# Indestructible sword blade with a .30 micron cutting edge…how destructive, exactly? **URL:** \ **Category:** Factual Questions\ **Created:** [August 19, 2013, 8:52am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623 "2013-08-19T08:52:43Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [August 19, 2013, 8:52am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/1 "2013-08-19T08:52:43Z")
Something I’ve been mulling over for awhile. Mostly from whenever Hugh Jackman’s in a movie or tv show. Anyway— You, an average sized north american adult male, have a sword, patterned after the [M1917/41 cutlass](http://www.thepirateslair.com/9-m1917-us-navy-naval-cutlass.html)\*, but with an Adamantium blade. It is thus, while almost identical in density and flexibility to steel, completely indestructible. And has a cutting edge sharpened to .30 microns. (Which, I understand, is a _somewhat_ reasonable figure for a frighteningly sharp metal blade.) So, how much damage COULD the average person actually do with this thing? What would happen if you tried and hack through a person—or an I-beam, or the frontal armor of an M1 Abrams? \*Design chosen entirely because Katanas are overexposed. Better weapon suggestions are cheerfully welcomed. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [August 19, 2013, 9:48am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/2 "2013-08-19T09:48:24Z")
> [@Ranchoth](#): > > So, how much damage COULD the average person actually do with this thing? What would happen if you tried and hack through a person—or an I-beam, or the frontal armor of an M1 Abrams? Not much. Blades don’t stop cutting mid-swing because they become blunt. They stop cutting because of friction/resistance from whatever they are being pushed through. Whether the blade becomes blunt or not won’t have much effect on that. You can see this yourself when cutting wood with an axe. Even though wood won’t blunt an axe much in one blow, the axe still won’t go in more than a few inches. Hitting metal or flesh with your sword will have about the same effect regardless of whether the sword is made of adamantium or stainless steel. The only advantage of such a blade is that it will be able to keep doing this again and again. But the amount of damage done with a fresh stainless blade and your adamantium blade won’t be readily distinguishable. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [August 19, 2013, 10:15am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/3 "2013-08-19T10:15:39Z")
What if the blade were frictionless? ---
**Author:** ![moriah](https://avatars.discourse-cdn.com/v4/letter/m/b2d939/32.png) [@moriah](https://boards.straightdope.com/u/moriah)\ **Post date:** [August 19, 2013, 11:52am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/4 "2013-08-19T11:52:33Z")
While the cutting edge may be very small, the rest of the blade isn’t. A chopping slice needs to open up a gash in the object being cut large enough for the rest of the blade to fit through. Several inches of steel as part of a multi-ton object isn’t going to peel open like an orange rind. And being ‘frictionless’ isn’t going to help. If you’re sliding on a floor that is frictionless, you’ll come to a full stop when you hit a wall. A frictionless blade is hitting two ‘walls’ at an angle… in other words, a corner. Corners stop frictionless sliders as well as walls. ---
**Author:** ![Chimera](https://avatars.discourse-cdn.com/v4/letter/c/8e8cbc/32.png) [@Chimera](https://boards.straightdope.com/u/Chimera)\ **Post date:** [August 19, 2013, 3:01pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/5 "2013-08-19T15:01:38Z")
How the heck would you sharpen an indestructible sword? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 19, 2013, 3:51pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/6 "2013-08-19T15:51:18Z")
You make it sharp to begin with, and then you rely on its indestructibility keeping it sharp so you never have to sharpen it again. But then, if you have a truly indestructible metal to begin with, why make it blade-shaped? Just make a single wire with that diameter, maybe with a plastic bead stuck on the end so you can see where it is. ---
**Author:** ![Chimera](https://avatars.discourse-cdn.com/v4/letter/c/8e8cbc/32.png) [@Chimera](https://boards.straightdope.com/u/Chimera)\ **Post date:** [August 19, 2013, 3:54pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/7 "2013-08-19T15:54:55Z")
Well that’s what I would think, but the OP said “sharpened to”. ---
**Author:** ![iiandyiiii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iiandyiiii/32/7924_2.png) [@iiandyiiii](https://boards.straightdope.com/u/iiandyiiii)\ **Post date:** [August 19, 2013, 3:55pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/8 "2013-08-19T15:55:07Z")
> [@Chimera](#): > > How the heck would you sharpen an indestructible sword? You wouldn’t have to, right? ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [August 19, 2013, 3:57pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/9 "2013-08-19T15:57:14Z")
Why not make the whole blade .30 microns thick instead of just the cutting edge? ---
**Author:** ![Cartoonacy](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@Cartoonacy](https://boards.straightdope.com/u/Cartoonacy)\ **Post date:** [August 19, 2013, 4:01pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/10 "2013-08-19T16:01:01Z")
That sounds like the [Variable Swords](http://larryniven.wikia.com/wiki/Variable_sword) from Larry Niven’s “Known Space” novels: a filament one molecule wide, held rigid by a stasis field generated in the hilt, with a bead on the tip so the user can see where it ends. ---
**Author:** ![Snarky\_Kong](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@Snarky\_Kong](https://boards.straightdope.com/u/Snarky_Kong)\ **Post date:** [August 19, 2013, 4:09pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/11 "2013-08-19T16:09:23Z")
> [@Chronos](#): > > You make it sharp to begin with, and then you rely on its indestructibility keeping it sharp so you never have to sharpen it again. > > But then, if you have a truly indestructible metal to begin with, why make it blade-shaped? Just make a single wire with that diameter, maybe with a plastic bead stuck on the end so you can see where it is. The OP specifies that it’s as flexible as steel. ---
**Author:** ![Darth\_Panda](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Darth\_Panda](https://boards.straightdope.com/u/Darth_Panda)\ **Post date:** [August 19, 2013, 5:02pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/12 "2013-08-19T17:02:12Z")
> [@Chimera](#): > > How the heck would you sharpen an indestructible sword? Unstoppable whetstone. ---
**Author:** ![AdamF](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/adamf/32/6246_2.png) [@AdamF](https://boards.straightdope.com/u/AdamF)\ **Post date:** [August 19, 2013, 7:31pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/13 "2013-08-19T19:31:59Z")
> [@Cartoonacy](#): > > That sounds like the [Variable Swords](http://larryniven.wikia.com/wiki/Variable_sword) from Larry Niven’s “Known Space” novels: a filament one molecule wide, held rigid by a stasis field generated in the hilt, with a bead on the tip so the user can see where it ends. Such blade wouldn’t make a very good sword. It would be something like [nuclear shears](http://www.technovelgy.com/ct/content.asp?Bnum=2353) in Asimov’s Foundation. > [@](#): > > “Bring two short lengths of pipe, somebody.” Mallow stood them upright and shaved the ends off with a single stroke of the shear, and then joined the pipes, fresh cut to fresh cut. And there was a single pipe! The new ends, with even atomic irregularities missing, formed one piece upon joining. Mallow talked through and around his thoughts, “Test that pipe! It’s one piece. Not perfect; naturally, the joining shouldn’t be done by hand.” ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [August 19, 2013, 9:08pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/14 "2013-08-19T21:08:10Z")
> [@AdamF](#): > > Such blade wouldn’t make a very good sword. It would be something like [nuclear shears](http://www.technovelgy.com/ct/content.asp?Bnum=2353) in Asimov’s Foundation. Well, to be perfectly fair, Niven’s underlying technology (monomolecular filament, aka Sinclair Molecule Chain) wasn’t strictly for weaponry, although in his rather dramatic stories that’s the main use you see. But it makes a supremely good sword, assuming the existence of stais fields to hold the otherwise super-flexible blade rigid. See also Herbert’s “shigawire”, Brunner’s “General Technics monofilament”, or Willam Gibson’s ninja wire weapon from “Johnny Mnemonic”. Also the relevant [TVTropes page](http://tvtropes.org/pmwiki/pmwiki.php/Main/SharpenedToASingleAtom). ---
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [August 20, 2013, 4:52am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/15 "2013-08-20T04:52:37Z")
> [@Chimera](#): > > Well that’s what I would think, but the OP said “sharpened to”. My bad—it simply seemed a (slightly) more elegant turn of phrase than “forged to” or “fabricated to a cutting edge of…” On that note, how WOULD the performance change if the entire blade was only .30 microns thick? ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [August 20, 2013, 7:20am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/16 "2013-08-20T07:20:26Z")
I’m reminded of DEATH honing his scythe in PTerry’s “Reaper Man”. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [August 20, 2013, 12:26pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/17 "2013-08-20T12:26:46Z")
[QUOTE=Ranchoth;16587731On that note, how WOULD the performance change if the entire blade was only .30 microns thick?[/QUOTE] Well, if it was ‘as flexible as steel’, I don’t think you’d get much cutting done. You’d have a wire bending almost as soon as you pressed it against something (probably a very shallow cut in whatever it was pressed against, but I don’t think it would go very far before meeting enough resistance to bend). ---
**Author:** ![AdamF](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/adamf/32/6246_2.png) [@AdamF](https://boards.straightdope.com/u/AdamF)\ **Post date:** [August 20, 2013, 2:07pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/18 "2013-08-20T14:07:32Z")
> [@gnoitall](#): > > Well, to be perfectly fair, Niven’s underlying technology (monomolecular filament, aka Sinclair Molecule Chain) wasn’t strictly for weaponry, although in his rather dramatic stories that’s the main use you see. But it makes a supremely good sword, assuming the existence of stais fields to hold the otherwise super-flexible blade rigid. The whole idea behind monomolecular blade is that it is so thin, it can slip between atoms of material and meet no resistance. But as Asimov pointed out, when you have two perfectly smooth surface within a few atom diameters of each, they’ll stick back together as if they were a single block. I can see a monomolecular blade passing though a block of steel leaving no trace of its passing. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 20, 2013, 3:08pm UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/19 "2013-08-20T15:08:15Z")
“Monomolecular” is a bit of a red herring, anyway. We’ve all used monomolecular cords (and a wide variety of other useful objects), and most of us have never been cut by them. It’s not enough to make a cord out of a single molecule-- What you want is to make it out of a single _really skinny_ molecule. ---
**Author:** ![mandala](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mandala/32/95_2.png) [@mandala](https://boards.straightdope.com/u/mandala)\ **Post date:** [August 21, 2013, 12:22am UTC](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623/20 "2013-08-21T00:22:06Z")
Monomolecular swords / cords are not going to do much cutting. When you cut an object, say firewood, with a blade, the cutting edge of the blade physically pushes away molecules to either side of the impact area, or ejects the molecules altogether (as sawdust). Cutting does not destroy chemical bonds within the object - it merely physically displaces the molecules, so they no longer contribute to the structural strength of the object being cut. Displace enough of such molecules, and you have sliced the object completely. With a blade so thin it’s only a molecule wide, you’d have to be incredibly lucky to have those cutting-edge molecules hit anything at all in the object being cut. Most of any object (even seemingly dense objects such as iron) is empty space. Molecules are mostly empty space too. When you swing a monomolceular blade at a ball of iron, chances are the blade will emerge through the sphere having not touched a single iron atom. If you had a monomolecular blade made of ultradense matter - such as the hypothetical neutronium - then you _might_ achieve a clean cut in one attempt. Still, even assuming the blade displaces all molecules in the object in a swath one molecule wide, I am not sure it will completely destroy the object’s structural integrity in that area. Most real-life objects have a choatic internal arrangement of atoms and molecules and their structural integrity at any point is not just ‘one molecule thick’. Surrounding molecules contribute to the strength, too, and they are not going to be hit by your ultrathin blade. Swinging another cut is useless too, as you will merely hit the object again in another area, causing another ‘cut’ but not disrupting the object completely. So there is a limit to ‘sharpness’ - your blade must be very sharp to minimize friction, but wide enough to cause enough damage to ‘cut’ the object and disrupt it. Monomolecular blades are not upto the job. I am not a physicist or a chemist so I’d not be surprised to learn I was completely wrong here. [Next page](https://boards.straightdope.com/t/indestructible-sword-blade-with-a-30-micron-cutting-edge-how-destructive-exactly/666623.md?page=2)