With a crackling sound like that of frying eggs, an undulating thread of intense, blue-white light dances across the small space between the tips of two metal rods. Using his spark-gap transmitter, a mild-mannered 31-year-old physics professor demonstrates electromagnetic phenomena to students in a dimly lit classroom at the University of Karlsruhe in Germany. The year is 1887, and Heinrich Hertz is generating radio waves. Seven years later a young Italian named Guglielmo Marconi reads a journal article by Hertz while vacationing in the Alps and abruptly rushes home with a vision of a wireless telegraph in his head. Soon Marconi's own spark-gap transmitters are sending Morse-code pulse streams across his lab without wires. After boosting power and building much larger antennas, the radio pioneer eventually uses the device to transmit coded wireless signals across the Atlantic Ocean in 1901.

Fast-forward a century, and researchers are once again beaming short electromagnetic pulses across their labs. But the technology has changed. Hertz's and Marconi's bulky coils and capacitors have been replaced by tiny integrated circuits and tunnel diodes. Likewise, the ragged and erratic spark streams emitted by early transmitters have now been refined into precisely timed sequences of specially shaped pulses lasting only a few hundred trillionths of a second each. And whereas Marconi's devices could convey the equivalent of about 10 bits of data per second, today's short-range, low-power descendant of the original spark-gap systems--called ultrawideband (UWB) wireless technology--can send more than 100 million bits of digital information in the same amount of time.

   
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