Bits and Pieces: Left Turns

The research at U.P.S. is paying off. Last year, it cut 28 million miles from truck routes — saving roughly three million gallons of fuel — in good part by mapping routes that minimize left turns.

Incredible – something that seems obvious in retrospect, but in practice hard to implement. Interestingly, it wouldn’t work in the UK, since you have to stop at red lights whichever direction you’re turning.

Also, a couple of good passages from the book on weather I’m reading:

When sunlight hits the atmosphere, the light waves are scattered in different directions by dust particles and air molecules. The shorter violet and blue waves are scattered more effectively than the orange and red ones. The effect is similar to what happens when ripples in water encounter a swimmer: small ripples are deflected while large waves continue past the obstacle undisturbed.

A mixture of violet, blue, green, and tiny amounts of the other colours is scattered across the sky. The combination of these colours is blue. The exact shade of blue will vary according to the amount of dust and water vapour in the air. Water droplets and dust particles enhance scattering, increasing the amount of green and yellow and turning the sky a paler blue.

This is why the summer skies of densely populated European countries seem paler than those of vast, sparsely populated areas such as Australia and Africa.

This is one of the clearest, most concise explanations of ‘why is the sky blue’ that I’ve seen yet. Not only does it explain the science in full, not only does it give a very visual and accurate analogy with the swimmer, but it also explores the consequences of the explanation in a way that will be immediately familiar. This is in stark contrast to the ‘explanation’ proffered by the Guardian, ‘A daytime sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light,’ which explains nothing.

Meteorologists distinguish between skill and no-skill forecasting methods. If we consider rainfall prediction, two basic no-skill methods appear to give impressive results. The first is the persistence method, which is simply forecasting tomorrow’s rain to be the same as today’s. In middle latitudes, this typically gives results of about 70% accuracy, but of course fails to predict changes.

The other no-skill method, the climatological method, uses long-term averages. If, for example, the statistics for a particular location show that during January there is an average of 10 rainy days, then we would forecast rain every third day. Our forecasting accuracy would again be about 70% for many middle-latitude locations.

These methods take no account of the actual weather. For a forecasting technique to demonstrate skill, it must be more accurate than these no-skill approaches.

For some reason, it pleases me to know that you can reach a 70% accuracy in weather forecast simply by saying ‘tomorrow is going to be the same as today’. It makes me understand how priests and shamans could get away with their predictions.

Bits and Pieces: Centuries


In a book about weather (called ‘Weather’) that I’m reading, there’s a fact that blithely states:

Driest location: The Atacama Desert in Chile has virtually no rainfall (0.08mm annually), except for a passing shower several times a century.

Not several times a year. Several times a century. What impresses me about this is not the fact that it’s a dry place, it’s that records exist to the extent that meteorologists can say this with confidence.


I’ve been selling a bunch of games on eBay lately, and I have to say that it’s really improved. The last time I sold something on eBay was several years ago, and the entire experience was unpleasant, from listing the item, to writing the label, to queuing in the post office. It wasn’t something I wanted to repeat, so I didn’t.

In the meantime, I was always amazed by the fact that several hundred thousand people in the US alone make their livings over eBay. How were they not driven into a murderous rage by the clunky interface and the all the other attendant irritations? The reason, it seems, is because the selling interface is really pretty decent now. What’s really cool, though, is a tool that lets you automatically buy postage – with the correct address already on it – and print it out at home. Given my long-standing hatred of the post office, I really appreciate anything that lets me avoid the place. It’s not a particularly sophisticated tool, I suppose, although it did need eBay, PayPal and the Royal Mail to all work together. In any case, it’s not the sophistication that matters, it’s the result. Well done eBay!

24 hours and 39 minutes

That’s the length of a day on Mars. What you’re thinking is probably, ‘huh, why is it 39 minutes longer than our day?’ But what you should be thinking is, ‘wow, why is it so close to our day?’ The fact is, there’s no reason why it should be close: the day length on Venus is 243 (Earth) days, which is 18 days longer than the time it takes to orbit the sun. I don’t think anyone knows why it’s so close, but it is certainly convenient for anyone who wants to live there.

The Mars Society has a base in the Arctic that is an ‘operational’ simulation of a base on Mars. Long-time readers will know that I spent a couple of weeks at a similar base in Utah a few years ago. Since the base in the Arctic is 75 degrees north, and it’s currently summer, the base is basically in eternal sunlight. By blacking out the windows at appropriate times, this means that the inhabitants of the base can effectively simulate living on Mars time. The question is, will the people at the base be able to cope with their usual routine (e.g. collecting rocks, conducting experiments, etc) without suffering any number of ill effects? And will Mission Support be weirded out by the time on Mars apparently slipping forward by 39 minutes every day? That’s what makes this (apparently unprecedented) experiment so interesting, and I’ll be waiting to see the results.

Rock Band

While writing this post, Firefox suffered a bizarre semi-crash that stopped it from talking to the Internet and then lost everything I’d written. Let me just say that while I love Firefox, it clearly has some real issues. To calm myself down, here’s a video of Rock Band, the spiritual successor to Guitar Hero:

Say what you like, but one thing’s clear: those guys are rocking out. So come Christmas, when the games released, I’ll definitely be buying it. Along with a 360 or PS3 – whichever has the least rubbish lineup by then…