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The Wall of China from the moon?

We've all heard the phrase "the only human construction visible to the naked eye from the moon is the Great Wall of China."

Richard Halliburton, who created the phrase.

has been repeated so often that it has even been published in school books. There is a version more "soft" only said that viewed from the orbit of a spacecraft ....

History

Many think any astronaut said when he went to the moon, but the most accepted version is that it said the writer of adventure (and adventurous) Richard Halliburton.

I wrote in the early 30 ', in the book " Books of marvels, the Orient " long before the man on the moon. This managed to appear in the book of oddities of Ripley, which then was considered as a truth for long.

the end it's true or not? Let

a little more deeply into the situation, from the scientific point of view.

To solve this we know:

1. What is the maximum resolution of the eye
2. The value represents the Moon.
What are
3. the measurements of the Great Wall of China.

1) The Resolution of the eye:

This value is well known for a long time.

The eye can define ('solve' in terminology of telescopes) a minute of arc (if you got good eyesight!).

2) The accounts

The Moon has an average of 30 minutes of arc, and its real diameter is about 3500 km. With the data of point 1) and a simple rule of thumb, we can calculate that 1 minute of arc is 117 km from the moon.

Although the Moon has an elliptical orbit, which sometimes is closer to the maximum definition of the eye to the distance Earth - Moon is about 100 km.

3) Measures for the Wall

La Muralla measures more than 2400 km, and at no time does not exceed 30 meters wide.

are lots of photos of the Great Wall, but I found it very curious, and who have used it as a gateway ....

Conclusion:

Not too hard to answer:

NOT see the Great Wall of China to the naked eye from the moon.

Certainly
currently no human construction is, unless some artificial lake created by a dam, or loss of the forest for the trees cut down fierce, but a "selenite" does not have to assume that these changes are artificial. And

telescope?

bear the thought even further:

With telescope see? What's more: We will be spying from the moon?

The best resolution is achieved with a telescope is 0.3 arcsec (0.3 ") approximately, and is due to seeing .

Although the moon has no atmosphere, the Earth itself so the effect is the same.

Even when conditions are exceptional and can reach 0.1 "implies a definition of 200 meters ...

With a telescope, several meters in diameter and current technology, under certain lighting conditions (dusk or dawn to cast a longer shadow ) and atmospheric stability in the area of \u200b\u200bthe wall, it would start just a glimpse ...

This reasoning applies also to the Moon from Earth: the best pictures you can get from the Moon have a resolution of about 200 meters.

This image shows the maximum that can be done on the Moon from Earth. The French took three amateurs, P. Tosi, E. Rouseet and J. Luc Dauvergne, with a 1-meter telescope from Pic du Midi. The smallest details are less than 300 meters. It is the Alpine Valley region.

To get to see the Wall from the moon as seen in the photo below, which has a definition of 1 meter (0.0005 represents!) Would require a telescope 230 meters in diameter! !

picture from a plane of the Great Wall, at 7000 meters. It has a definition of 1 meter.

As we can see from the ground up details 200 meters, we can rest assured that there can be no selenite taking us out photos with this definition, because we would have seen his telescope 230 meters in diameter! (*)

be seen from the orbit of a satellite?

We stayed pending the issue if viewed from the orbit of a spacecraft.

best thing is the comment of a shuttle astronaut Jay Apt: We

the Great Wall of China. Auque saw small buildings, such as runways, the Great Wall is made of materials with color that is indistinguishable from the surrounding terrain. Despite persistent stories that can be seen from the moon, for us it was invisible from only 180 miles!

(*) This is one I take poetic license. The ever seeing let them see with this definition.