Charles (Charlie) Townes, a physicist who won the Nobel Prize in 1964 for his invention of the maser – the radio equivalent of a laser – has died at the age of 99.

Townes was an important figure in the SETI community.  In the 1990s, he changed the mindset of researchers who were conducting experiments to look for signals that were generated by intelligent beings on other worlds.  Their approach had been to employ large antennas to hunt for radio transmissions.  An alternative scheme to use mirror and lens telescopes to look for flashing lights (optical SETI) was considered far less attractive.  The reason for this lack of enthusiasm was the fact that light photons are 500 thousand times more energetic than a microwave radio photon.  It was presumed that the extraterrestrials, mindful of the energy cost in sending signals across cosmic distances, would much prefer radio to optical.  But Townes pointed out that lasers, unlike radio transmitters, could – when used with some inexpensive optics – be easily focused into very narrow beams.  This mitigated the cost differential between sending radio and optical messages, at least if the extraterrestrials are deliberately targeting a specific star system.

For his insights into how scientists might search for intelligence in the cosmos, as well as his service as a member of the SETI Institute’s Board of Trustees, Charlie Townes became the second person to be awarded the Frank Drake Award, which was presented to him in 2002.

Townes, who was at the University of California at Berkeley for much of his career, was an exceptional scientist.  A product of a rural upbringing, he was approachable and soft spoken.  He had the gift of genius, but he would be the last to say that.