Alan Guth

The universe is big. We often say that we live in a small world, but the 25,000-mile trek around the planet Earth is still a longer trip than most of us have ever attempted. The farthest location ever reached by humans is the moon, about 240,000 miles from the earth. While the luner landing was a spectacular achievement, we would have to travel 400 times farther if we wished to extend our exploration to the sun. This glowing sphere is so large that if a map of the earth were drawn to cover the sun’s surface, the entire area of our planet would fit comfortably within the outline of the Dominican Republic. The sun is not uniquue, but is one of many stars. A journey to our nearest stellar neighbor, a three -star system called Alpha Centauri, would carry our astronauts a hundred million times faster than a trip to the moon, a distance so great that even light requires four years to traverse it. If the astronauts looked homeward from Alpha Centauri, the separation between the earth and moon would look no bigger than a thumbtack viewed from 400 miles away.