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45 those objects would transit the stars and produce light curves whose arti- ficial nature would be recognizable. Astronomer Martin Harwit suggested that other civilizations might transmit information by twisting light rather than using other encoding methods.* The radio compulsion is yielding to a more eclectic view as SETI becomes multispectral. The authors of the SETI 2020 report recommended broad- ening the frequency range of searches to include optical and infrared wavelengths, looking for both continuous wave and pulsed signals. Detect- ing optical pulses may be limited to a few thousand light-years, but infrared pulses may be detected all the way to the galactic center. The “holy grail” of an all-sky, all-frequencies, all the time search can be discerned on the horizon of radio technology, according to this group of experts. Its optical counterpart cannot be far behind.*° Thanks to rocket technology that has enabled us to place robotic observa- tories in orbit, astronomers now can study much wider ranges of the elec- tromagnetic spectrum. In addition to the U.S—Europe Hubble Space Telescope, NASA and other space agencies have deployed major instru- ments observing in the infrared, X-ray, and gamma-ray regions of the spectrum. Although none are designed to search for extraterrestrial tech- nology, their findings may have significant implications for SETI. Experts have concluded that all wavebands—radio/microwave, infrared/ optical, X-ray/gamma-ray—are worthy of consideration for SETI searches. As X-ray and gamma-ray observations must take place above the atmo- sphere, searches undertaken just for SETI will remain too costly in the near future.” Bursts of Energy Gamma-ray bursts (GRBs), which may be caused by the collapse of massive stars or the merger of neutron stars, are among the most power- ful energy sources in the cosmos. The rays from the brightest events are so highly collimated that they can be seen across the observable universe. Because bursters concentrate their energy in beams, we only see the one in every several hundred of them that is pointed in our direction. The true rate of GRBs is much higher than it appears.** That also could be true of brief, targeted communications between advanced societies, or among the scattered worlds of a star-faring civi- lization. Only rarely would the Earth pass through a communications beam. If we detect one, there may be many more. Above the Clouds Above the Clouds