Which planet am I on?

The latest issue of New Scientist magazine reviews a new book, The Pluto Files: The rise and fall of America's favorite planet. The author, Neil deGrasse Tyson, wasn't directly responsible for the demotion of Pluto from planetary status in 2006. But after installing a new Pluto-free display of the solar system in New York's Hayden Planetarium, where he is director, he received hate mail, and evidently decided to cope with it by writing this book.

Well, anyone who's cycled from York to Selby, or from Taunton to Bridgwater, has proof of Mr Tyson's folly. Both cycle paths have scale models of the solar system, and both feature Pluto as fully-fledged planet. So it must be.

The York-Selby route is the world’s second longest cycle path. To scale, anyway: at 1 in 575,872,239, it represents a six-billion-kilometre-long rail trail. It begins just under the ring road south of York, with a 2.4m diameter golden globe representing the sun, and finishes 10.3km away just outside the village of Riccall with the tiny 6mm sphere that represents Pluto (right). En route you have all the planets, sized and placed to that scale.

It vividly illustrates the emptiness of space, very different from the crowded celestial pool table suggested by your school textbook. Though, granted, as you strike south away from the sun, things start off relatively congested. Mercury, the size of a ball-bearing, is 101m from the sun. Venus, slightly larger, is 87m on. Another 72m brings you to Earth, a bright blue gobstopper splendidly painted with continents and oceans. Mars, a vivid crimson pea, is 136m beyond.


Jupiter, swirly and as big as a football, is over a kilometre on; Saturn, adorned with its rings, is a similar distance past that. To reach grapefruit-sized Uranus (right) and Neptune you have to go another 2.5km and 3km respectively. If you think the name of Uranus is bad enough, it could have been worse: when William Herschel discovered it in his back garden in Bath in 1781, he wanted to call it George.

Finally comes Pluto – or rather ‘134340 Pluto’ as it is now officially known, following its relegation in August 2006 to the minor league of planets along with other distant orbital chaff such as 90377 Sedna, 136199 Eris, and 50000 Quaoar. But it must be a planet because here it is, just outside the village of Riccall, along with its satellite (or rather, planet twin) Charon.

Each is as big as the sort of thing that falls out from inside your bike during some ambitious piece of DIY mechanics and doesn't appear to fit anywhere when you try to put it back. You just can't imagine how something so small and so far could possibly be detected from earth, the size of a mouse trackerball 11km distant, especially when it's only illuminated by the sun, back on the A64 by-pass.

But if Pluto seems remote, consider that on this scale our nearest stellar neighbours – the Alpha Centauri family – would be 70,000km away. Space has an awful lot of not very much. But then Selby could well be full of Dark Matter.

As if that wasn't enough proof for the planet-denying Mr Tyson, there's TWO more Plutos on the Taunton-Bridgwater canal in Somerset, a canal which has a double set of scale-model planets along its length, and which somehow manages not to be linked to the rest of the waterway system.

In this case the sun is halfway between them, at Maunsel Lock (where there’s a Canal Centre; OS 193, ST309298). The canalside orrery has a double set of planets, ranging out from the sun in each direction. So, to scale, it’s even longer than York’s.

It’s 23km along the canal from the Bridgwater Pluto to the sun and beyond to the Taunton Pluto, which has placed the now-relegated planetoid in the decidedly non-league location of a supermarket car park (right). Pluto, which as any fule kno is A PLANET, wasn't discovered until 1930; well, they should have looked here.

There's quite a bit more about these routes and other similar ones, including how-to information, in my book (see left).

Here's a Google map of the York-Selby route:


View Larger Map

Not especially London-centric, I know, but I couldn't resist it, and it's worth trying to snag a cheap rail deal to York to do this path. And tomorrow's post will be very London, I promise.