Originally Posted by Ephor
Having done little research into the way the human eye perceives the light that bombards it, I was left rather stumped by a question posed earlier in the day.
Why is the Wall of China the only man-made construction visible from space* when other constructs with a presumably greater width (perhaps the Millenium Dome? There are better examples I'm sure) are not?
Thanks for helping me help you to waste our time. It's been an experience.
*I apologise if this is a myth.
There are varying reports as to whether it is a myth or not, but in answer to your question, I would imagine it is because it isn't the width that you see from space, it's the length. It would be like a line trailing across the land.
Something like this
, handily snapped in false colour by a shuttle astronaut in 1994.
You can't see the milennium dome with the naked eye from space because it is essentially a tiny white blob in the centre of a big grey city. You can't see the great pyramid of Giza with the naked eye from space because it's essentially a tiny yellow square in a big yellow desert. They have no significant impact on the top-down view of the land they were built in, whereas the great wall does - it would perhaps be more accurate to compare the ability to see the wall from space with the ability to see the Nile from space, in that respect (and to any potential pedants I'm aware the Nile isn't man made