Technical Support

The creator of the Pringles can gets buried in a Pringles can.

Don't worry, he was dead at the time....

Saturday Night, and Sunday Night

I went observing at the MMTO for four nights last week, just in time for an unusual low system to come down and give SNOW on the mountain in May. In Arizona.

To add annoyance to irritation, we were clear on saturday and sunday night, but of course.... the wind was too high. The chart from the automated weather station is shown above.

The Zamboniscope

It's a bad sign when you can make Roger Angel laugh out loud at your idea.

In a conversation with James Lloyd from Cornell at the Spirit of Lyot conference in 2007, he'd mentioned a novel way of making a space-based telescope using an old idea called a "luneberg lens". The lens is a sphere of matter, with a certain monotonic gradient of refractive index that varies only with radius, i.e. n=n(r). If you place a camera on the surface of the sphere and look back through the center of the bubble, you form an image that is free of spherical aberration and many other low order terms.

Lloyd's idea was with trying with a gaseous diffuser - initially, the gas flies off at the speed of sound determined by the temperature of the gas, but if you constantly replenish it from a compact source, maybe you could attain a steady state and have a large, very long focal length lens floating in space. Thinking further though, there is a simple case which shows that this doesn't work - when we look at distant stars passing behind the atmosphere of nearby planets, very little refraction of the the star is observed. So, even with approximately 1 STP of atmosphere, the focal length of such a system is ludicrously large.

Okay, so that doesn't work.

But.... what about a liquid or a solid?

I vaguely recalled that there is an under ice experiment in Antarctica that uses strings of photomultipliers, melted and subsequently refrozen into place in the antarctic ice many hundred of meters far below. Surely there was some measurement of the transmission coefficient of this ice?

Sure enough, there was! And the numbers in the paper blew me away - the mean free path for visible/blue light is about 200 meters - yes, that's right, the ice is so free of scattering microbubbles that you can see for two football pitch lengths.

Adding to this, it turns out that this is several times clearer than any ice made in a laboratory. The purest ice in the world appears to be about 1000m below the surface of Antarctica.

So, if you can manufacture a sphere of pure ice, which is then doped with a chemical that provides the index of refraction change in accordance with the Luneburg formula, you're good to go.

How big a lens can you build? Well, since we are in the realm of fantasy here, I thought I'd be conservative and go for 500m in diameter. After a quick bit of algebra demonstrated to me that the optimal size for an Ice lens is on the order of the absorption length (the exponent in the absorption quickly clobbers the effective surface area of the lens with increasing diameter), I also came up with a way to do the metrology. Get your sphere to within 1cm of the ideal sphere, and then use a reflective ball bearing in the center to act as a reference mirror, and then have machines that trundle along on the surface of the lens, peering down through a liquefied section of the ice that is melted by a surrounding hot plate.

Hmm, a machine that melts rough ice into a smooth surface. Where have I seen those before? Ah, at the ice hockey games!

Yes, I've invented the Zamboniscope.

No wonder Roger laughed at me.

The London Underground

The London Underground map is one of the most elegant pieces of design in the world, and is a great demonstration of topology too. Geographical distances between stations are sacrificed for clarity in showing the relationship between the different train lines and their stations.

But what does the tube map look like when placed on a geographical map? Simon Clarke in 2000 produced the map below. Simon's original pages seem to have disappeared, so I've taken the original image I saved years ago and put it here.


I'm not alone in admiring the quirks of the London Underground, so Geoff at geofftech.co.uk has produced a wide array of different versions of the well known maps.Owen Massey has a very thorough collection of tube map links that have distracted me no end.

"No astronomy please, we're British!"

In one of the most spectacular own goals in science, politicians have decided that pulling out of Gemini is a sensible cost cutting measure for British science. Of course, cutting all British astronomers out of a northern hemisphere large aperture telescope might have caused some heated debate - so it was done without consultation with any of the astronomers.

The fiasco is being followed in close detail over here.

By terminating our support contract several years early, Britain demonstrated that they weren't to be trusted in large international collaborations - in addition to making trivial cost savings, the STFC had the steel cojones to ask to be kept in Gemini but at a reduced level. Gemini (quite rightly) told Britain to go take a long walk off a short pier.

OnStarrrgh

Back in March 2006, a friend took me auto-cross racing. There's a drag racing strip south of town, and the car park for spectators is turned into a quarter mile set of sharp corners and narrow chicanes with some judiciously placed orange cones. Over the course of six hours, there are four groups of racers. If you race in one group, you have to carry out a marshaling/support job in one of the other groups - in this way, they can have a full set of people watching for run-over cones and violations of racing protocol.

In each group there are about 30 cars, and each car starts off every 30 seconds around the course which takes about 40 seconds to travel around, and when you finish, you can go to the back of the line-up grid for three more runs in your group. In this way, almost 500 timed races are carried out with great efficiency.

Unfortunately, it means about 6 hours waiting for at most 8 races around the track - sitting in my friend's tricked out Subaru, though, it was excellent fun and I could clearly see the draw for those with the passion for it.

In the last group though, one car looked distinctly out of place. Amongst the street race cars and turbos, there was a large tank of a town car. It was coloured pale brown, and would not look out of place in a retirement community with some blue haired old woman peering over the wheel. The car ponderously pulled up to the starting gate, and did its best to screech off around the course. The crowd watched as this slow tank of a car pitched over like a drunken soccer mom around the curves and attempted to burn rubber on the sharper of the corners. Halfway around, however, the car slowed down suddenly, and completed the course at almost half the speed it started with. The crowd murmured amongst themselves - what had happened?

The answer came soon enough - the auto-cross drivers had rented the car from a local agency to take it auto-crossing, and halfway around the track, the OnStar emergency service intercom crackled to life, with a service person enquiring if they had been in an accident, and were they alright?

Apparently their driving was extreme enough to set off the acceleration sensors dotted around the frame of the car.

Memo to self: do not buy rental cars.