h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

OK, so the Great Wall of China and the M25 are visible from space (presumably this means with the naked eye from an orbiting spacecraft, say at Mir height)...what else? I seem to recall that the Fresh Kills Landfill (Staten Island, New York, USA) is the largest man-made structure in terms of sheer volume. Does anyone know whether this factoid is actually the truth?

This M25, Great Wall thing always bothered me somewhat. If you can see the M25 why not the M60 (Manchester ring road) or the M1, or any other motorway, domestic or foriegn. Heathrow airport must be a pretty good contender as well, as too must the Millenium dome judging from its appearence in the Eastenders titles. I'm just waitng for an actual person in space to call me up on the phone and say 'hey ric I can see your house from up here'

regards etc. etc.
ric

Well, of course, some of us Yanks have seen our houses from space courtesy of Terraserver (http://www.terraserver.com), though, sadly enough, my current place is not in their coverage area. I guess the Russkis never wanted to bomb a bunch of wheat fields badly enough to take pictures.

I read somewhere that you can't actually see the Great Wall of China from space, only it's shadow when the sun is at an acute angle. I assume we are talking about using the naked eye, not one of the surveillance satellites that can read your underpants label from somewhere in the region of Ursa Minor. That being the case, there is no way you could actually see the M25 from space. When I say the naked eye, I'm obviously assuming you're actually in some sort of spaceship otherwise you'd be a bit too busy to admire the vies let alone phone anybody up to say,"Hey! I can see the M25 from up here and I'm not even using binoculars!"

Absolute pants.
If its visible from space why isn't it visible on the weather pictures?

Well the M25 is visible from my space, it's only a 15 minute walk away. I have to cross it on a pedestrian walkway bridge to walk in a country park.

Here's a 1:200,000 aerial photo of the area where the M25 meets the M4 (also the area of Heathrow Airport). You can clearly see Heathrow Airport but it's very difficult to make out the route of either motorway. (You can put the cursor over the aerial photo to see the map.)

http://www.multimap.com/map/photo.cgi?client=public&X=500000&Y=180000&scale=200000&width=500&height=300&gride=&gridn=&lang=&db=&coordsys=gb