I was expecting to see the photos, but the jpg are linked there instead of visible. IIRC you were using a self-made CMS for your blog, with more support for math formulas. Does it not allow images?

That really is a MVP. Or perhaps MVD (Minimum Viable Demonstration).

Correct - we knew we could do that with balls, but can you do it with a pyramid? It initially seems like there would always be at least two stable surfaces for a pyramid, but this group managed to figure out how to do it with only one stable surface.

Last time I checked, spheres are shapes.

But the article references a "pyramid-like shape"

Yeah, but the challenge in this case was to achieve it without any rounded edges.

Does it work when 3rd printed? How sensitive is it to infill options or infill density variations?

That isn't true.

Look at the pictures. It has the same outer shape, that is all that is required for the geometry.

And for center of mass, you set the positions for the bars, any variations in their thickness, then size and place the flat facet, in order to achieve the same center of mass as for a filled uniform density object of the same geometry.

As the article says:

> carefully calibrated center of mass

Unless an object has internal interactions, for purposes of center of mass you can achieve the uniform-density-equivalent any way you want. It won't change the behavior.

Huh, now I'm curious, what did the D2 look like?

> the DM/GM could throw it at a player for effect without braining them!

If you're prepared to run over to wherever it ended up after that, sure.

I learned to juggle with ping pong balls. Their extreme lightness isn't an advantage. One of the most common problems you have when learning to juggle is that two balls will collide. When that happens with ping pong balls, they'll fly right across the room.

A sphere is bad, it rolls away. The shape from the article would be better, but it is too hard to manufacture. And weighting is cheating anyway. The best option for a D1 is probably the gömböc, which is mentioned in the article.

Nitpick: one of the properties of dice is that they stop on one side (i.e they converge towards stable rest on even ground) and the typical rule is that when they come at rest because of something other than even ground then the throw is invalid.

So while a sphere has only one side it basically never comes at a stable enough rest unless stopped by uneven ground (invalid throw), and if it stops because of friction it is unstable rest where the slightest nudge would make it roll again.

Therefore in a sense a sphere only works as a 1D because you know the outcome before throwing.

Edge cases are fun.

> Love it - any sphere will do.

That's basically what the link shows. A Möbius strip is interesting in that it is a two-dimensional surface with one side. But the product is three-dimensional, and has rounded edges. By that standard, any other die is also a d1. The surface of an ordinary d6 has two sides - but all six faces that you read from are on the same one of them.

Or any mobius strip

Everyone knows that a donut has two sides.

Inside, and outside.

You sunk my battleship!

Did you notice the column indicating number of items per box/carton?

Shockwatch is $170 for 50 items, for example, and the label $75 for 200.

Not dirt cheap, but I guess that’s because of the size of the market.

Fun fact: MythBusters used shock watches extensively when testing anything involving impact, because they were massively more reliable than any of their digital instrument.

Link wasn't a storefront or brand recommendation, just a handy overview for people unfamiliar with the category.

The SpotSee/ShockWatch brand does seem to be more expensive (almost $4 per device), but they have interesting variants like shock-triggered RFIDs.[0] Otherwise you can find competitor products at roughly half the price.[1]

[0] https://shop.spotsee.io/impact_indicators

[1] https://impactograph.com/product/shock-indicator-labels/

It may not just be monetary value. Shipping something that could be ruined by being thrown around (e.g. IIRC there were issues with covid-19 vaccine suspensions and sudden shocks ruining it) that just won't work may need this indicator even if the actual monetary value is otherwise low.

These are pretty normal when shipping scientific equipment.

Problem is when transporting tilt watchers, you can’t tilt the package either.

I think you’re overthinking it. The tamper mechanism being proposed is just a thin straight stick standing on its end. Disturb it, it falls over.

Gábor Domokos (mentioned in the article) talked about this on one QI episode:

https://www.youtube.com/watch?v=ggUHo1BgTak

Mars landers have also had a chequered history. I remember one NASA jobbie that had a US to metric units conversion issue and poor old Beagle 2 that got there, landed safely and then failed to deploy properly.

That article doesn't prove what you say that it does. It just proves because a perpetuum mobile is impossible, it is trivial that a polyhedron must always eventually come to rest on one face. It doesn't assert that the face-down face is always the same face (unistable/monostable). It goes on to query whether or not a uniformly dense object can be constructed so as to be unistable, although if I understand correctly Guy himself had already constructed a 19-faced one in 1968 and knew the answer to be true.

To support your point, and pre-empt some obvious objections:

- I've ridden a bike with a bamboo frame - it worked fine, but I don't think it was very durable.

- I've seen a video of a belt- (rather than chain-) driven bike - the builder did not recommend.

You maybe get there a couple of decades sooner with a bamboo penny-farthing, but whatever you build relies on smooth roads and light-weight wheels. You don't get all of the tech and infrastructure lining up until late-nineteenth c. Europe.

It's funny, I was wondering about the exact example of a bicycle a few days ago and ended up having a conversation with Claude about it (which, incidentally, made the same point you did). It struck me as remarkable (and still does) that this method of locomotion was always physically possible and yet was not discovered/invented until so recently. On its face, it seems like the most important invention that makes the bicycle possible is the wheel, which has been around for 6,000 years!

Oops disregard this, by "has to be identical" I thought you were objecting to the non uniformity of the surface, not the incongruity of the sides' shapes, so that's where my comment was coming from.

The incongruity of the sides certainly makes it not a Platonic Solid, though the article doesn't actually assert that it is. It just uses some terrible phrasing that's bound to mislead. Their words with my clarification for how it could be parsed in a factually accurate way: "A tetrahedron is the simplest Platonic solid (when it's a regular tetrahedron). Mathematicians have now made one (a tetrahedron, not a Platonic solid)...".

It's a dumb phrasing, it's like saying "Tesla makes the world's fastest accelerating sports car. I bought one" and then revealing that the "one" refers to a Tesla Model 3, not the fastest accelerating sports car.