Visitors from space may have landed on our planet dozens, even hundreds of times during the long, empty ages while Man was still a dream of the distant future. Indeed, they could have landed on 90 percent of the earth as recently as two or three hundred years ago, and we could never have heard of it. If one searches through old newspapers and local records, one can find many reports of strange incidents that could be interpreted as visits from outer space. A stimulating writer, Charles Fort, has made a collection of UFO sighting in his book! One is tempted to believe them more than any modern reports, for the simple reason that they happened long before anyone had ever thought of space travel. Yet at the same time, one can't take them too seriously, for before scientific education was widespread, even sightings of meteors, comets, auroras, and so on, gave rise to the most incredible stories, as they still do today. According to the passage, visitors from space may have landed on the earth ______.