With a simple snap of our fingers, each of us taps vast sources of energy hundreds of times per day thanks to coal, oil, wind, water, the hidden power of the atom, and the radiant power of the sun itself - all of which are converted into electricity, the modern world's workhorse.

In a newspaper interview in 1895, Thomas Edison forecast the future of transportation with no attempt to hedge his bets. America's most famous inventor remarked, "The horseless vehicle is the next great miracle." "It will only be a matter of time before all carriages and trucks in the major cities are powered by engines." The actual nature of the engines was to remain a mystery for many years.

When the twentieth century began, no human being had yet flown a motorized airplane. By the turn of the century, millions were flying, and some were even flying through space. The first powered flight with a pilot lasted 12 seconds and carried a person 120 feet. Today, hundreds of passengers are carried halfway around the world on nonstop commercial flights that last up to 15 hours.

Water was in high demand with short supply in the United States and many other countries around the turn of the century. As the country's population grew, cities across the country yearned for more water, and much of the West saw it as the missing element for growth and progress. Simultaneously, existing water systems were in disrepair and posed a direct threat to public health.

The new electrical breakthrough drew a yawn when it was introduced to the public in mid-1948. "A gadget known as a transistor, which has a number of uses in the radio industry where a vacuum tube is generally utilized, was introduced for the first time yesterday at Bell Telephone Laboratories," an unimpressed writer for The New York Times stated on page 46 of the daily edition.

In the fall of 1899, a novel means of communication made its way into the coverage of an important sporting event. Off the coast of New York Harbor, two sleek sailboats-the Columbia of the New York Yacht Club and the Shamrock of Ulster Yacht Club Ireland-were battling for the coveted America's Cup. Until now, the public had been oblivious to events on the water until spectators returned to shore after the races. This time, however, reports "rushed through the air with the simplicity of light," as one breathless newspaper reporter described it.

Large, perfect circles in various shades of green, gold, or brown, stretching to the horizon in a massive checkerboard pattern, are frequently observed via the window of a long-distance airliner. These genuine crop circles are a sure proof of an automatic irrigation system - and a sign of a revolution in agriculture, the oldest of all human pursuits - in most of the American Midwest and on farms all over the world. This transformation is driven by a single concept: mechanization.

The computer depicted on the cover of Popular Electronics magazine's January 1975 issue seemed impressive - "World's First Minicomputer Kit to Rival Commercial Models" - and for $397 for the parts, it seemed like a wonderful steal. Toggle switches were used for programming, the memory stored just 256 bytes of data, and the output was in the form of blink patterns. We've come a long way. 

"The telephone," Alexander Graham Bell said in a prospectus asking funding for his new invention in 1877, "may be concisely characterized as an electrical apparatus for reproducing the tones and articulations of a speaker's voice at distant places. It is conceivable that cables of telephone wires might be laid underground or suspended overhead and connected by branch wires with private dwellings, country houses, shops, manufactories, and so on." His vision became reality. 

Which of your household's appliances would you find the most difficult to live without? A recent survey found that the refrigerator was the most commonly used answer. Over the course of the past century, this once-luxurious item became an essential element of the American household, appearing in more than 99.5 percent of the country's family kitchens by the end of the century.

William Durant, the creator of General Motors, was known for his far-reaching ideals, and he continued in that vein in a 1922 interview. "Most of us will live to see the entire country covered with a network of roadways created from point to point as the bird flies, as the hills are cleared, valleys crossed, and barriers removed," he remarked. Given the depth of America's obsession with automobiles, his prognosis wasn't so far-fetched.

On October 4, 1957, the Soviet Union launched the first spacecraft, a 184-pound satellite dubbed Sputnik, from the plains of Kazakhstan. Despite its historic significance, the event was so cloaked in mystery that no images were taken. But no one who was there, or who heard about it, will ever forget the experience. 

The conference, held in October 1972 on the website of the Washington Hilton, was not intended to launch a revolution. It was held for a technological elite and served to introduce ARPANET, a new type of network established under military supervision to let computer scientists communicate knowledge and harness the processing power of faraway machines. However, traffic on the system was still low, and many potential users thought it was too complicated to have much of a future.

To see with a sharper eye has been a human fascination since the era of Leeuwenhoek and Galileo, the fathers of the microscope and telescope, respectively. Sharper vision means being able to see what was far away or extremely small more clearly - enlarged and sharpened - for centuries. However, in the twentieth century, the phrase began to be used for all kinds of seeing that were originally thought to be "magical" - breaking veils around and inside us, and recognizing "light forms" to which the human eye is absolutely blind.

In 1930, Good Housekeeping magazine, which commonly promoted domestic fantasies, stated rhetorically, "How many times have you hoped you could push a button and find your meals deliciously prepared and delivered, and then just as simply put away with the push of a button?" There was, of course, no such button or switch in sight - not for cooking meals, cleaning the house, doing laundry, or any of the other household activities that, according to ancient custom, were primarily performed by women.

In 1900, the average life expectancy was 47 years. In 2000, it was 77. This huge increase was the result of several primary factors, including the establishment of a reliable water supply. However, most of the credit deserves to go to the numerous medical advances in diagnostics, medications, and medical devices.

If coal reigned supreme in the nineteenth century, petroleum reigned supreme in the twentieth. Refined petroleum, also known as "rock oil," literally became the fuel of the twentieth century, powering automobiles, airplanes, farm implements, and industrial machines.

The possibilities of a breakthrough in telecommunications increased dramatically in the mid-twentieth century. Most long-distance communication was carried by copper or coaxial cable at the time, but electricity was limited and expensive, and demand far outstripped supply. However, during the next few decades, the telephone singlehandedly erased bottlenecks in long-distance communications.

Proponents of nuclear technology have long portrayed efforts to develop peaceful applications of atomic energy as "turning swords into plowshares." In an ongoing debate, opponents object to the destructive potential of the technology, claiming that, despite its benefits, it is nearly always a hazardous tool. However, behind the disagreement is a history of scientific and technical discoveries that have occurred in a relatively short period of time - with extraordinary impact on the globe, both for better and for worse.

"All hail, King Steel," Carnegie said, honoring the metal's monarch for creating "wonders on earth." Carnegie and other industrial giants were now producing millions of tons of steel per year, used for the supporting framework of bridges and skyscrapers, the tracks of vast railroad networks, the frames and plates of steamboat hulls, and a host of other applications from food cans to road signs.