1951: The first thermonuclear device is detonated by the United States in the mid-Pacific. The island atoll of Eniwetok is obliterated by the blast. Few precautions are taken to protect nearby inhabitants from radiation poisoning.

1997: A significant percentage of the United State's electricity is generated by nuclear power plants, despite several near meltdowns in the last few decades, including mishaps at Three Mile Island, Pennsylvania, and Monroe, Michigan.

1951: The world's first commercial computer, the Univac, is produced by Remington Rand. The machine fills an entire room and requires several experts to run it.

1997: The Pentium chip manufactured by the Intel Corporation is installed in 90 percent of all new personal computers. A common microprocessor chip is about the size of a fingernail.

1951: Bell Telephone initiates the first long-distance direct telephone dialing.

1997: Communications corporations forge an agreement with the government to develop digital, high-definition television signals for...