# A flipped coin landing on its edge. **URL:** \ **Category:** Factual Questions\ **Created:** [April 4, 2011, 7:32am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126 "2011-04-04T07:32:46Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [April 4, 2011, 8:59pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/21 "2011-04-04T20:59:29Z")
Is that a tuna can with [oil or water](http://boards.straightdope.com/sdmb/showthread.php?t=602459)? ---
**Author:** ![Manlob](https://avatars.discourse-cdn.com/v4/letter/m/96bed5/32.png) [@Manlob](https://boards.straightdope.com/u/Manlob)\ **Post date:** [April 4, 2011, 11:23pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/22 "2011-04-04T23:23:56Z")
If the coin is given a random orientation (with no bias toward any particular orientation), moved into contact with the surface, and released with no momentum or angular momentum, the probability is based on the solid angle from center of mass of the rim. This results in probability of ending up on its edge of t/sqrt(D_D+t_t), where t= thickness (2 mm) and D is diameter (26.49 mm), giving probability of 7.5%. If you want to give the coin some sort of momentum, angular momentum, or bias toward a particular orientation when it first makes contact with the surface, then further clarification is required in the question. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 5, 2011, 12:00am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/23 "2011-04-05T00:00:03Z")
> [@Manlob](#): > > If the coin is given a random orientation (with no bias toward any particular orientation), moved into contact with the surface, and released with no momentum or angular momentum, the probability is based on the solid angle from center of mass of the rim. This results in probability of ending up on its edge of t/sqrt(D_D+t_t), where t= thickness (2 mm) and D is diameter (26.49 mm), giving probability of 7.5%. > > If you want to give the coin some sort of momentum, angular momentum, or bias toward a particular orientation when it first makes contact with the surface, then further clarification is required in the question. You work for [Microsoft](http://funnyjoke.wordpress.com/2006/12/16/technically-correct-but-a-completely-useless-answer/), don’t you? ---
**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:** [April 5, 2011, 1:34am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/24 "2011-04-05T01:34:32Z")
> [@](#): > > If the coin is given a random orientation (with no bias toward any particular orientation), moved into contact with the surface, and released with no momentum or angular momentum, the probability is based on the solid angle from center of mass of the rim. This results in probability of ending up on its edge of t/sqrt(D_D+t_t), where t= thickness (2 mm) and D is diameter (26.49 mm), giving probability of 7.5%. This works for a right circular cylinder, but not in general: Most general shapes will have surfaces on which they can’t come to rest at all, despite nonzero solid angles to those surfaces. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [April 5, 2011, 2:35am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/25 "2011-04-05T02:35:05Z")
Sorry for the hijack… But has anyone ever flipped a cig. butt to the ground, and had it come to rest on its _end_? :eek: I _ **have** _. And would have bet you (at that moment) _ **THAT** _, will never happen again! And of course, it damn sure **DID** , happen again! :smack: Granted, it was about twenty odd years later. 😛 I wonder what the odds are, that I’ll do it a _third_ time?😃 (Both times, I was standing on clean, smooth concrete. Just sayin’…) ---
**Author:** ![Indian](https://avatars.discourse-cdn.com/v4/letter/i/c0e974/32.png) [@Indian](https://boards.straightdope.com/u/Indian)\ **Post date:** [April 5, 2011, 7:44am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/26 "2011-04-05T07:44:06Z")
This was posed to me by a student (without attaching any conditions/ coin specification). This not being so simple (student argued it should be 1/3),I picked the U.S coin size and posted in dope (where else? ;)). He meant it this way. " What is the probability of a coin landing ion its edge in a normal flip (coin rotates with its diameter as axis),assuming coin bounces in a random way and finally comes to rest on its edge." ---
**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:** [April 5, 2011, 5:54pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/27 "2011-04-05T17:54:23Z")
If your student is saying the probability should be 1/3, there’s an easy way to prove him wrong: Take a coin out of your pocket and offer to pay him $3 (or heck, make it $4-- You want him to be able to make a profit) if it lands on edge, but if it lands on a face, he has to pay you $1. Offer to repeat the bet as many times as he’d like. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [April 5, 2011, 8:27pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/28 "2011-04-05T20:27:09Z")
> [@Chefguy](#): > > I seem to recall a Twilight Zone episode that started this way. See link in post #6 ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [April 7, 2011, 8:16am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/29 "2011-04-07T08:16:14Z")
My brother once had this happen. What’s really mind-boggling is that before he flipped it he, as a goof, _ **called the edge!!** _ The girl he was betting with was, ahem, not real bright so while my brother stood there in jaw-dropping astonishment she couldn’t have cared less. ---
**Author:** ![MensaMaster](https://avatars.discourse-cdn.com/v4/letter/m/ee59a6/32.png) [@MensaMaster](https://boards.straightdope.com/u/MensaMaster)\ **Post date:** [March 8, 2012, 11:44pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/30 "2012-03-08T23:44:59Z")
Sounds extremely strange but since I almost shot myself in the head with a pistol by accident 10 years ago I have landed Quarters, Nickels and even Asprin tablets on their “edge” on just a casual flip. I have had witnesses to this and gave us all goose bumps. Always wondered if their was something that assisted these uncanny events? ---
**Author:** ![Measure\_for\_Measure](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/measure_for_measure/32/557_2.png) [@Measure\_for\_Measure](https://boards.straightdope.com/u/Measure_for_Measure)\ **Post date:** [March 9, 2012, 7:16am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/31 "2012-03-09T07:16:39Z")
> [@FoieGrasIsEvil](#): > > Would the slightly lighter gravity at the equator make a difference? Can’t you do weird things there like stand an egg on its end? > [@Colophon](#): > > No. That’s a myth used to suck in tourists in Africa and South America. 😛 > > Gravity is only about half of one percent weaker at the equator than at the poles. Well it’s not a complete myth. You actually can stand an egg on its end on the equator. Then again, you can also do it in Chicago. [The Master speaks](http://www.straightdope.com/columns/read/416/can-you-stand-eggs-on-end-at-the-vernal-equinox-and-at-no-other-time): > [@Cecil Adams](#): > > Moral: you can stand an egg on end any old time. All it takes is very steady hands. Also, it seems to work better if you shake up the egg first. This breaks the yolk loose from the bands (chalazae) that keep it suspended in the center of the egg, lowering the egg’s center of gravity. But that’s cheating. ---
**Author:** ![Indian](https://avatars.discourse-cdn.com/v4/letter/i/c0e974/32.png) [@Indian](https://boards.straightdope.com/u/Indian)\ **Post date:** [March 11, 2012, 1:33pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/32 "2012-03-11T13:33:41Z")
per this [study.](http://pre.aps.org/abstract/PRE/v48/i4/p2547_1) (Subsequent to starting this thread, I searched online and located above study.) Also, And coin flipping can be [manipulated.](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789164/) _Certain people are able to successfully manipulate the toss of a coin. This throws into doubt the validity of using a coin toss to determine a chance result._ ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [March 12, 2012, 4:23am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/33 "2012-03-12T04:23:31Z")
> [@CookingWithGas](#): > > …Try running a million trials and let us know what you find out. If you do get it to land on the edge, also let us know if you can [read minds](http://www.tv.com/the-twilight-zone/a-penny-for-your-thoughts/episode/12636/summary.html).🙂 Or the Governor just might appoint you to the U.S. Senate. ---
**Author:** ![rsparkeriii](https://avatars.discourse-cdn.com/v4/letter/r/c57346/32.png) [@rsparkeriii](https://boards.straightdope.com/u/rsparkeriii)\ **Post date:** [April 24, 2012, 8:58pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/34 "2012-04-24T20:58:23Z")
> [@JBDivmstr](#): > > Sorry for the hijack… But has anyone ever flipped a cig. butt to the ground, and had it come to rest on its _end_? :eek: I _ **have** _. And would have bet you (at that moment) _ **THAT** _, will never happen again! And of course, it damn sure **DID** , happen again! :smack: > Granted, it was about twenty odd years later. 😛 > I wonder what the odds are, that I’ll do it a _third_ time?😃 > (Both times, I was standing on clean, smooth concrete. Just sayin’…) JBDivmstr, I flipped cigarettes twice also to land on butts. I had a witness the first time. It was over a span of about ten years. I thought I was the only one.:smack: ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [April 24, 2012, 11:43pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/35 "2012-04-24T23:43:34Z")
But if you can make it happen, you can read minds. 😉 ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [April 25, 2012, 12:10am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/36 "2012-04-25T00:10:32Z")
All this time and no mention of _Mr. Smith Goes to Washington_? Also, a tossed bat after a hit at a MLB baseball game would up upright a year or two ago. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [April 25, 2012, 1:00am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/37 "2012-04-25T01:00:38Z")
Incidentally, I made a [computer simulation](http://www.youtube.com/watch?v=WFG1OP5OmAw) once that figured out you need a coin with a height 1.33 times it’s radius to have an exact equal probability of landing on all 3 faces. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [April 25, 2012, 1:15am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/38 "2012-04-25T01:15:49Z")
> [@garygnu](#): > > All this time and no mention of _Mr. Smith Goes to Washington_?.. See post #33. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [November 24, 2012, 9:43pm UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/39 "2012-11-24T21:43:52Z")
From my Forgotten English word-a-day calendar for Nov. 23: “Nadgers: An expression used when a coin, in tossing, falls upon its edge - neither head nor tail up. - R. Pearse Chope’s _Dialect of Hartland, Devonshire_, 1891.” ---
**Author:** ![Indian](https://avatars.discourse-cdn.com/v4/letter/i/c0e974/32.png) [@Indian](https://boards.straightdope.com/u/Indian)\ **Post date:** [November 25, 2012, 2:23am UTC](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126/40 "2012-11-25T02:23:34Z")
Urban dictionary says it is all balls. [Previous page](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126.md?page=1) [Next page](https://boards.straightdope.com/t/a-flipped-coin-landing-on-its-edge/577126.md?page=3)