chairman_Pow)\ **Post date:** [October 29, 2004, 5:11pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/2 "2004-10-29T17:11:05Z")
Here’s a thread on “[were swords sharp](http://boards.straightdope.com/sdmb/showthread.php?t=274913&highlight=sharp+medieval+swords)” that might have some useful information. From that discussion, there’s a tradeoff between how “Sharp” something is and how durable the blade is. Of course, with modern technology, that may likely be irrelevant to some degree. Read down the thread for the discussion of Saladin’s sword and the pillow. Also, “[how does a knife cut on a molecular level](http://boards.straightdope.com/sdmb/showthread.php?t=253010&highlight=knife+molecular).” ---
**Author:** ![merovingian](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@merovingian](https://boards.straightdope.com/u/merovingian)\ **Post date:** [October 29, 2004, 8:23pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/3 "2004-10-29T20:23:24Z")
is there a way of determining the degree of sharpness? is there a univeral standard measurement? if so, what is considered to be the sharpest edge known to man? ---
**Author:** ![alterego](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@alterego](https://boards.straightdope.com/u/alterego)\ **Post date:** [October 29, 2004, 8:33pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/4 "2004-10-29T20:33:46Z")
Just WAGging my tail, but I think the highest degree of sharpness would be attained by taking a material one atom thick, and laying on top of it and under it another layer one atom thick, where the pits of the first layer were filled by the pits of the second layer, and indenting it back one atom each time. It also seems to me that sharpness is relative to the hardness of the knife and the softness of the object being cut. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [October 29, 2004, 8:49pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/5 "2004-10-29T20:49:43Z")
Duped, big time. A properly stropped straight razor won’t do that so I’m quite certain that no one has done it with a sword, even if they sharpened it to such a narrow angle which would be ridiculously fragile. I have a nice hat to eat if anyone can show me otherwise. Sharpness is a tricky thing. You can easily make a knife shaving sharp but with a wide enough edge angle to have some durability. It will shave but the cut won’t be effortless. An ultra narrow angle as on a hollow ground straight razor will cut more effortlessly but won’t hold that edge as long. That’s why the barber touches up the edge with a roughed strop before every shave and sometimes during. ---
**Author:** ![merovingian](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@merovingian](https://boards.straightdope.com/u/merovingian)\ **Post date:** [October 29, 2004, 8:56pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/6 "2004-10-29T20:56:14Z")
Are surgical scapels then, the sharpest objects known to man? ---
**Author:** ![merovingian](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@merovingian](https://boards.straightdope.com/u/merovingian)\ **Post date:** [October 29, 2004, 8:56pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/7 "2004-10-29T20:56:56Z")
Are surgical scapels perhaps, the sharpest objects known to man? ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [October 29, 2004, 9:14pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/8 "2004-10-29T21:14:52Z")
[BLADES AND CORES OF OBSIDIAN](http://www.ambergriscaye.com/museum/digit1.html) > [@](#): > > Widely used throughout the western hemisphere and the rest of the world as well) obsidian blades, when freshly struck from the core represent the sharpest cutting edge known, several times sharper than a surgical steel scalpel. In fact obsidian blades are currently in use in some U.S. hospitals for heart bypass surgery. It seems that they cut cleaner, thereby promoting more rapid healing with less scar tissue ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 29, 2004, 11:14pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/9 "2004-10-29T23:14:05Z")
> [@merovingian](#): > > Are surgical scapels perhaps, the sharpest objects known to man? I’d say that the electron knives used in creating the masks for IC chips are much ‘sharper’ than this, given that they are working on microscopicly narrow circuit paths. Not sure if you would count them as an “object” though, as the working part is more an electromagnetic field than a physical item. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [October 30, 2004, 12:17am UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/10 "2004-10-30T00:17:43Z")
> [@](#): > > Are surgical scapels perhaps, the sharpest objects known to man? Of course not! Don’t you remember those commercials about six months ago for some razor that was made out of “titanium, the sharpest metal known to man!”? :rolleyes: ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [October 30, 2004, 12:26am UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/11 "2004-10-30T00:26:05Z")
I’ll second the claim for obsidian being the sharpest. The edge of an obsidian blade can supposedly get to a thickness of a molecule. And, I can tell you from personal experience that a freshly excavated 1500+ year old obsidian blade can draw blood easily. ---
**Author:** ![alterego](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@alterego](https://boards.straightdope.com/u/alterego)\ **Post date:** [October 30, 2004, 12:30am UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/12 "2004-10-30T00:30:57Z")
I don’t see why synthetically fabricated carbon nanotubes could not be made sharper than obsidian. [Harder than diamond as well…](http://slashdot.org/article.pl?sid=04/10/08/1931236) ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [October 30, 2004, 12:33am UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/13 "2004-10-30T00:33:06Z")
> [@alterego](#): > > I don’t see why synthetically fabricated carbon nanotubes could not be made sharper than obsidian. [Harder than diamond as well…](http://slashdot.org/article.pl?sid=04/10/08/1931236) Why bother with the time and expense to create something in a lab when all you need is some practice with knapping? ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [October 30, 2004, 12:55am UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/14 "2004-10-30T00:55:42Z")
I believe the sharpest man-made objects are the ultramicrotomes used to make specimen slices for electron microscope viewing. They can slice a _virus_ in half! ---
**Author:** ![merovingian](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@merovingian](https://boards.straightdope.com/u/merovingian)\ **Post date:** [October 30, 2004, 1:26pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/15 "2004-10-30T13:26:46Z")
> [@Lumpy](#): > > I believe the sharpest man-made objects are the ultramicrotomes used to make specimen slices for electron microscope viewing. They can slice a _virus_ in half! OMG! I had no idea! how are the ultramicrotomes made? are they synthetic or naturally occuring? ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [October 30, 2004, 1:44pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/16 "2004-10-30T13:44:12Z")
I think, to answer the OP, that you ought to think about the question in a aslightly different way: cutting anything requires breaking molecular bonds, which requires energy to do. So whether your silk handkerchief will be sliced depends on how much kinetic energy exists in the falling handkerchief versus how much is needed to slice the fabric. Now, I’m not sure how to calculate energy required to break molecular bonds, but my point here is that this value is not zero, and will never be zero, no matter how “sharp” your blade is. So there must be _some_ object that is so small that it never obtains enough energy, when dropped in the air, to slice itself through. I can’t prove that a handkerchief fits in that category, but my intuition says that it would. ---
**Author:** ![merovingian](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@merovingian](https://boards.straightdope.com/u/merovingian)\ **Post date:** [October 30, 2004, 1:48pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/17 "2004-10-30T13:48:49Z")
> [@zut](#): > > I think, to answer the OP, that you ought to think about the question in a aslightly different way: cutting anything requires breaking molecular bonds, which requires energy to do. So whether your silk handkerchief will be sliced depends on how much kinetic energy exists in the falling handkerchief versus how much is needed to slice the fabric. > > Now, I’m not sure how to calculate energy required to break molecular bonds, but my point here is that this value is not zero, and will never be zero, no matter how “sharp” your blade is. So there must be _some_ object that is so small that it never obtains enough energy, when dropped in the air, to slice itself through. > > I can’t prove that a handkerchief fits in that category, but my intuition says that it would. Yes, but aerodynamics absent from the equation, the silk handkerchief will drop at the same rate as a brick. 😃 ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [October 30, 2004, 3:27pm UTC](https://boards.straightdope.com/t/the-most-possible-degree-of-sharp/271873/18 "2004-10-30T15:27:48Z")
> [@merovingian](#): > > Yes, but aerodynamics absent from the equation, the silk handkerchief will drop at the same rate as a brick. 😃 A moot point as you could accomplish the same thing by making the scarf longer so there was more weight to provide force against the cutting edge. The OP asked about sharpness in a very specific circumstance. I’ve heard people claim that swords can be so sharp but never never seen anything to back that up.