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Trick dice have been used in gambling and magic shows. These are dice that, when rolled, will land with a preferred number facing upwards. This makes the result of rolling the dice non-random.

I was able to find a few ways to make trick dice, and I'm sure there are many more methods.

  1. Melt the dice in an oven.
  2. Drill and fill a hole with heavier material.

While these methods do work, they are not flawless. It's possible for the dice to still produce an unwanted result.

I was wondering with new materials like liquid metal and such things. Is it possible to create a truly flawless die, which when thrown on a flat surface will always produce the same result?

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By flawless do you mean it always falls with side 3 up (say), never any other side? Then I think it would have to be active so, for example, if you placed it on the table with side 4 up, it would detect it and spin a momentum wheel or something inside it to flip itself to the 3. –  Mike Dunlavey Oct 16 '12 at 1:57
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Additionally, one must also say that even half-perfect trick dice look noticeably weird when tumbling and are pretty easy to detect as such. For an effective die you'd need some remote control of an active mechanism, kind of ocean's-thirteen style. –  Emilio Pisanty Oct 16 '12 at 11:39
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@Mathew: Well, as long as the die is "smart" (having a computer, battery, accelerometer, and momentum wheels inside), then it shouldn't be too hard to program it so if it is simply placed down it will look innocent and not flip :-) –  Mike Dunlavey Oct 16 '12 at 19:05
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@Mathew: There's an even better way to do it. just play god. Film it being thrown down many times, delete all but the cases where it got 3, and post it on Utube. It'll go "viral" :-) –  Mike Dunlavey Oct 16 '12 at 19:08
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@MikeDunlavey - it'll only go viral if it's thrown by a kitten. –  Mathew Foscarini Oct 16 '12 at 19:09
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4 Answers

up vote 2 down vote accepted

I think it is possible but would require advanced electronic sensors and some kind of moterized spinning system inside it. If there are no external forces, angular momentum is conserved. So if the internal mechanisms spin one way the dice will have a torque the opposing way.

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+1 Interesting answer, the die however would however fall rather suspiciously in comparison to other dies. –  Prathyush Oct 15 '12 at 21:28
    
true, but I don't think this has been done by someone in a similar form factor (i.e. nano control of such a small object). –  Mathew Foscarini Oct 15 '12 at 22:17
    
I don't think anything very similar has been done. But I think it is doable with enough resources. I agree it may be much harder to do it in a way that doesn't look suspect. –  physicsphile Oct 15 '12 at 23:41
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There are at least urban myths of dies with internal chambers filled with mercury. When held in a particular way the mercury flows into a chamber opposite the desired number, making that side of the die heavier, but when held in another way the mercury flows back into the center so the die behaves essentially as normal.

This is necessary for games where both players use the same die - otherwise there wouldn't be much point having a rigged one which came up 6 for both of you!

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that's cool. I like that idea. –  Mathew Foscarini Oct 16 '12 at 0:23
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Passive flawless trick die is possible only if it has not cubic shape. That is in any position except the desired its center of mass's projection to the horizontal plane should be outside of the area which is in contact with base plane.

This is a principle of Ploy-toy doll. You can start with a spheric ploy-toy and then add some tiny "ribs".

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if it's not cubic shaped, then it's no longer a die. It has to look like a real die, otherwise people would know it was fake. –  Mathew Foscarini Oct 16 '12 at 3:51
    
@Mathew Foscarini in that case it is impossible. –  Anixx Oct 16 '12 at 4:28
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Possible, as the die is not in fact an exact cube, there is a bevel on the edges. So the 'always down' face must be coated with enough Neutronium to shift the center of gravity over the edge of the bevel.

What, no Neutronium?? Maybe use Tungsten, and the rest of the die of aerogel.

There will be a very small chance it can land heavy side up, though. It would be stable in that position, too.

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I don't think aerogel would be solid enough to stay together when thrown. The die would fall apart as it rolled. –  Mathew Foscarini Oct 16 '12 at 3:53
    
Just checked this video. It's to fragile. Otherwise, it was a good idea! youtube.com/watch?v=kHnen2nSmDY –  Mathew Foscarini Oct 16 '12 at 3:55
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