Yuri's Planet 

From the first time I laid my eyes on it, I was astounded by the picture above. On April 12th, 1961, Yuri Alexseyevich Gagarin saw Earth from outer space. Yuri was the first human to see the planet from an outer space view and described it as rather dark and blue, but clear nonetheless. Yuri's description of our planet is greatly contrasted by the above photograph, taken much more recently. The photograph depicts a present day Earth, illuminated by lights that vividly show the locations of various cities, such as New York City, Philadelphia, Baltimore, etc. Although the International Space Station is orbiting close to Earth, it still amazes me that it was able to capture an image of the world in such a vivacious way. I, myself, was shocked to see that so many lights could be seen from outer space. This is the main reason that I selected this photograph—I used to believe that no lights could be seen from outer space due to the great distance from the ground level, but now I recognize that as a great misconception. While I am still awed and in shock from this photograph, many questions are rapidly forming in my mind. For example, how far away would you have to get from Earth for these radiant lights to appear extinguished? Also, how much power or energy is used on Earth for an image such as this one to be able to be captured from outer space?

Source:  http://apod.nasa.gov/apod/ap130412.html