As Voyager 1 left our planetary neighbourhood for the fringes of the solar system on February 14, 1990, engineers turned it around, at Carl Sagan's suggestion, for one last look at its home planet. Voyager 1 was about 6.4 billion kilometers (4 billion miles) away, and approximately 32 degrees above the ecliptic plane, when it captured this portrait of our world. Caught in the center of scattered light rays (a result of taking the picture so close to the Sun), Earth appears as a tiny point of light,...