Prime real estate

We were walking round the back of the O2 in Greenwich today and saw this artwork marking the Greenwich Meridian. I wondered why there seemed to be several different lines marked on the ground, one of which had some white metal or plastic extensions (containing a light, I assumed) stretching over the edge of the path and over the water. Behind the fence in what is now the back of a hotel I could see some stores let into the ground with names of different countries, and assumed (correctly it seems) that these are poorly-maintained markers from the millennium just a few years ago.

The Prime Meridian in all its glory

The Greenwich Meridian web site is very useful here. It turns out that there are many different possible meridian lines. The one that is usually marked is the Airy Transit Circle, the main one that runs through the Greenwich Observatory, though it’s not the line shown as 0 degrees longitude on a GPS device, and it actually no longer has any connection at all with the UTC time standard.

As well as the Airy Meridian, three other Lines were marked [round the back of the Millennium Dome] – the Bradley Meridian, roughly 6 m to the west and still used by the British Ordnance survey, along with the rather spurious ‘Halley’ and ‘Flamsteed’ Meridians.

This article explains in some detail why when you visit the ‘Prime Meridian’ at the Greenwich Observatory, your GPS locator does not read 0 degrees of longitude – you’d need to move some 100 meters East:

zero degrees my ....

If you’re feeling overly joyous and need a downer, read this account of the doomed Millennium Tree Project.

The prime meridian hasn’t fared particularly well in my neighbourhood either. I hadn’t even realised it had been marked out in an artwork in Hither Green, but it’s all but vanished now.

estate office
There was a stone marking the place where it crosses Lee High Road (close to where the photo above was taken) but I went looking for it yesterday and couldn’t find that either – possibly because they’re digging the road up. I hope it gets put back.

All of which leads me to think that meridian lines are really quite silly, arbitrary things. A bit like New Year’s Eve or Millennium night itself…

millennium night

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Are we all meant to be racist now, Father?

I have a confession to make: I am a bigot.

Let me explain. I voted Remain in the EU referendum and was angry, upset, dismayed, asthmatic at the result. For me it was a binary choice, the ballot paper looked like this:



This view, and the way I voted has its roots not in urban or student politics, but in a Church of England primary school in North Somerset in the early 1970s. I can remember being told in assembly by our head teacher Mrs Hutchcroft that we should treat people the same regardless of the race, colour or creed. I had to ask what ‘creed’ meant.

Ours was an almost entirely white village, aside from the family who ran the Chinese takeaway. Even my secondary school had, when I was there, ONE black pupil, and even then only temporarily. So perhaps it was an easy statement for my head teacher to make. But her words stuck with me, I can even picture where I was sitting cross-legged in the hall and the smell of the varnish and school dinners.

Stunned yesterday by finding myself one of the 48%, I concluded that 1 in 2 of us in this nation is just not a very nice person, possibly racist. It was a binary question that revealed our view of ourselves and what kind of country we want to be.

People are saying we need to ‘reach out’ to the 52% and understand them. But what if I think they are wrong? What if I refuse to accommodate racist, inward-looking views? Why should I? I feel like the residents of Craggy Island asking Father Ted “should we all be racists, now father?”

So why am I a bigot?

Dictionary definition:

having or revealing an obstinate belief in the superiority of one’s own opinions and a prejudiced intolerance of the opinions of others.

That’s sounds like me.

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First week class teaching BBC microbit – reflection

I’ve introduced 3 year 7 classes to the BBC micro:bit this week – here are some thoughts.

  • Organise your kit. I strongly recommend individually numbering each micro:bit, especially if you are keeping them in school in term time, and logging which pupil has each device. This will save arguments if they are lost or damaged and they’ll get their code on the micro:bit next lesson.
  • Allow plenty of time for packing away. The supplied boxes seem to prove a challenge for many Year 7s, though mine were getting better by the end of the week. Get a bigger box? Also, keeping track of the USB leads is going to be a challenge. I can see these getting lost.
  • The Technology Will Save Us demo supplied on each device is a great opening lesson. I used it to familiarise the pupils with the handling requirements, they didn’t even need to log in, just turn their computers on to provide USB power.
  • They want to take them home. But the micro:bits are so late arriving we will only get 3 full lessons out of them – some sets will only get TWO! Part of me wants to hold on to them and let them next term (in Year 8) get proper use out of them and take them home at Christmas. What is anyone else doing? Did the BBC want them to be used for only 2 lessons in class?
  • I have had a lot of failures with demo units – so far, as far as I know, only 1 died this week. It was mine. I was demonstrating it in front of the class and it utterly died, about 5 minutes after I plugged it in. I was handling it carefully – indeed that’s what I was demonstrating. I must be cursed!
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First whole-class micro:bit lesson – reflection

I did my first whole-class lesson with the BBC micro:bit in a Year 7 class today – here are my impressions.

It was a very short lesson so I just used the Technology Will Save Us demo that comes on box-fresh micro:bits as a starter to allow Year 7s to get to grips, literally and metaphorically, with the device.

I gave a LONG talk about safe handling – you can see my slides here – and explained that I’d had several fail because of static shocks given to them by children touching the gold pads on the back of the A button when they are plugged in.

I then gave the pupils USB extension leads to unravel and plug in (our base units are buried inside their desks, and the supplied micro:bit leads are far too short) and got them to plug the micro:bits in to the extensions and see what happened.

There was a very mixed response in this group. I gave minimal input, I just wanted to see what they would discover – some sailed though the demo so quickly I had to give them the heart easter egg to unlock the Snake game (you knew about that, right?).  One girl was frozen in terror by my safety lecture, too scared to push the A button.  A few got totally foxed by Chase the Dot – they needed others to tell them to tilt the micro:bit, though when I quizzed them after, they ALL said they’d played iPhone / iPad games that you tilt to play. We had a discussion about what an accelerometer does, and one girl said “is it a sensor?” which led on to talking about other things the micro:bit can sense.

I have to say I think the handling requirements – earth yourself, don’t touch the back when it’s plugged in, hold it by the edges – are unrealistic. Despite my dire warnings, I saw several violations. It’s really hard to give kids a new toy with shiny lights to explore, then expect them not touch the back when pressing the buttons (which really is the natural thing to do).

Next time we will do my Python intro lesson using the excellent standalone Mu editor. I found that the Microsoft Block Editor does not work at all well on our Virtual Desktops, and Nicholas Tollervey kindly did lots of work with us to get Mu to work well with the Citrix VDI. It makes transferring the code to the micro:bit much simpler than the browser-based coding platforms. You just click the ‘flash’ button and it copies it across.

The other huge challenge which I did not allow enough time for was packing them away. I have numbered each device and made a note of which pupil has each unit. This is partly because I am keeping them in school for now and I think it’s best they have the same unit with their code on. Also it’s to try to avoid arguments if they break. And I have had a high failure rate in testing, so I am braced for this possibility.

Already several pupils have asked about having them at home in the summer, which is great, but I have mixed feelings. They arrived so late, and we have trips and all sorts going on this short half term, we will be lucky to get even 2 or 3 full lessons out of them. I kind of want to hold on to them and teach more in the Autumn term with the same pupils, who will then be in Year 8, and let them take them home at Christmas.  I can’t see them all coming back to school after the summer hols…  one to ponder.




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Wireless remote data logging with the BBC micro:bit

I was quite astonished to stumble upon this today – it really is relatively simple to use use the BBC micro:bit to log data remotely, indeed wirelessly.

The micro:bit can log several kinds of data including accelerometer readings in 3 dimensions, magnetic force readings, light levels, compass bearings and temperature (this is I think internal to the board, but may be indicative of the environment).

Here’s what you need:

  • 2 BBC micro:bits, one to act as the logger, one as the receiver.
  • A computer with Python and pySerial installed.
  • A battery pack for the logging micro:bit.

I used a MacBook that already had Python 3 / IDLE installed on it, though I had to install pySerial following the instructions here:

I then followed the instructions here:

You put the same code on the logging micro:bit and the receiver.  This uses the Microsoft PXT platform. I found the PXT editor didn’t work properly in Safari, so I used Firefox instead. I also tweaked the code so it logged more than just the accelerometer readings (see below).

You compile the code in the web-based editor, download the HEX file and drag it onto your micro:bits.  Send one of them off on its way with a battery pack, and keep one plugged in to your computer.  Then you need to run the Python script on your computer – this collects data and writes it to a CSV file which you can open in a spreadsheet program like Excel or Open Office.  I think it might be better to log time before the other data, and it would be nice if the Python script displayed some data as it comes in – I thought it wasn’t working, as the micro:bits don’t light up as they are running.

My script logs loads of data so I sorted it in Excel and then made some charts to show temperature changes.  See if you can spot when I breathed on it, and when I took it outside:

And from the light levels when I put it in the cupboard under the stairs, and when it went outside:

I can see plenty of uses for this as the micro:bit devices themselves are relatively inexpensive – science experiments spring to mind.  Attach other sensors? Could this even be the basis of a weather station? Attach one to a robot, a drone, perhaps even an animal?!  I’m not sure what the range is, but it’ll be fun finding out!

Here’s my tweaked code that logs way too much data:

// By Andrew Mulholland -
// Simple example to go alongside the Python script for reading data wirelessly using 2 BBC micro:bits.
// Transmits the 3 accelerometer values alongside a title to allow them to be distinguished later.
// When they are recieved on the other end, simply write to the serial port to be picked up by the Python Script.
// Script was written with the Microsoft PXT platform, it can also be found at

// If copying below into PXT code section, ignore all comments and copy from line below.

// tweaked by @blogmywiki

basic.forever(() => {
    radio.sendValue("Acc-X", input.acceleration(Dimension.X));
    radio.sendValue("Acc-Y", input.acceleration(Dimension.Y));
    radio.sendValue("Acc-Z", input.acceleration(Dimension.Z));
    radio.sendValue("Compass", input.compassHeading());
    radio.sendValue("Magnetic force", input.magneticForce(Dimension.Strength));
    radio.sendValue("Light", input.lightLevel());
    radio.sendValue("Temp", input.temperature());
radio.onDataReceived(() => {
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