Pale Blue Dot - Carl Sagan [5]
The plan of the book is roughly this: We first examine the widespread claims made over all of human history that our world and our species are unique, and even central to the workings and purpose of the Cosmos. We venture through the Solar System in the footsteps of the latest voyages of exploration and discovery, and then assess the reasons commonly offered for sending humans into space. In the last and most speculative part of the book, I trace how I imagine that our long-term future in space will work itself out.
Pale Blue Dot is about a new recognition, still slowly overtaking us, of our coordinates, our place in the Universe—and how, even if the call of the open road is muted in our time, a central element of the human future lies far beyond the Earth.
*“As to the fable that there are Antipodes,” wrote St. Augustine in the fifth century, “that is to say, men on the opposite side of the earth, where the sun rises when it sets to us, men who walk with their feet opposite ours, that is on no ground credible.” Even if some unknown landmass is there, and not just ocean, “there was only one pair of original ancestors, and it is inconceivable that such distant regions should have been peopled by Adam’s descendants.”
CHAPTER 1
YOU ARE HERE
The entire Earth is but a point, and the place of our own habitation but a minute corner of it.
—MARCUS AURELIUS, ROMAN EMPEROR,
MEDITATIONS, BOOK 4 (CA. 170)
As the astronomers unanimously teach, the circuit of the whole earth, which to us seems endless, compared with the greatness of the universe has the likeness of a mere tiny point.
—AMMIANUS MARCELLINUS (CA. 330–395),
THE LAST MAJOR ROMAN HISTORIAN,
IN THE CHRONICLE OF EVENTS
The spacecraft was a long way from home, beyond the orbit of the outermost planet and high above the ecliptic plane—which is an imaginary flat surface that we can think of as something like a racetrack in which the orbits of the planets are mainly confined. The ship was speeding away from the Sun at 40,000 miles per hour. But in early February of 1990, it was overtaken by an urgent message from Earth.
Obediently, it turned its cameras back toward the now-distant planets. Slewing its scan platform from one spot in the sky to another, it snapped 60 pictures and stored them in digital form on its tape recorder. Then, slowly, in March, April, and May, it radioed the data back to Earth. Each image was composed of 640,000 individual picture elements (“pixels”), like the dots in a newspaper wirephoto or a pointillist painting. The spacecraft was 3.7 billion miles away from Earth, so far away that it took each pixel 5½ hours, traveling at the speed of light, to reach us. The pictures might have been returned earlier, but the big radio telescopes in California, Spain, and Australia that receive these whispers from the edge of the Solar System had responsibilities to other ships that ply the sea of space—among them, Magellan, bound for Venus, and Galileo on its tortuous passage to Jupiter.
Voyager 1 was so high above the ecliptic plane because, in 1981, it had made a close pass by Titan, the giant moon of Saturn. Its sister ship, Voyager 2, was dispatched on a different trajectory, within the ecliptic plane, and so she was able to perform her celebrated explorations of Uranus and Neptune. The two Voyager robots have explored four planets and nearly sixty moons. They are triumphs of human engineering and one of the glories of the American space program. They will be in the history books when much else about our time is forgotten.
The Voyagers were guaranteed to work only until the Saturn encounter. I thought it might be a good idea, just after Saturn, to have them take one last glance homeward. From Saturn, I knew, the Earth would appear too small for Voyager to make out any detail. Our planet would be just a point of light, a lonely pixel, hardly distinguishable from the many other points of light Voyager could see, nearby