"visible from space", and "visible from the moon" are two different things.
Space starts at around 100 miles up. The Moon is a quarter of a million miles up.
The great wall might be visible from 100 miles up, but other man made stuff would be more visible.
I thought about the shadow factor making it more visible.
If it ran north-south it would cast a mourning, and an evening shadow that would amplify its image from space.
Two problems- highways attract businesses and other construction which amplify the width of the road when seen from space.
Even if you couldnt see that actual pavement you could see the line of shopping malls that flank the highway on either side and which amplify its cut through the countryside even more than a shadow would amplify the size of the great wall.
the other problem is that the great wall runs east-to-west so it casts most of its shadow on to itsself.
Intresting point about the aral sea. However its not "whats left" of the Aral sea thats manmade. Its the parts that used to be there that arent there now that are "man made"(ie the new land were there used to water).
I thought about manmade waterways- canals.
Resovoirs can be quite large- lake mead, and the future lake that will form behind the seven gorges damn in China would both be atleast as visible as the panama, and suez canals, if not more so.
BUt manmade land could also qualify.
The Dutch deliberately made land out of seabed to fatten thier country.
At the same time humans accidently obliterated much of both the aral sea, and Lake Chad,- like the dutch- turning blue water into biege dry land. These expanses of dry land are - i dunno- hundreds of square miles. They may excede the size of the biggest resovoirs, and may indeed be the biggest and most visible manmade "objects".
13 May 2009, 10:16 pm
