OU blog

Personal Blogs

Richard Walker


Visible to anyone in the world

Following my earlier post about CHECKBOOK, I wrote a Python program to find dictionary words with the property they have symmetry about a horizontal mirror line; if you invert them, they remains the same. I used the UK Advanced Cryptics Dictionary, by Ross Beresford (240732 words) as my word source.

Here is the full list of then 352 results. As you might expect some of the words are a wee bit obscure.


Permalink 1 comment (latest comment by Jan Pinfield, Saturday, 16 July 2022, 05:55)
Share post
Richard Walker

A Quick Geometric Problem

Visible to anyone in the world

Michael Penn put this up on his YouTube channel earlier today, and it is indeed an elegant little problem. Here it is

Michael Penn solves this using congruent triangles, the angle sum of a triangle (180 °) and angles on a straight line (180 °). α is always 60 °, whatever the length of AD and CE. It's not that obvious and I was quite surprised.

However thinking about it later, I saw we can solve the problem using symmetry and the solution is super-nice. Here's how - just add a third line.

Permalink Add your comment
Share post
Richard Walker

Snowflakes again

Visible to anyone in the world
Edited by Richard Walker, Saturday, 23 Jan 2010, 01:53

I've always thought symmetry was heart-breaking and snowflake patterns marvellous in their variety - and their temporary existence.  Bentley, the New England farmer who photographed so many snow crystals over 40 years (see earlier blog post snowflake(1)) lamented that each was unique and so beautiful, but gone forever in seconds or less.

Yesterday some of Bentley's original photos - plates I guess - were at auction and this was reported in many newspapers.  Go look



Permalink 1 comment (latest comment by Shankar Poncelet, Saturday, 13 Feb 2010, 07:36)
Share post
Richard Walker

A feeling for snow

Visible to anyone in the world
Edited by Richard Walker, Tuesday, 5 Jan 2010, 00:05

Miss Smilla's Feeling for Snow is a famous novel.  But Wilson Bentley also had a feeling for snow and was the pioneer of snowflake photography, see


A more recent photographer of snow crystals is Kenneth Libbrech, see



These images are all wonderful.

Looking at snowflakes many have asked how each of the six arms of the snowflake 'knows' how to keep itself in symmetry.



Permalink 4 comments (latest comment by Richard Walker, Saturday, 23 Jan 2010, 01:48)
Share post

This blog might contain posts that are only visible to logged-in users, or where only logged-in users can comment. If you have an account on the system, please log in for full access.

Total visits to this blog: 2134023