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Prince Rupert's cube

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11–20 of 43 posts

Re: Prince Rupert's cube

#11
Another nice puzzle:

A cube looks like a square from three orthogonal directions. A cylinder can look like a square from infinitely many directions, but they are all coplanar. Can you find a convex shape that looks like a square from more than three directions, without all of them being coplanar? In particular, can you find a convex shape that looks like a square from two distinct sets of three orthogonal directions? Can you find all such shapes?

Re: Prince Rupert's cube

#12
post #10

A video is worth a thousand words of theory: https://www.youtube.com/watch?v=-2jjgHsxEu4

After watching the video, I feel like this follows intuitively from the fact that sqrt(2) > 1.

The biggest possible difference between Prince Rupert's cubes is 3%, which is much smaller than the difference between sqrt(2) and 1.

Re: Prince Rupert's cube

#13

Another nice puzzle: A cube looks like a square from three orthogonal directions. A cylinder can look like a square from infinitely many directions, but they are all coplanar. Can you find a convex shape that looks like a square from more than three directions, without all of them being coplanar? In particular, can you find a convex shape that looks like a square from two distinct sets of three orthogonal directions?…

Do mathematicians consider this an open problem or does there exist a well known solution? And what about a name for this problem, does it have one already?

Re: Prince Rupert's cube

#14

Another nice puzzle: A cube looks like a square from three orthogonal directions. A cylinder can look like a square from infinitely many directions, but they are all coplanar. Can you find a convex shape that looks like a square from more than three directions, without all of them being coplanar? In particular, can you find a convex shape that looks like a square from two distinct sets of three orthogonal directions?…

Do mathematicians consider this an open problem or does there exist a well known solution? And what about a name for this problem, does it have one already?

Nah, it's nothing as grand as that. I saw it on facebook a few months ago and solved it in about ten minutes, just wanted to share the fun.

Re: Prince Rupert's cube

#15

Earlier quoted context omitted.

Do mathematicians consider this an open problem or does there exist a well known solution? And what about a name for this problem, does it have one already?

Nah, it's nothing as grand as that. I saw it on facebook a few months ago and solved it in about ten minutes, just wanted to share the fun.

...do you know the story of George Dantzig?

https://en.wikipedia.org/wiki/George_Dantzig#Mathematical_st...

I don't mean to say that it seems applicable here - but I also don't mean to say that it doesn't seem applicable here.

Re: Prince Rupert's cube

#16

Another nice puzzle: A cube looks like a square from three orthogonal directions. A cylinder can look like a square from infinitely many directions, but they are all coplanar. Can you find a convex shape that looks like a square from more than three directions, without all of them being coplanar? In particular, can you find a convex shape that looks like a square from two distinct sets of three orthogonal directions?…

Am I allowed to invoke hypercubes because that would cut this knot nicely.

Re: Prince Rupert's cube

#17

Another nice puzzle: A cube looks like a square from three orthogonal directions. A cylinder can look like a square from infinitely many directions, but they are all coplanar. Can you find a convex shape that looks like a square from more than three directions, without all of them being coplanar? In particular, can you find a convex shape that looks like a square from two distinct sets of three orthogonal directions?…

Orthographic or perspective projection?

Re: Prince Rupert's cube

#18
I knew of Prince Rupert’s drop before[1]. Reading about Prince Rupert’s cube sent me down the rabbit-hole of reading up on Prince Rupert himself.

Why do we no longer have Renaissance men/women today, contributing to the sciences, philosophy and the arts? What did we lose?

[1] https://en.m.wikipedia.org/wiki/Prince_Rupert%27s_Drop

Re: Prince Rupert's cube

#19

Another nice puzzle: A cube looks like a square from three orthogonal directions. A cylinder can look like a square from infinitely many directions, but they are all coplanar. Can you find a convex shape that looks like a square from more than three directions, without all of them being coplanar? In particular, can you find a convex shape that looks like a square from two distinct sets of three orthogonal directions?…

Orthographic or perspective projection?

I only know the solution for orthographic. But it seems like perspective would be too easy, just make any shape with many square sides, and put the cameras close to the sides.

Re: Prince Rupert's cube

#20
post #18

I knew of Prince Rupert’s drop before[1]. Reading about Prince Rupert’s cube sent me down the rabbit-hole of reading up on Prince Rupert himself. Why do we no longer have Renaissance men/women today, contributing to the sciences, philosophy and the arts? What did we lose? [1] https://en.m.wikipedia.org/wiki/Prince_Rupert%27s_Drop

> Why do we no longer have Renaissance men/women today, contributing to the sciences, philosophy and the arts? What did we lose?

A lot of the low-hanging fruit has already been claimed, and it's very difficult now for amateurs to make discoveries in mathematics and physics. There are people today doing amazing research, it just takes a career and a team (and in many cases expensive equipment) to do so.

If by "Renaissance men/women" you mean "well-versed/engaged in many topics", well, you just need to open your eyes. There are many folks like this now, likely millions. It was a bit more of a rarity a few hundred years ago, so it was much easier for these individuals to be documented/preserved.

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