Can we really see the Great Wall of China from moon?

                              We are aware of the 'fact' that -- The Great Wall of China is the only human-made object that can be seen from outer-space. Is this really true?

                               Let us think about this - If the great wall of China is visible from outer space and moon, every national highway of India and state highways of many countries which stretch for thousands of miles would have been visible too.

                              The fact was published in 1938 when no one traveled in space. Since then, many astronauts who worked on Skylab, who orbited the earth etc looked at earth and haven't found the Great Wall visible to them.

                              The Great Wall is about 20 feet (about 6 metres) in width., 5500 miles long. This is not a big target to see from the Moon which is  384,400 kms away. In order to be visible from far away, it would also have to be very wide and distinct looking from the ground. The Great Wall is very thin.

So, what is visible from outer space?

                              Well, with our naked eye nothing is visible. Many things can be seen using powerful instruments. However, there is an exception here. We can see the pyramids of Giza. It is covered with highly polished limestone. These stones reflected the sun light and made the pyramid shine like a jewel. The original pyramid with its casing stones would act like a very big mirror and reflect light so powerful that it would be visible from the moon as a shining star on earth.