We need, however, a yardstick that makes it possible to compare highly diverse processes, and this yardstick is time. Without time, change has no meaning. And without change, time would stop. Time can be conceived as the intervals during which events occur. Just as money permits us to place a value on both apples and oranges, time permits us to compare unlike processes. When we say that it takes three years to build a dam, we are really saying it takes three times as long as it takes the earth to circle the sun or 31,000,000 times as long as it takes to sharpen a pencil. Time is the currency of exchange that makes it possible to compare the rates at which very different processes play themselves out.

Given the unevenness of change and armed with this yardstick, we still face exhausting difficulties in measuring change. When we speak of the rate of change, we refer to the number of events crowded into an arbitrarily fixed interval of time. Thus we need to define the "events." We need to select our intervals with precision. We need to be careful about the conclusions we draw from the differences we observe. Moreover, in the measurement of change, we are today far more advanced with respect to physical processes than social processes. We know far better, for example, how to measure the rate at which blood flows through the body than the rate at which a rumor flows through society.

Even with all these qualifications, however, there is widespread agreement, reaching from historians and archaeologists all across the spectrum to scientists, sociologists, economists and psychologists, that, many social processes are speeding up – strikingly, even spectacularly.

Painting with the broadest of brush strokes, biologist Julian Huxley informs us that "The tempo of human evolution during recorded history is at least 100,000 times as rapid as that of pre-human evolution." Inventions or improvements of a magnitude that took perhaps 50,000 years to accomplish during the early Paleolithic era were, he says, "run through in a mere millennium toward its close; and with the advent of settled civilization, the unit of change soon became reduced to the century." The rate of change, accelerating throughout the past 5000 years, has become, in his words, "particularly noticeable during the past 300 years."

C. P. Snow, the novelist and scientist, also comments on the new visibility of change. "Until this century ..." he writes, social change was "so slow, that it would pass unnoticed in one person's lifetime. That is no longer so. The rate of change has increased so much that our imagination can't keep up." Indeed, says social psychologist Warren Bennis, the throttle has been pushed so far forward in recent years that "No exaggeration, no hyperbole, no outrage can realistically describe the extent and pace of change.... In fact, only the exaggerations appear to be true."

What changes justify such super-charged language? Let us look at a few – change in the process by which man forms cities, for example. We are now undergoing the most extensive and rapid urbanization the world has ever seen. In 1850 only four cities on the face of the earth had a population of 1,000,000 or more. By 1900 the number had increased to nineteen. But by 1960, there were 141, and today world urban population is rocketing upward at a rate of 6.5 percent per year, according to Edgar de Vries and J. P. Thysse of the Institute of Social Science in The Hague. This single stark statistic means a doubling of the earth's urban population within eleven years.

One way to grasp the meaning of change on so phenomenal a scale is to imagine what would happen if all existing cities, instead of expanding, retained their present size. If this were so, in order to accommodate the new urban millions we would have to build a duplicate city for each of the hundreds that already dot the globe. A new Tokyo, a new Hamburg, a new Rome and Rangoon – and all within eleven years. (This explains why French urban planners are sketching subterranean cities – stores, museums, warehouses and factories to be built under the earth, and why a Japanese architect has blueprinted a city to be built on stilts out over the ocean.)

The same accelerative tendency is instantly apparent in man's consumption of energy. Dr. Homi Bhabha, the late Indian atomic scientist who chaired the first International Conference on the Peaceful Uses of Atomic Energy, once analyzed this trend. "To illustrate," he said, "let us use the letter 'Q' to stand for the energy derived from burning some 33,000 million tons of coal. In the eighteen and one half centuries after Christ, the total energy consumed averaged less than one half Q per century. But by 1850, the rate had risen to one Q per century. Today, the rate is about ten Q per century." This means, roughly speaking, that half of all the energy consumed by man in the past 2,000 years has been consumed in the last one hundred.

Also dramatically evident is the acceleration of economic growth in the nations now racing toward super-industrialism. Despite the fact that they start from a large industrial base, the annual percentage increases in production in these countries are formidable. And the rate of increase is itself increasing.

In France, for example, in the twenty-nine years between 1910 and the outbreak of the second world war, industrial production rose only 5 percent. Yet between 1948 and 1965, in only seventeen years, it increased by roughly 220 percent. Today growth rates of from 5 to 10 percent per year are not uncommon among the most industrialized nations. There are ups and downs, of course. But the direction of change has been unmistakable.

Thus for the twenty-one countries belonging to the Organization for Economic Cooperation and Development – by and large, the "have" nations – the average annual rate of increase in gross national product in the years 1960-1968 ran between 4.5 and 5.0 percent. The United States grew at a rate of 4.5 percent, and Japan led the rest with annual increases averaging 9.8 percent.

What such numbers imply is nothing less revolutionary than a doubling of the total output of goods and services in the advanced societies about every fifteen years – and the doubling times are shrinking. This means, generally speaking, that the child reaching teen age in any of these societies is literally surrounded by twice as much of everything newly manmade as his parents were at the time he was an infant. It means that by the time today's teenager reaches age thirty, perhaps earlier, a second doubling will have occurred. Within a seventy-year lifetime, perhaps five such doublings will take place – meaning, since the increases are compounded, that by the time the individual reaches old age the society around him will be producing thirty-two times as much as when he was born.

Such changes in the ratio between old and new have, as we shall show, an electric impact on the habits, beliefs, and self-image of millions. Never in previous history has this ratio been transformed so radically in so brief a flick of time.

Behind such prodigious economic facts lies that great, growling engine of change – technology. This is not to say that technology is the only source of change in society. Social upheavals can be touched off by a change in the chemical composition of the atmosphere, by alterations in climate, by changes in fertility, and many other factors. Yet technology is indisputably a major force behind the accelerative thrust.

To most people, the term technology conjures up images of smoky steel mills or clanking machines. Perhaps the classic symbol of technology is still the assembly line created by Henry Ford half a century ago and made into a potent social icon by Charlie Chaplin in Modern Times. This symbol, however, has always been inadequate, indeed, misleading, for technology has always been more than factories and machines. The invention of the horse collar in the middle ages led to major changes in agricultural methods and was as much a technological advance as the invention of the Bessemer furnace centuries later. Moreover, technology includes techniques, as well as the machines that may or may not be necessary to apply them. It includes ways to make chemical reactions occur, ways to breed fish, plant forests, light theaters, count votes or teach history.