Talk:Ninja rocks

Physics
I'd like to see someone with some knowledge on the subject add a section to this entry explaining the physics behind how porcelain shards are able to silently break glass. Alvis 08:31, 19 February 2006 (UTC)
 * That would be good, but none of the sources I've found go into the mechanics. Melchoir 01:01, 20 February 2006 (UTC)
 * I'd just came to the talk page to ask the exact some thing... hmmm... well I probably am the one here with a degree in physics.... Mathmo 00:54, 16 April 2006 (UTC)


 * I see this is now an editorial concern. The East County News reported on a demonstration they witnessed by police: the burglar throws a handful of ninja rocks moderately hard against a car window, and they bounce off with a quiet rattling noise. The window is intact but has microscopic fractures. He then gently pushes the window in with a gloved hand. Since Wikipedia is not an instruction manual, I don't think we need to give the method in detail, but rest assured that it works. Melchoir 05:51, 24 July 2006 (UTC)


 * And this is just out in left field. One of those newspaper articles even had a picture in it. What were you expecting, a peer-reviewed journal article in Nature just to prove that the California Assembly and Supreme Court know what they're doing? There is no reliable source that justifies writing "some may identify as fear mongering"; it's your personal opinion, it's original research, it's unverified, and it has no place in a Wikipedia article. Melchoir 05:37, 30 July 2006 (UTC)

This issue is pending moderation. http://en.wikipedia.org/wiki/Wikipedia:Mediation_Cabal/Cases/_2006-07-30_Ninja_Rocks Alvis 06:21, 30 July 2006 (UTC)


 * Okay, but seriously, what more evidence can you ask for than a demonstration of the technique performed by police in front of journalists and photographers? If that doesn't back up the claims with physical evidence, what does? Melchoir 06:51, 30 July 2006 (UTC)

Anecdotal and OR but when I was a firefighter/paramedic and instructor at a college fire academy which also served as an area training center I found in a very limited experiment that throwing the metal part of sparkplugs to be more effective at breaking tempered windows than the shards which never worked for our one experiment on this rumor. I think I had three ceramic chunks cracked with a hand sledge against pavement which actually hit tempered windows 2 rear and one rear side window hits, we lost the other bits to misses, for no breaks and one break to a rear side window from a thrown metal plug bottom. These windows were later further abused and mostly left intact by firefighters hitting them with various pocket tools carried in their firefighter turnouts before demonstrating the effectiveness of a centerpunch. I pulled the plugs from a car we we were going to cut up for a class. On duty I carried a spring-loaded metal auto-centerpunch for making a drilling start dimple on metal, it had a hardened steel tip; a similar automatic centerpunch was also stored in the handle of the windshield saw tool carried on our rescue units, medic units, and engines. The spring-loaded centerpunch worked easily safely every time activated by hand pressure, while even whacking away a window with a brass or aluminum folding hose-spanner was hit or miss taking a few tries right at the edge and risking glass pebbles hitting occupants, and as I said the ceramic chunks never worked the one time I tried it, perhaps we didn't throw them fast enough. As for pushing on the 'ninja rock' micro pitted window story above, anyone who has cut glass will know that the pressure needs to come from the opposite side of the glass from where the scratch is made or it will not work, by this logic the 'ninja rocks' might pit a window but only an occupant of a locked car can push or knock and cause the window to shatter. Being OR my statements should have no bearing on the article but hopefully might lead someone in a position similar to my former instructor role to document and publish their results.79.177.28.128 (talk) 14:11, 7 September 2016 (UTC)

Mediation
Hi, I’m the volunteer mediator who has agreed to look at this case. I have some initial reactions to things so far, so I will put those out to get the discussion started. I spent a few minutes search but did not find any materials questioning ninja rocks online. Tsetna 15:07, 30 July 2006 (UTC)
 * I cannot verify the ECN story, but if the story included a description of the demonstration, it should count as a verifiable and reliable source.
 * Is there a reliable source for the view that ninja rocks don’t work or are not used in the manner described in the article? What Wikipedia is not warns us against using Wikipedia as a repository of opinions. The best way to do that is to exclude original research. To do that, we need a verifiable and reliable source. Tsetna 15:07, 30 July 2006 (UTC)


 * Well, there's this forum thread, in which the topic starter expresses disbelief over ninja rocks-- and I'll bet the "[Link only for Registered Members]" is us! Anyway, the responses seem positive; one of them even talks about the physics. Interestingly, the participants seem to know about techniques that I haven't found in more reliable sources: holding the ninja rocks in one's hand or using a slingshot. I guess the exact method isn't so important. Melchoir 19:16, 30 July 2006 (UTC)


 * I got an email from the admin at rougesci.org- thier link is to this article. To me the responses to that link seem to be little more than wild-ass guesses. The single media citation is a very small paper, in fact the article was written by its editor (who has since been replaced). I thought this dispute would be a simple matter of data-mining, but it is starting to appear to me that original research is necessary to say anything about ninja rocks with any real precisio, other than that they appear in the book in CA and WA.  I found some police reports mentioning them by name, and a WA State police training PowerPoint, but that is it.  Without using weasel words, there isn't much you can say about ninja rocks at all. I don't doubt they exist and work as described though. Adelord 03:16, 17 August 2006 (UTC)

OK. Alvis, do you want to chime in? Tsetna 23:30, 2 August 2006 (UTC)
 * Guess my work is done here, no more dispute. I will close the mediation case but keep an eye on these pages too. Tsetna 16:32, 5 August 2006 (UTC)
 * Okay, thanks for helping! Melchoir 17:03, 5 August 2006 (UTC)
 * Haven't checked this page since starting the mediation; I don't have any evidence or cites that this phenomenon doesn't occur as stated. Coming from a background in physics, this just doesn't make sense.  All this article is doing is regurgitating media claims, which I'm not about to take at face value.  Popular news media doesn't have a established track record for being the original documentation for phenomena like this.  I'm just asking for a higher standard for an encyclopedia than building an article about a physics topic solely on news reports.


 * The rogusci article only contains hearsay. Many of the statements there, like "They are ultra-hard ceramic, and harder than the glass, which fractures the outer skin. The tempering does the rest." used to explain it don't make sense. Steel is harder than glass, but there's still a sound when it smashes it.  We can't take these posts as legitimate scientific commentary. Alvis 04:34, 8 August 2006 (UTC)


 * Hi there! I re-opened the case so we can all discuss. From my understanding of Wikipedia’s policies and guidelines, anything in Wikipedia needs a reliable source that is verifiable. I understand your worry about the media not being a good source, but what do you make of the legal evidence from California and Washington? I seem to recall that ceramic can be harder than metal. Is that incorrect? Tsetna 20:16, 8 August 2006 (UTC)


 * Alvis, may I correct you slightly ? Different kinds of steel have different hardness.  From the WP article on Moh's scale of hardness: " a pocketknife 5.1; a knife blade, 5.5; window glass plate, 5.5; and a steel file, 6.5" Darkman101 (talk) 20:39, 3 April 2011 (UTC)

Possible explanation
I saw Ninja rocks on a television program once, they explained that it is because the glass has a negative or positive charge (can't remember which) and the ceramic has the opposite charge, so when forced together they react to each other and something has to give, which is the glass as its weaker than the ceramic.

Perhaps someone can do some research based on this information. Kurt wills 14:57, 3 May 2007 (UTC)


 * Neither glass nor ceramics have any overall charge Dav2008 22:57, 18 May 2007 (UTC)

Dave, this is not necessarily true. Friction against certain surfaces can strip/deposit electrons onto glass (hence the rubbing the glass rod with the duster experiment). Conceivably this may happen in the air to the ceramic in flight and the car in motion. I might add, however, that it seems to me an unlikely method of this phenomenon: 1.) Static charges tend to be very small, 2.) The possibility that this effect would not have been observed on a more regular basis with other materials seems unlikely, 3.) Static force would cause a deceleration as the particles approached the glass (assuming they were negatively charged) reducing the momentum.

Also it is worthy of note that the car will discharge naturally over time, and there is no evidence I have heard to suggest it only works with recently stopped cars.

Hence an initial hypothesis might be that the tiny pieces of rock become sufficiently charged in flight so that by the time they approach the neutral glass, their momentum increases enough to cause a fracture in the glass on impact. Y0ssarian 22:30, 4 Febuary 2008 (GMT)

It has nothing to to with electrical charges. Ninja rocks work by the fact that porcelain is harder on the Mohs scale than glass. The porcelain strikes the glass and makes a tiny scratch. As the initial pressure from the impact subsides, the scratch fissures into a crack. Because car glass is designed to break into small pieces when cracked, the entire window shatters instantly. Theoretically, any material harder than the window glass that can scratch it should make a suitable ninja rock. [User:annonymous] 3:39, 28 September 2014 (GMT) — Preceding unsigned comment added by 2602:306:CE3F:BB0:4D31:A1CF:A345:B5F8 (talk)

Testing of ninja rocks?
I'm really surprised this issue of how they work in practice was brought up over a year ago and still no one has simply tested it and been able to report back. Just go to a junkyard or abandoned building or somewhere you can break glass without much trouble and test the things out, then we'll know. —Preceding unsigned comment added by 149.31.44.113 (talk) 19:33, 1 October 2007 (UTC)


 * By the way, I just found this video which shows them being used and working. Reading the comments on the video are also interesting as many of them assert that they've seen it happen before as well.  There is one comment which claims the video is a fake, but most do not believe it to be so and give reports of it being used in a number of instances before.  —Preceding unsigned comment added by 149.31.44.113 (talk) 19:46, 1 October 2007 (UTC)

I know it works. My friend bet me $50 it wouldnt work about a year ago. Not only did he lose the $50 he also had to replace the passanger's window in his car. —Preceding unsigned comment added by 99.141.111.2 (talk) 16:19, 23 March 2008 (UTC)

Want proof? Here.
Hello there, unregistered member helping you out. I dislike editing actual articles, so one of you guys could do it?

THIS is the thing. At least open it so you understand what I'm saying. Glass is 6,5 and porcelain is somewhere between 5 and 6. So it's almost as hard as glass. Iron is 4, weaker than porcelain and even WEAKER than glass. Think about that! It's strange, but once you get it, it's simple. If you hit a window with a hammer, chances are it will break, but if you don't hit hard enough, it won't break. Trust me I've tried. If you hit it with porcelain, it's much more likely to shatter. If you hit it with a DIAMOND, then it will break VERY EASILY. Read the article I linked for info. For example, the hardest element with a 10 on the mohs hardness scale (diamond) is 4 times harder than an element that measures 9 (corundum); whereas a 4 on the scale is only about 10% harder than a 3. Since the Mohs' hardness scale is a relative scale and not an absolute scale, the numbers assigned to each element should be used for reference purposes only. Remember we are talking about porcelain, not clay here.

Car breakers use this because if you fail to break the window with a hammer it will make a very loud bang. You can't risk that. If the porcelain isn't thrown hard enough it just chips off making almost no sound at all. --91.154.52.137 (talk) 20:32, 27 June 2008 (UTC)


 * "Remember we are talking about porcelain" Wrong. Spark plugs are made from alumina ceramic; a very different material to porcelain and one which is not harder and stronger than both porcelain and glass. —Preceding unsigned comment added by 203.160.114.205 (talk) 23:29, 31 October 2008 (UTC)

The physics has nothing to do with hardness, charges or little green men. The principal is quite simple, the SHARDS act as a wedge. The 2 things that are needed is a large handful of shards with razor sharp edges, enough speed and the right angle.

Tempered auto safety glass is structually very weak compared to other glass, it it DESIGNED to shatter when hit with enough force. If you look at tempered safety glass under a microscope you would see very tiny factures arranged in a pattern. The weakest point is in the center area of the glass as it is not resting on any part of the vehicle. If your shards are sharp enough then all you need is enough speed and the right throwing angle. Just a single shard hitting one of the tiny factures at the right angle with enough speed with the sharp edge will cause a chain reaction that will shatter, not break through the glass (like a wegde does when splitting a log). This is why a handful of shards is needed to do the job and sometimes several attempts are needed.

There is a nice video on youtube from the LLUMAR company, they make a interior security laminate to prevent smash and grabs, that shows how the shard shatter a auto window.

Hope this explains it better to you all cheers!! —Preceding unsigned comment added by 70.179.48.109 (talk) 07:46, 11 November 2008 (UTC)

Uncredited lines
I wrote this article: http://www.ridelust.com/obscure-burglary-tools-of-the-day-ninja-rocks/

which is where the line "Tempered glass used in automobile windows is softer on the Mohs scale than spark plug ceramic (specifically aluminum oxide ceramic). Aluminum oxide ceramic rates a 9 on the Mohs scale; diamonds are 10, glass is 6.5." came from.

The only references I used for that article were when I wikied the actual Mohs hardnesses of those particular materials. I wrote the rest from personal and professional knowledge. I would appreciate it if someone cited that line. Thank you. —Preceding unsigned comment added by 108.2.17.230 (talk) 13:44, 26 June 2010 (UTC)

Clarity maintenance tag
I recently rewrote the lead section to better explain the concept to someone unfamiliar with the subject, so if nobody has any problem with it then I am going to remove the maintenance tag at the top of the page. Orchastrattor (talk) 13:12, 20 May 2021 (UTC)