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44 If there are beings with radio out there, if they are willing to transmit mes- sages into the unresponsive void (instead of just listening as we are), and if we listen in the right direction at the right time and the right frequency with the right bandwidth and the right detection scheme, then the radio approach to SETI will make a significant contribution to our knowledge. —Physicist Robert L. Forward, 1994** For more than 40 years, the attraction of searching in the radio sector of the electromagnetic spectrum has been compelling. As Drake saw it, radio has two enormous advantages for interstellar communication: The galaxy is transparent to radio waves, and radio does not need to be aimed accurately. Radio also is more economical; it is cheaper to send radio photons than visible-light photons.” Early observing programs adapted radio astronomy equipment to SETI tasks. Shklovskii offered a pragmatic reason for choosing radio frequen- cies: No one could accuse searchers of wasting money, as the equipment could be used for conventional radio astronomy.” Whatever its advantages may be, searching by radio is not a comprehen- sive approach; we may be limiting our attention to a very restricted subset of all technological civilizations. By 1979, even Drake was worrying that the choice of radio had been unduly influenced by our booming expertise in radio technology. As early as 1961, laser pioneers Charles Townes and Robert Schwartz proposed that we use masers—including lasers—for interstellar communi- cations. It may have been an historical accident that lasers were not dis- covered before radio as a means of long-range communication.” Optical beacons now are almost as easy to detect as radio beacons. We could see a powerful pulsed laser a few dozen light-years away; a tightly focused laser beam could greatly outshine a planet’s host star at a particu- lar wavelength.* Some astronomers already have conducted limited searches for laser signals. Stuart Kingsley, who pioneered these efforts in 1990, has argued that only lasers have the ability to probe interstellar space free of the sig- nificant distortion that smears radio signals. However, there is a disadvan- tage. Although optical SETI does not face terrestrial interference, it does require that the extraterrestrials deliberately target us with their lasers.“ The Planetary Society initiated a new search for laser signals in 2006, using a telescope in Massachusetts. There have been more exotic proposals for optical detection. Morrison raised the possibility of interstellar communication by modulating the visible light of a star. Extraterrestrials might attract attention by placing large objects in star-hugging orbits, proposed Luc Arnold of France’s Haute-Provence Observatory; from the perspective of other civilizations, Searching for Intelligence Other Wavelengths, Other Technologies