Dice arrangement in a centrifuge

This 2017 Physics Today article reports analysis of dice packing and arrangement in a low speed centrifuge. Suggested to me by a forum member.

Dice packing and arrangement in a low-speed centrifuge

Very little relevance to dice control in gambling. As a physicist, I found this interesting because it quotes level of rotational force(~0.5 g) at which the behavior of the "dice pack" suddenly changes.

Sure, you need enough radial force to overcome the friction between the dice due to the axial force of gravity. They could test that by throwing some graphite powder in there as a lubricant, see if that changes that threshold acceleration.

The ordering should also happen more quickly at the top of the cylinder and work its way down, as the corners of the higher dice are no longer digging into the pips of the dice on the layer below them. Hey maybe it does have a connection to dice control, and I'd bet that there is some non-randomness in the orientation of the dice as a craps player would see them due to the resistance caused by the pips.

Sufficiently vigorous twisting of a cylinder containing 25,000 randomly-oriented dice (left) leads to a nearly perfectly ordered arrangement (right). What I felt was notable was how most of the dice are seemingly arranged with one pip in the outward direction.

Quote: gordonm888

Sufficiently vigorous twisting of a cylinder containing 25,000 randomly-oriented dice (left) leads to a nearly perfectly ordered arrangement (right). What I felt was notable was how most of the dice are seemingly arranged with one pip in the outward direction.
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This is an easy math problem. The orientation of a dice depends only on its center of mass. If they are really oriented one way preferably, they were not manufactured symmetrical enough.

Quote: aceside

Quote: gordonm888

Sufficiently vigorous twisting of a cylinder containing 25,000 randomly-oriented dice (left) leads to a nearly perfectly ordered arrangement (right). What I felt was notable was how most of the dice are seemingly arranged with one pip in the outward direction.
link to original post

This is an easy math problem. The orientation of a dice depends only on its center of mass. If they are really oriented one way preferably, they were not manufactured symmetrical enough.
link to original post

Would mean the side with one pip is heavier since out is “down”.

Quote: unJon

Quote: aceside

Quote: gordonm888

Sufficiently vigorous twisting of a cylinder containing 25,000 randomly-oriented dice (left) leads to a nearly perfectly ordered arrangement (right). What I felt was notable was how most of the dice are seemingly arranged with one pip in the outward direction.
link to original post

This is an easy math problem. The orientation of a dice depends only on its center of mass. If they are really oriented one way preferably, they were not manufactured symmetrical enough.
link to original post

Would mean the side with one pip is heavier since out is “down”.
link to original post

If you think of a pip, which is a depression, as negative weight, then this makes conceptual sense. I am surprised that the tiny weight difference is so determinative.

I haven’t read the article, but I can imagine how the experiment was performed. First, they manufactured one million or so cubes, and then, they marked them by paint one by one. When they marked each cube, they always picked the upside of a cube to mark it as the one pip side, according to their programmed lathe. However, this marking process was already biased to begin with because the lighter side of a cube always tended to face upward.

According to the article, these dice are about 1/2 centimeter on a side, which is tiny! There are about 50,000 of these miniature dice used in the tests so I suspect they were indeed "manufactured' and painted for this experiment, (perhaps by a contractor.) They are said to be "plastic." No telling what specifications they were manufactured to.

There is an 8 second video in the article (at the url link given in the first post) in which you can see the dice go from a random jumble to a closely-packed ordered array in the cylindrical centrifuge. This WOV site is only set-up for embedding You Tube videos, so I cannot easily post it here. One really needs to click on the link, open up the article and click on the video.

Now they need to try it with backgammon dice, rounded edges and corners. Totally different results I am sure.

I think the appearance of a bias toward the 1 side facing outward is illusory. It's the only side you can really distinguish in the picture.

Quote: gordonm888

According to the article, these dice are about 1/2 centimeter on a side, which is tiny! There are about 50,000 of these miniature dice used in the tests so I suspect they were indeed "manufactured' and painted for this experiment, (perhaps by a contractor.) They are said to be "plastic." No telling what specifications they were manufactured to.

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5mm dice in this pip style are readily available from trade suppliers.

https://www.aliexpress.us/item/3256806572876971.html

Quote: AutomaticMonkey

Now they need to try it with backgammon dice, rounded edges and corners. Totally different results I am sure.

I think the appearance of a bias toward the 1 side facing outward is illusory. It's the only side you can really distinguish in the picture.
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i agree. I zoomed in on the photo and there does not appear to be a preponderance of single pips facing outward in the cylinder. Just an illusion created by how distinctive the single pip is.

Quote: AutomaticMonkey

Now they need to try it with backgammon dice, rounded edges and corners. Totally different results I am sure.

I think the appearance of a bias toward the 1 side facing outward is illusory. It's the only side you can really distinguish in the picture.
link to original post

i agree. I zoomed in on the photo and there does not appear to be a preponderance of single pips facing outward in the cylinder. Just an illusion created by how distinctive the single pip is.