One of the most spectacular -- and controversial -- accomplishments of U.S. technology has been the harnessing of nuclear energy. The concepts that led to the splitting of the atom were developed by the scientists of many countries, but the conversion of these ideas into the reality of nuclear fission was the achievement of U.S. scientists in the early 1940s.

 

After German physicists split a uranium nucleus in 1938, Albert Einstein, Enrico Fermi, and Leo Szilard concluded that a nuclear chain reaction was feasible. In a letter to President Franklin Roosevelt, Einstein warned that this breakthrough would permit the construction of "extremely powerful bombs." His warning inspired the Manhattan Project, the U.S. effort to be the first to build an atomic bomb. The project bore fruit when the first such bomb was exploded in New Mexico on July 16, 1945.

 

The development of the bomb and its use against Japan in August of 1945 initiated the Atomic Age, a time of anxiety over weapons of mass destruction that has lasted through the Cold War and down to the antiproliferation efforts of today. But the Atomic Age has also been characterized by peaceful uses of atomic energy, as in nuclear power and nuclear medicine.

 

The first U.S. commercial nuclear power plant started operation in Illinois in 1956. At the time, the future for nuclear energy in the United States looked bright. But opponents criticized the safety of power plants and questioned whether safe disposal of nuclear waste could be assured. A 1979 accident at Three Mile Island in Pennsylvania turned many Americans against nuclear power. The cost of building a nuclear power plant escalated, and other, more economical sources of power began to look more appealing. During the 1970s and 1980s, plans for several nuclear plants were cancelled, and the future of nuclear power remains in a state of uncertainty in the United States.

 

Meanwhile, American scientists have been experimenting with other renewable sources of energy, including solar power. Although solar power generation is still not economical in much of the United States, recent developments might make it more affordable.

 

In 1994 Subhendu Guha, executive vice president of United Solar Systems in Troy, Michigan, was lecturing on the benefits of solar energy and showing a picture of solar cells arrayed on the roof of a house. An architect in the audience said, "But it's so ugly. Who would want that on their house?" That remark got Guha thinking about how to make the photovoltaics look more like the roof, instead of mounting the solar cells on frames that jut skyward.

 

Two years later, Guha's innovation came off the assembly line -- solar shingles that can be nailed directly onto the roof. The shingles are made from stainless steel sheeting, coated with nine layers of silicon, a semiconducting film, and protective plastic. Roofers install the shingles just as they do normal ones, but they must drill a hole in the roof for electrical leads from each shingle. Guha believes that his shingles will be economical in some parts of the United States as their energy efficiency improves and their production cost decreases. Meanwhile, they are already being used in Egypt, Mexico, and other developing countries. In 2002, United Solar Systems increased its production capacity by installing the largest known photovoltaic solar-cell manufacturing machine at its Michigan plant.

 

Another application of solar power is being tested at the U.S. Department of Energy's National Solar Thermal Test Facility in Albuquerque, New Mexico. Scientists have paired parabolic dishes to collect sunlight with engines that automatically operate the system in remote locations. The primary applications of the Advanced Dish Development System (ADDS) are water pumping and village electrification. The system shows promise for parts of the southwest United States and for developing countries.