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Ephor 6 Oct 2005 05:18

The Great Wall of China
 
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.

Mushroom 6 Oct 2005 05:55

Re: The Great Wall of China
 
Quote:

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 :rolleyes: )

KoeN 6 Oct 2005 07:46

Re: The Great Wall of China
 
because it is a myth.

Belgarath The Sorcerer 6 Oct 2005 08:23

Re: The Great Wall of China
 
http://www.snopes.com/science/greatwal.htm

Appocomaster 6 Oct 2005 10:04

Re: The Great Wall of China
 
That's disappointing. You could have spelled out some really great messages over Russia to send messages to space.

acropolis 6 Oct 2005 12:20

Re: The Great Wall of China
 
Despite the technicality that this is all based on an untrue fact, i'd like to comment.

I've noticed that I can see electrical lines from upwards of miles away. They are probably less than an inch thick, and yet i certainly can't see anything 1 inch X 1 inch from anywhere close to that far away. I'm not going to guess about why that is, but I would say that were the situation similar you should be able to see the great wall (assuming 10 feet width?) from (assuming 0.5 inch wire at 2 miles) 240 X 2 = 480 miles. Which is outer space, but certainly not 'the moon'. However, wire is usually ~black agains t~white background, whereas the wall is grayish on grayish. But if someone were to paint the surrounding Chinese countryside, this might be relevant.

Either way, interstate 80 has much better contrast and I'd guess is upwards of 100 feet wide, so I don't see any way in which the wall would ever be "the only thing that could be seen from space"

JonnyBGood 6 Oct 2005 16:06

Re: The Great Wall of China
 
When I was in las vegas during the summer I was told that the light from the top of the luxar casino can be seen from outer space (where exactly that begins I don't know).

acropolis 6 Oct 2005 16:41

Re: The Great Wall of China
 
Quote:

Originally Posted by JonnyBGood
When I was in las vegas during the summer I was told that the light from the top of the luxar casino can be seen from outer space (where exactly that begins I don't know).

Outer Space is just south of 515 on South Las Vegas. Can't miss it. Great margaritas.

sword 6 Oct 2005 17:25

Re: The Great Wall of China
 
If a gazillion bazillion Ninja's all stood on the Chinese wall and they all had flashing beacons glued to their heads, now that would be something, eh?

Ephor 7 Oct 2005 04:08

Re: The Great Wall of China
 
I feel obliged to thank you all for sharing your wisdom, even if it does leave me disappointed (I should be used to this by now).


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