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Discovery of a new irregular pentagon that can cover the plane

theguardian.com

111–120 of 131 posts

Re: Discovery of a new irregular pentagon that can cover the plane

#111

Wait a second. Aren't there actually two different pentagon shapes in use here? Look at the yellow and blue in the OP. They are actually mirror images of each other. Maybe a mathematician would say they are the same, but certainly not someone cutting tile for a bathroom floor. And if these were proteins trying to form a cell wall, that mirroring would be a serious hurdle.

All depends how you define "the same". Mathematicians use "congruency" which allows mirror images.

Re: Discovery of a new irregular pentagon that can cover the plane

#112
post #111

Wait a second. Aren't there actually two different pentagon shapes in use here? Look at the yellow and blue in the OP. They are actually mirror images of each other. Maybe a mathematician would say they are the same, but certainly not someone cutting tile for a bathroom floor. And if these were proteins trying to form a cell wall, that mirroring would be a serious hurdle.

All depends how you define "the same". Mathematicians use "congruency" which allows mirror images.

Ah. You learn something every day. I guess the guardian was therefore incorrect in their definition and should have said "congruent copies" ... but "copies" is also probably wrong. Congruent congruencies?

>"If you can cover a flat surface using only identical copies of the same shape leaving neither gaps nor overlaps, then that shape is said to tile the plane."

Re: Discovery of a new irregular pentagon that can cover the plane

#113
post #106

"Every triangle can tile the plane. Every four-sided shape can also tile the plane." Can someone point me to a proof of this?

The triangle is pretty easy: take two of the (same size) triangles, with vertices ABC and A'B'C'. Rotate and translate the second triangle to fit the matching side of the first triangle, e.g. AB to B'A'. You now have a quadrilateral with two pairs of equal sides (sides (AB')C and (A'B)C'). The angle on the corners comprised of the two triangles (e.g., C(AB')C') will add together to be 180 degrees minus the angle of the adjacent corners, due to the three interior angles of every triangle summing to 180 degrees. Duplicate that quadrangle and fit the second to a matching side. The angles put together will form 180 degrees, i.e., a straight line. Now you have indefinitely extensible strip. Place the strips next to each other and you've tiled the plane.

Re: Discovery of a new irregular pentagon that can cover the plane

#115

Earlier quoted context omitted.

The only person throwing accusations around is you. This is a huge blanket blaming statement: > 99% outsider science is extremely bad, and can't understand why it's bad even after repeated explanations A challenge dealing with noise in a system is an opportunity for a solution, not a rationalization to censor people. That < .01% may be onto something big.

Part of my point was that the 1% with good ideas aren't actually getting censored. If you can find any recent examples to the contrary, please let me know.

Part of my point was that the 'accusation' you claimed against 1arity was that communities exclude outsiders. That you made rationalizations about why they might be excluding outsiders (because they are bad) serves to illustrate that the community might very well be practicing exclusion, and with good reason. I'm challenging the status quo here, and looking for an opportunity to allow quacks to be quacks while we're still 100% open to finding people with decent ideas. That may be implausible, but I'm still challenging it. :)

For whatever reason, this reminds me of the recent TED talk that got pulled because the speaker was challenging dogma in research. Can't remember the title off the top of my head.

Re: Discovery of a new irregular pentagon that can cover the plane

#116

Earlier quoted context omitted.

Not to answer your question, but here's a simple, unsolved problem: Dissect the circle into congruent pieces such that the center point is in the interior of one of the pieces. It is widely believed to be impossible, but neither proof of impossibility nor construction of an example have been found.

Huh. Is it possible to dissect a circle into congruent pieces that are not, uh, pie shapes? Is that the question, or are there known other ways to dissect a circle into congruent pieces, it's just those pieces also have the center point as an edge point?

Non pie shapes are definitely possible - look at the taijitu (yin/yang) symbol for example - . But of course, again, the center is on the divide between both halves.

Re: Discovery of a new irregular pentagon that can cover the plane

#118

Earlier quoted context omitted.

Part of my point was that the 1% with good ideas aren't actually getting censored. If you can find any recent examples to the contrary, please let me know.

Part of my point was that the 'accusation' you claimed against 1arity was that communities exclude outsiders. That you made rationalizations about why they might be excluding outsiders (because they are bad) serves to illustrate that the community might very well be practicing exclusion, and with good reason. I'm challenging the status quo here, and looking for an opportunity to allow quacks to be quacks while we're…

If you're talking about Graham Hancock or Rupert Sheldrake, I'll stick with the dogma. I don't think you can talk to spirits or make telepathic contact with dogs.

Now I'm curious, how exactly did you come to believe that the scientific community is not welcoming to outsiders with good ideas?

Re: Discovery of a new irregular pentagon that can cover the plane

#119

Does anyone have a link to the actual paper?

I'm not certain there is an actual paper yet; I suspect from some of the phrasings that it was merely an announcement that their program succeeded, but a formal paper will take a while.

I did find this reddit post by Dr. Mann [1] where he says:

> We were just in the process of debugging and optimizing the code when our new example was found. Because we are in the early stages of the computational experiments, we were surprised to find this example so quickly. We are hopeful of finding more new examples as we proceed.

[1] https://www.reddit.com/r/math/comments/3fe347/15th_pentagon/...

Re: Discovery of a new irregular pentagon that can cover the plane

#120
post #111

Earlier quoted context omitted.

All depends how you define "the same". Mathematicians use "congruency" which allows mirror images.

Ah. You learn something every day. I guess the guardian was therefore incorrect in their definition and should have said "congruent copies" ... but "copies" is also probably wrong. Congruent congruencies? >"If you can cover a flat surface using only identical copies of the same shape leaving neither gaps nor overlaps, then that shape is said to tile the plane."

"Identical copies" is informal, as is "copies" for that matter. You can think of the information that is defining the shape as what is being copied, hence mirroring and other variations are allowed. A possibly related term to look into would be "isomorphism".
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