World Atlas [antikvár]

THE UNIVERSE Eortli in Perspective Where are we? If you are asked that question, you answer with the name of your street, your town, perhaps your country. But what if that question were put to you by a visitor from outer space who suddenly found himself at your doorstep? "You are on the Earth," would be your answer. "Earth," he responds. "Where is Earth?" Few people on this planet could begin to give a meaningful answer to that question. Hopefully, this presentation of the universe will give you that answer and with it a better understanding of where we are among the billions of stars and the almost Incomprehensible distance and darkness that surround us. The Earth is one of a group of planets and other bodies that sweep around a medium-sized star called the Sun. The Sun, in turn, is part of a galaxy, the Milky Way, contain- ing billions of stars, many of which probably have satellites, planets similar to the Earth. Pulsing within the galaxy are double stars, dying stars, giant stars, and mysterious stars. And beyond the Milky Way are other galaxies of which we are only faintly aware with our most sensitive scientific sensing devices. A three dimensional map of this vastness—in which the distance between two nearby stars can only be measured In the number of hundreds of years it takes a beam of light to reach from one to the other—is being put together slowly by Earth's astronomers and may never be completed. But with advanced scientific equipment and the first tentative realities of space flight, we are beginning to understand where we are if not why.