Keep hearing that the Great wall is visable from outer space, but then I have heard that isn`t true at all. Any comments?

I'll let you know the next time I go up.

Not true! Even the Chinese astronaut said he looked for it but couldn't see it. Wish I knew how the myth started!

k

The width of the wall is only about 5m. It'd be impossible to see from 400,000m out.

Myth.

Hanuman, are you going up with Steven Hawkins?

I think the smallest man-made "structures" visible from orbiting spacecrafts are Chek Lap Kok Airport in Hong Kong and Kansai International in Osaka. I guess the new Chubu Airport at Nagoya should qualify too.

Chubu is about 4,000m x 2,000m in size. Kansai and Chek Lap Kok larger.

Just came back and took this picture for you - http://www.nasa.gov/images/content/1...8497arrows.jpg

Arrows point to where you can see the great wall.

Seriously here's a nice little article by nasa - http://www.nasa.gov/vision/space/wor...reat_wall.html

Sure it is visible from outer space - with a telescope.

Here's a picture I took from CO98 HKG-EWR, just NE of Beijing. I was actually trying to look for the Great Wall, but somehow I couldn't. But I think at this altitude (32,000ft, or just under 10,000m), the Wall should be just visible with the naked eye.

rkkwan.zenfolio.com/p476976649/?photo=720955459

This is taken with a 50mm lens on a 1.6x crop camera, so equivalent to a 80mm lens on a 35mm camera; the photo is also slightly cropped, so I'd say perhaps equivalent to 100mm.

Again, this is at 10,000m above sea level. (The hills are about 600m/2,000ft). The Space Shuttle usually orbit at 300,000 to 400,000m. 30-40x the distance.

In most places, the wall is only as wide as a country road. Some 10-lane L.A. freeways would likely be more visible than the Great Wall!