Top all-time · #2601
David Richeson: Division by Zero
Personal blog · divisbyzero.commathscience
David Richeson: Division by Zero is a personal blog at divisbyzero.com about math and science. Since 2010, 32 different Hacker News readers have linked it 55 times, most often “What are p-adic numbers? (2008)”. It is still writing: the last post was on 2026-02-01, and you can follow it by feed.
Professor of Mathematics and the John J. Curley '60 and Ann Conser Curley '63 Faculty Chair in the Liberal Arts at Dickinson College [Icons made by Freepik from www.flaticon.com.]
Most-linked posts?
- What are p-adic numbers? (2008)3 people · 3 mentions · first linked 2020-08-30
- Making the Mandelbrot Set with Excel3 people · 3 mentions · first linked 2024-11-13
- What is the difference between a theorem, a lemma, and a corollary?2 people · 2 mentions · first linked 2019-03-08
- Fold-and-Cut Hat and Spectre Tiles2 people · 2 mentions · first linked 2024-08-14
- Mathematical surprises2 people · 2 mentions · first linked 2010-08-20
- Tennenbaum's visual proof that the square root of 2 is irrational2 people · 2 mentions · first linked 2011-11-19
- Make a "Magic Eye" image using Excel2 people · 2 mentions · first linked 2024-12-01
- An application of graph theory to architecture2 people · 2 mentions · first linked 2011-10-04
What Hacker News says?
> I disagree that or is ambiguous There are examples of inclusive “or” in natural language. When the waiter asks: “Would you like cream or sugar?”, it’s not meant to imply that you should pick only one; it’s fine to answer “both” (example from: https://divisbyzero.com/2009/09/27/is-or-an-inclusive-or-or-... ).
Comment linking /2009/09/27/is-or-an-inclusive-or-or-an-exclusive-or/
on “If-then-else had to be invented”Submitted The Unknotting Number Is Not Additive as a story · 178 points
HN discussionI never knew Hokusai had interest in these. Does anyone know if he had seen any Islamic tiling art ? Or for that matter if Escher had seen any of his. Group theory / symmetry runs deep through these. One [0] of the circular ones made me think of braid(group)s. Not sure what the * operator would be in that case. Speaking of braid groups Richeson had a very interesting blog post on the braid like groups of maypole dan…
Comment linking /2009/05/04/the-maypole-braid-group/
on “Hokusai Moyo Gafu: an album of dyeing patterns”Submitted Turing's topological proof that every written alphabet is finite (2010) as a story · 138 points
HN discussionDo a little more research on Stanley Tennenbaum. This discovery happened around the 1950s. Tennenbaum didn't drop out of mathematics so much as he dropped out of institutional mathematics. More here, including a post from one of his children in the comments: http://divisbyzero.com/2009/10/06/tennenbaums-proof-of-the-i... Stanley's up in heaven now.
Comment linking /2009/10/06/tennenbaums-proof-of-the-irrationality-of-the-square-root-of-2/
on “The Power of Mathematics - John Conway [pdf]”Submitted Make a "Magic Eye" image using Excel as a story · 115 points
HN discussionBit of a logical play, the dilemmic fallacy to be precise, but, alternatively: If they're competent, leaving them a lot of money won't do them any harm. If they're not, they need his money. [edit] here's the classical example of this change in perspective: http://divisbyzero.com/2008/11/30/euathlus-and-protagoras/
Comment linking /2008/11/30/euathlus-and-protagoras/
on “Chinese philanthropist donates all his fortune”Submitted Proof Without Words: Gregory’s Theorem as a story · 97 points
HN discussionhttps://divisbyzero.com/2009/05/04/the-maypole-braid-group/ Of maypole dance and the algebra of braids
Comment linking /2009/05/04/the-maypole-braid-group/
on “The Nature of Dance”Submitted The math behind a neat calculator trick as a story · 74 points
HN discussion> Recently, somebody shared on Twitter a new proof As far as I can tell there is no link to this tweet in this post which is bad form to say the list. The post has multiple links promoting author's other posts, but not to the raison d'etre for this post. PS: Apparently, the author is Director of Research, Computer Laboratory, University of Cambridge which makes this lack of proper citation even more perplexing. PPS:…
Comment linking /2009/10/06/tennenbaums-proof-of-the-irrationality-of-the-square-root-of-2/
on “Formalising a new proof that the square root of two is irrational”Submitted Make Your Own Pythagorean Cup as a story · 48 points
HN discussionThis looks very similar to this http://divisbyzero.com/2010/03/14/an-application-of-graph-th...
Comment linking /2010/03/14/an-application-of-graph-theory-to-architecture/
on “How graph theory can reduce redundancy in trusses”Submitted Maypole Dance of Braid Like Groups (2009) as a story · 37 points
HN discussionSomething I found interesting, once you understand the proof of why there are "more" real numbers than integers, it becomes easy to see that the p-adic numbers[0], which can have infinite digits to the left of the decimal, but finite digits to the right, have the same cardinality as the real numbers (there are more of them than integers). This was unintuitive to me when I first thought about it, because I pictured a…
Comment linking /2008/11/24/what-are-p-adic-numbers/
on “How can some infinities be bigger than others?”Submitted Mathematical surprises as a story · 37 points
HN discussionDavid Richeson dives into the math behind it: https://divisbyzero.com/2018/02/13/finite-differences-of-pol...
Comment linking /2018/02/13/finite-differences-of-polynomials/
on “Finite differences of polynomials – Principle of the Difference Engines”Submitted The Most Imaginary Number Is Real as a story · 22 points
HN discussionSubmitted Making the Mandelbrot Set with Excel as a story · 8 points
HN discussionSubmitted I Heart Cardioids as a story · 6 points
HN discussionSubmitted Music is math: ten songs about mathematics as a story · 5 points
HN discussionSubmitted Musicians with PhD's as a story · 4 points
HN discussionSubmitted Mathematical surprises as a story · 4 points
HN discussionSubmitted What are p-adic numbers? (2008) as a story · 3 points
HN discussionSubmitted Volume of N-Dimensional Balls as a story · 3 points
HN discussionSubmitted Rubik’s Cube Tri-Hexaflexagon as a story · 3 points
HN discussionSubmitted The transcendence of e as a story · 3 points
HN discussionSubmitted An application of graph theory to architecture as a story · 3 points
HN discussionSubmitted Make a "Magic Eye" image using Excel as a story · 2 points
HN discussionSubmitted Making the Mandelbrot Set with Excel as a story · 2 points
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