Prime numbers and multiples of six...

There you are happily wandering through the pre-Christmas melee when, out of the blue, something of a revelation hits you right between the primes.

We, my nine year old twins and I, had spent the day chasing Christmas trees, writing cards, sorting out the lights and all those other festive bits and pieces. Lacking energy, I caved (well it didn't take much to be honest) and agreed to chips for tea. Added the compulsory greenery and we sat down to tea with the usual demand for a quiz (sometimes its our version of Twenty Questions...). Anyway Megan's chosen subject: Maths.

Mum invents the questions and to get to the point, a discussion ensued on how to identify whether or not a number is prime. Caitlin asks: "Is three billion and 1 a prime number?" I can't answer in the time available (Strictly Come Dancing is going to start soon). Then Caitlin announces that, apparently, all prime numbers are either one less than, or one more than a multiple of six. Therefore, it seems, that you can at least say that a number is not prime if that requirement is not met.

They all rushed off to watch the semi final - the maths of the SCD quarter and semi finals is another story - leaving me to discover that this multiple of six thing is true and to wonder why I had never heard that before. Maybe it's just me that it has passed by or that has passed it by...

Nine year olds...hah!

Why do car wheels have an odd number of spokes...

Sitting in a car park yesterday I was elevated in a moment of meditation to notice that the wheels on every# car I could see had an odd number of spokes.

Five spokes and seven seemed the most frequent but there was one with three spokes. There were none I could see with four, six or eight. Googling revealed this article which sort of discusses the axes of symmetry of a Ferrari wheel (five spokes) but only refers to the aesthetics rather than there being any engineering rationale behind the oddness.

A Google images search seems to indicate that odd is by far the overwhelming favourite for spokes but not exclusively so. It would seem that eight is not uncommon among what seem to be high-performance cars (those that are involved in high speed racing for example). Thus maybe it is just aesthetic. It would be interesting to hear what others think.

Event calendar now up and running

After a few trials and tribulations involving sending data from the calendar through Yahoo's website for processing and back to our Calendar web page the processing of event information now works. What was the problem? Well...in order to display the map of events it was necessary to extract the address information and encode that in a form for Google maps. Bizarrely, however, Google doesn't do that, but Yahoo does - through its data 'pipes' system. The data gets fed back to Google maps automatically allwing the bat indicators on the map to plot all the events that have sufficient information in them for Yahoo to pinpoint the location.

It's all very cunning and not a little mind boggling. But, hey, it works...

At the top of the page is a link to a form with which you can submit your event. It has to go past my eyes first however in order to avoid nonsense entries etc.