For a long time, people have been seeing strange objects in the sky. These unexplained flying objects, or UFOs, are often called flying saucers. In 1917 a Pennsylvania teenager claimed to have seen a saucer-shaped object with rows of lights. In 1947, bits of what may have been a crashed UFO were found near Roswell, New Mexico. In 1952, UFOs played tag with fighter pilots in the skies over the Capitol Building in Washington, D.C. Are UFOs spaceships from another planet? Or are they really just unusual cloud formations, weather balloons or top-secret military aircrafts?