What does the Great Wall of China look like from space? Can you really see it? -- Janna L., 14, from Clarke High School in Clarke, Arkansa

Contrary to popular belief, the Great Wall of China cannot be seen from space. In fact, no man-made object is visible with the naked eye from space. At a low orbit, such as that of a space shuttle, large man-made features, such as highways, bridges and the Great Wall can barely be seen. All that is visible once you leave the earth's orbit and gain a few thousand miles of altitude are geographic features.