Richard Parkins web page

This is the web page of Richard Parkins, last updated 3 June 2022. If it has not been updated for a long time, I may be no longer active.

Some of the images are thumbnails to fit in a browser window. For a higher resolution view of any image, just click on it.

Cookie and privacy declaration

This web site does not use or set cookies, nor does it collect information from your browser or your computer or keep any record of your visit. It is written in hand-coded HTML and does not load scripts images, or any other content, from anywhere else. It does contain links to other web pages, and these are all explicitly labelled as such. I would not knowingly include a link to any malicious web page, but I cannot be responsible for the action of other web page authors. Your browser should enable you to examine the destination of a link without following it. If you are not happy with the policies of the destination web page, you should not follow the link.

This web page is still under construction, so there may be more of it next time you look: I try to remember to change the last updated date at the top of this page whenever I change anything.

Opening screw top jars

I've seen lots of reviews of grocery products recently complaining about the difficulty of opening screw top jars. This little trick may help. Slip the handle end of a spoon or a wide screwdriver under the edge of the lid, as in this picture.

Now lever the the lid gently away from the glass. Don't push too hard or you will crack the glass. You may have to try several places around the lid. Eventually you will hear a hiss as the air gets in to fill the partial vacuum inside which is holding the lid down. Then it will be much easier to unscrew the lid. I've successfully used this trick for many years.

If you suffer from tinnitus ("ringing in the ears"), this page may help you.

I have lived and worked in Scotland, Belgium, Switzerland, and the USA as well as England. Currently I live in Cambridge, England. If you have good reason to need my full address ask at the email below.

I design and make things. For almost all of my working life, I designed and made computer software, but I have retired from paid work. For a brief (and currently incomplete) history of my working life see here. I still work on my own, mostly open-source, projects. Currently I'm working on an open-source editor for sqlite databases. It is an improved version of sqliteman, and you can download the source code or a built version for Linux at this github page.

I'm also working on an Android application which generalises the idea (supported by several currently available apps) of muting your phone's ringer while your calendar says you have some sort of active event, such as a meeting. My version allows you to set up classes of calendar events and cause your phone to take different types of action according to the class of the currently active event. You can find it at this github page.

Other possibly useful repositories on github are:-

An app to list and show the values of all the sensors in an Android device
Another Android app which provides a home screen widget which can be configured to display any or all of A Linux shell script which starts Android Studio and displays a message while it is starting. This can be easily modified to keep track of any program that takes a long time to get started.

A Linux driver for a 3D printer, with some improvements over the original version which appears to be no longer maintained.

I have always been interested in Mathematics (for an early maths adventure see here) and I studied Mathematics at Trinity College, Cambridge. However I defected to computers and made my career in that area.

I am a collector of puzzles and I also design and make puzzles of various kinds. This movie shows one of my puzzles disassembling and then reassembling itself. If you want to buy one, it is available on the web at this web site.

Here are three more of my puzzles. They are all available to buy on another web site here.

I also both collect and make puzzle rings: here is a composite picture of a puzzle ring that I designed and made, in the folded and unfolded states. The configuration is called Borromean Rings after the Italian family of Borromeo, who used it as a family emblem (on another web site). The three rings are linked, but if you delete one ring, the others are not linked. The puzzle was originally designed (many years ago) as a result of a discussion which started from the (bought) puzzle rings which I owned at the time. Someone wondered if it was possible to make a puzzle ring with this linkage, so I went home, designed it, and made one. The gold one illustrated is one that I made more recently, after the restrictions on people owning gold bullion were removed.

If you live in, or visit, Cambridge, you can see some sculptures with the same linkage outside the Isaac Newton Institute for Mathematical Sciences in Clarkson Road.

A generalisation of this linkage to more than three rings is called a Brunnian Link. This is a set of loops which are linked, but if any single loop is removed, the others are not linked. For any number n 3 or greater, there exist (infinitely many distinct) Brunnian links with n loops. One possible link looks like a chain: below is a picture of one on a young lady's wrist - thanks to Leyla for modelling it.

If you want such a bracelet, or a necklace with more loops, you can buy the loops on the Internet at this web site. This movie shows how to assemble the links into a chain.

This is another piece of puzzle jewellery, in this case a bangle.

The two pieces slide together as in this movie. Once you put it on your wrist, the two pieces cannot come apart because your wrist is in the way. You can also buy this one on the Internet at this web site.

This movie shows another puzzle bangle sliding together. This one uses a bidirectional sliding system to make it fit snugly on the wearer's wrist. You can buy one here.

This more recent ring design also has three loops, but a different topology. In this case each loop is linked to the others so that the three of them form a closed chain. There is more than one way of doing this: the commonly seen ring with three gold loops of different colours of gold is also a closed chain, but not the same linkage.

I also have puzzle rings with closed chains of four and five links. Somewhere I think I have a design for one with six links, but I have not got round to making that one. Incidentally the well-known "Turkish" puzzle ring is also a closed chain of four links, but again my design is a different linkage. I put "Turkish" in quotes because my researches suggest that the design actually originated in Latin America. I have several rings of the "Turkish" design, mostly with some or all of the individual wires replaced by two or three parallel ones.

The almost certainly false story is that the design was used as a Turkish wedding ring. If the wife wanted to have an adulterous affair, she would take off her wedding ring and not be able to put it together again (a very sexist assumption), and so the husband would find out. There is of course another very sexist assumption here that a married woman might want to have an adulterous affair, but she needs to take off her wedding ring because otherwise a Turkish man would see the wedding ring and not want to have an affair with a married woman.

Islamic law (and indeed Jewish law in biblical times) does not require married men to be faithful to their wives. The normal English translation of the seventh commandment (לֹא תִנְאָף in the original Hebrew) as "Thou shalt not commit adultery" is really incorrect since adultery in English includes an affair between a married man and a woman who is not his wife, and the Hebrew word does not include that meaning: only an affair between a married woman and a man who is not her husband is forbidden. Yes, that's sexist too, but don't blame me, I didn't write it: I'm just clarifying the originally intended meaning.

I don't sell puzzle rings: it's too much work to make them compared with what I could reasonably charge. If you are a jeweller and you are interested in making my puzzle ring designs under licence, please get in touch.

A piece of mathematical jewellery (but not a puzzle) which I do sell is this earring or pendant which is based on a three-dimensional space-filling curve. You can buy it at this web site. For some of my earlier writings on two-dimensional space-filling curves see the references below.

This is a coffee table with a glass top and a hollow space underneath which I designed and made to display some of my collection of puzzles. For a discussion about how I came to make it, see here.

As a puzzlist I am of course interested in Rubik Cubes. I own Rubik cubes of sizes 2, 3, 4, 5, 6, 7, and 8. I have solved sizes 3, 4, and 5, although I seem to have lost the order 5 solution, and it was too complicated to remember. The order 2 one is too easy to bother with a formal solution. One problem with real Rubik cubes is that once you get it out of the standard position, it is hard to keep track of what you are doing. For this reason I made a virtual one. If you have FreeCAD on your computer, or are willing to download it, you can play with my virtual one. It is a FreeCAD (see the website) macro and you can find it at this web site. There is a similar puzzle called the Megaminx (wikipedia entry) based on the regular dodecahedron: it has twelve faces each a different colour rather than six. I also made a FreeCAD macro with a virtual version of that, which you can find at this web site.

Like some other puzzlists, I also think about physical problems in the real world. Many years ago I was making a cup of coffee, and I had poured the coffee into the cup and was about to add the milk when the doorbell rang. The question that I thought of was whether I should add the milk before answering the doorbell or afterwards. The utility function (what I wanted to maximise) was the temperature of the coffee and milk mixture by the time I got to drink it. Microwave ovens had not been invented by then, so if it took too long to deal with whoever was at the door and the coffee got too cold, the only choice was to throw it away and make a fresh one.

It took me about 30 years to get around to writing down the equations and solving this problem. Later I realised that there is a simple solution which does not require any equations at all. I encourage you to try and solve it for yourself before looking at the answer here.

I cam also interested in word puzzles. If you want to crack your brains a bit, try to find five eight-letter English words which are anagrams of each other (made of the same eight letters in different orders). They are all reasonably common words. Another word puzzle of mine is to find pairs of words which are spelled the same but pronounced differently and etymologically unrelated. The etymologically unrelated condition is needed to exclude words such as contract where the noun is pronounced differently from the verb. I know of three such pairs, although only one pair are really common words, and one of the others doesn't work in American English where the two are pronounced the same. I'm not giving solutions here.

Another of my interests is the ambiguity of the English language, a major issue for AI researchers trying to write software to understand English. Some examples that have amused me are here.

I am an active member of the Cambridge Union Society, probably the oldest member regularly active. This is a video on YouTube of the Union's bicentenary debate in which I spoke about 50 minutes into the debate. There are plenty of other Union debate videos on YouTube. There is also a Tab interview about me and the Union on the Tab's web page.

I also used to be a regular Arena promenader. Unfortunately the travelling and queueing got too much for me and nowadays I go only occasionally and usually sit in the stalls. At this web site is a picture of me dressed up for the Last Night of the Proms in 2005. There is another photograph of me queueing for the Last Night in 1998 on the front cover of Classical Music dated 4th September 1999: I can't reproduce it here for copyright reasons. I still go to concerts in Cambridge as well.

This bread machine story amused some of my friends when I told it to them: it may amuse you too.

If you have ever wondered at the remarkable coincidence that we live on a planet with a moon just exactly the right angular diameter to eclipse our sun [in fact it is so exactly right that we have both total and annular eclipses], here is my theory about why it less surprising than it otherwise appears to be.

I am also interested in politics (who isn't). In a referendum on 5th May 2011, the British electorate rejected the alternative vote system, which isn't truly proportional anyway. I thought about it and devised a truly proportional system which preserves the link between MP and constituency, which British voters (rightly) consider important. You can read my thoughts about it here.

I also like to bake. Here is my shortbread recipe.

All the following links are references to other web sites:-
Derivation of the 1964 colorimetric standards
Unit Testing Techniques and Tool Support

[ Contributions to "The Last Word" in "New Scientist" ]
Out of the blue 27 September 2017
Round the Bend 18 April 2018
Blow out 24 October 2018
Superstring theory 14 November 2018

[ under the pseudonym 0 ]
Computer Recreations ("Napoleon" or "The Military Game")
Computer Recreations ("MOO")
Computer Recreations ("Kalah")
Computer recreations. Space-filling curves, or how to waste time with a plotter
Computer recreations. ("Darwin")
Computer recreations. April Foolery
Computer recreations. By midsummer madness, or how to waste more time with a plotter

Here are a few other web pages that reference me, to save you searching:-

You can contact me by email at "aleph0hpela-bew19 yahoo co uk" with the obvious (at least to humans) insertions. I'm sorry not to give an address that you can just copy and paste, but I do not want it harvested and used by spambots. If nevertheless I get too much spam on it, I will change it, so if emails to me suddenly start failing, look again at this web page to see what the email address has changed to.