Cosmos - Carl Sagan [144]
—Ovid, Metamorphoses, first century
In the great cosmic dark there are countless stars and planets both younger and older than our solar system. Although we cannot yet be certain, the same processes that led on Earth to the evolution of life and intelligence should have been operating throughout the Cosmos. There may be a million worlds in the Milky Way Galaxy alone that at this moment are inhabited by beings who are very different from us, and far more advanced. Knowing a great deal is not the same as being smart; intelligence is not information alone but also judgment, the manner in which information is co-ordinated and used. Still, the amount of information to which we have access is one index of our intelligence. The measuring rod, the unit of information, is something called a bit (for binary digit). It is an answer—either yes or no—to an unambiguous question. To specify whether a lamp is on or off requires a single bit of information. To designate one letter out of the twenty-six in the Latin alphabet takes five bits (25 = 2 × 2 × 2 × 2 × 2 = 32, which is more than 26). The verbal information content of this book is a little less than ten million bits, 107. The total number of bits that characterizes an hour-long television program is about 1012. The information in the words and pictures of different books in all the libraries on the Earth is something like 1016 or 1017 bits.* Of course much of it is redundant. Such a number calibrates crudely what humans know. But elsewhere, on older worlds, where life has evolved billions of years earlier than on Earth, perhaps they know 1020 bits or 1030—not just more information but significantly different information.
Of those million worlds inhabited by advanced intelligences, consider a rare planet, the only one in its system with a surface ocean of liquid water. In this rich aquatic environment, many relatively intelligent creatures live—some with eight appendages for grasping; others that communicate among themselves by changing an intricate pattern of bright and dark mottling on their bodies; even clever little creatures from the land who make brief forays into the ocean in vessels of wood or metal. But we seek the dominant intelligences, the grandest creatures on the planet, the sentient and graceful masters of the deep ocean, the great whales.
They are the largest animals† ever to evolve on the planet Earth, larger by far than the dinosaurs. An adult blue whale can be thirty meters long and weigh 150 tons. Many, especially the baleen whales, are placid browsers, straining through vast volumes of ocean for the small animals on which they graze; others eat fish and krill. The whales are recent arrivals in the ocean. Only seventy million years ago their ancestors were carnivorous mammals who migrated in slow steps from the land into the ocean. Among the whales, mothers suckle and care tenderly for their offspring. There is a long childhood in which the adults teach the young. Play is a typical pastime. These are all mammalian characteristics, all important for the development of intelligent beings.
The sea is murky. Sight and smell, which work well for mammals on the land, are not of much use in the depths of the ocean. Those ancestors of the whales who relied on these senses to locate a mate or a baby or a predator did not leave many offspring. So another method was perfected by evolution; it works superbly well and is central to any understanding of the whales: the sense of sound. Some whale sounds are called songs, but we are still ignorant of their true nature and meaning. They range over a broad band of frequencies, down to well below the lowest sound the human ear can detect. A typical whale song lasts for perhaps fifteen minutes; the longest, about