There are many good reasons to visit Ruislip Lido. For a start there's the lido itself, a 60 acre reservoir built 200 years ago for the express purpose of feeding the Grand Union Canal. There's a proper beach, a sprawl of sand ideal for family fun in more clement weather. There's the excellent Ruislip LidoRailway, Britain's longest 12-inch gauge line (which will be open daily from Boxing Day to New Year). There are Ruislip Woods, the largest block of ancient semi-natural woodland in Greater London. There's a cafe. There's a carvery. There are hundreds of ducks. And now, as if all that weren't somehow enough, there's an entire solar system.
You know the kind of thing. A small model in one particular location marks the position of the Sun, then other smaller models in other locations mark the relative positions of the planets. There's a rather good example in Otfordin Kent, another along a canal in Somerset, and another along a disused railway near York. But there isn't one in London, or rather there hasn't been one before, until Hillingdon Council and the West of London Astronomical Society stepped in this summer and provided one.
The Sun is located at the south end of the lake and Neptune at the other, which defines the scale. That scale is four and three quarters of a billion to one, which is quite some squish, and places the two extremes just under a kilometre apart. What's more, there really is a Sun, it's a yellow ball raised high on a pole near the new boathouse, and just under 30 centimetres in diameter. Immediately underneath is an information board, jam packed with facts and recent images. And a few steps away is a telescope, installed a while back with Lottery funding allowing visitors to squint down to the far end of the lake. "Do Not Point At The Sun", it says, although the new one's perfectly safe.
The designers have then drawn several imaginary concentric circles with appropriately calculated radii, looked to see where they cross the path round the edge of the lake, and placed an information board at each location [map]. Half the planets are very close, within direct sight, lined up on the top of the dam. It's only twelve metres to Mercury, for example, then ten to Venus and nine to Earth. This time there are no models, they'd be too tiny, but the information boards remain excellent. They're written in child-friendly language, but without being patronising, and are full of facts and full-colour photos. If you have small scientists in tow, they'll be engaged.
A particularly nice touch is that each of the planets has its own dedicated webpage, and this features a subtly different descriptive passage. You've got to love the fact there's a page on the local council website called hillingdon.gov.uk/mars (and coming up later, even better, hillingdon.gov.uk/uranus). As an added bonus an mp3 file of the spoken text is embedded so you can play that, either in the comfort of your own home or whilst standing in position by the lake. You don't even have to live in Hillingdon, you simply need to be interested in our solar system.
What follows, up the remote wooded eastern bank of the lake, is the first proper inkling of the scale of the Solar System. The walk to Uranus takes considerably longer than you're expecting, even based on the rate the gaps between planets have been lengthening thus far. Even when you think you've finally spotted the next board, it turns out to be merely reassurance that there will be another planet soon and you should keep going. Eventually Uranus pops up, close to the railway's passing loop, the board revealing its image as a disappointingly featureless blue disc.
It's almost as far again to the next planet, thanks to a wiggle in the path. The planets have all been located on the edge of the lake at the correct scaled distance from the Sun, so don't lie in a direct straight line, indeed it would be a fantastically unrealistic state of affairs if they ever did. An intermediate board about comets has been added for interest along the way, not specifically Halley-related, but positioned at the approximate farthest extent of its orbit.
Ultimately you'll reach Neptune, maybe twenty minutes after starting out, at the very top end of the lake where the footpath squeezes right up against the railway. There's no Pluto, because Pluto isn't a planet any more, and it'd have to go in the middle of the golf course if it were. But there is one final information board to remind you of what else lies beyond in the vast realms of deep space... into the unknown. We're told that Alpha Centauri would have to be in San Francisco, for example, with Barnard's Star in Hawaii and Sirius in Brisbane.
Hillingdon's 'Walk The Planets' trail is a marvellous idea, well realised, and still at the stage in its early life where all the boards are pristine and legible. Much credit too to the West of London Astronomical Society, who might even get some new members out of this, either now or grown up in another ten years' time. Meanwhile it's not that Ruislip Lido was ever lacking a number of good reasons to visit, but now there's another.
