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phonetic writing so we could put our sounds down on paper and, by glancing at a page, hear someone speaking in our head—an invention that became so widespread in the last few thousand years that we hardly ever stop to consider how astonishing it is.
    Speech is not really communicated instantaneously: When we make a sound, we are creating traveling waves in the air carried at the speed of sound. For practical purposes that’s nearly instantaneous. But the trouble is that your shout carries only so far. It’s a very rare person who can carry on a coherent conversation with someone even 100 meters away.
    Until comparatively recently human population densities were very low. There was hardly any reason to communicate with someone more than 100 meters away. Almost no one—except members of our itinerant family group—ever came close enough to communicate with us. On the rare occasions that someone did, we were generally hostile. Ethnocentrism—the idea that our little group, no matter which one it is, is better than any other—and xenophobia—a “shoot first, ask questions later” fear of strangers—are deeply built into us. They are by no means peculiarly human; all our monkey and ape cousins behave similarly, as do many other mammals. These attitudes are at least aided and abetted by the short distances over which speech is possible.
    If we’re isolated for long periods from those other guys, we and they slowly develop in different directions. Their warriors start wearing ocelot skins, for example, instead of eagle feather headdresses—which everybody around here knows are fashionable, proper, and sane. Their language eventually becomes different from ours, their gods have strange names and demand bizarre ceremonies and sacrifices. Isolation breeds diversity; and our small numbers and limited communications range guarantee isolation. The human family—originating in one small locale in East Africa a few million years ago—wandered, separated, diversified, and became strangers to one another.
    The reversal of this trend—the movement toward the reacquaintance and reunification of the lost tribes of the human family, the binding up of the species—has occurred only fairly recently and only because of advances in technology. The domestication of the horse permitted us to send messages (and ourselves) over distances of hundreds of miles in a few days. Advances in sailing ship technology allowed us to travel to the most distant reaches of the planet—but slowly: In the eighteenth century, it took about two years to sail from Europe to China. By this time, far-flung human communities could send ambassadors to each other’s courts, and exchange products of economic importance. However, for the great majority of eighteenth-century Chinese, Europeans could not have been more exotic had they lived on the Moon, and vice versa. The real binding up and deprovincialization of the planet requires a technology that communicates much faster than horse or sailing ship, that conveys information all over the world, and that is cheap enough to be available, at least occasionally, to the average person. Such a technology began with the invention of the telegraph and the laying of submarine cables; was greatly expanded by the invention of the telephone, using the same cables; and then enormously proliferatedwith the invention of radio, television, and satellite communications technology.
    Today we communicate—routinely, casually, with hardly ever a second thought—at the speed of light. From the speed of horse or sailing ship to the speed of light is an improvement by a factor of almost a hundred million. For fundamental reasons at the heart of the way the world works, codified in Einstein’s special theory of relativity, we know that there is no way we can send information faster than light. In a century, we have reached the ultimate speed limit. The technology is so powerful, its implications so far-reaching, that of course