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48 for evidence of oxygen in the atmospheres of planets orbiting nearby stars. Others argue that technological advances make deployment in space a more attractive option for such instruments, although perhaps not for very large radio telescopes.” Dyson proposed in 1963 that we search for gravitational radiation from what he called “gravitational machines” that might be used as interstellar propulsion systems. Two decades later, astronomer John Kraus suggested that gravity waves could be used as a means of communication. The first large gravity wave observatories are now in operation. Lemarchand listed what he called “extravagant methods” for finding evidence of extraterrestrial technological activity. In addition to detecting infrared radiation from a Dyson Sphere, we might discover optical radia- tion from rare isotopes in stellar spectra or observe X-ray pulses from nuclear explosions or from material dropped on to neutron stars. We might look for anomalous gamma-rays generated by matter—antimatter propul- sion systems or artificial neutrino beams. We might discover a coded message capable of replicating matter in suitable environments. Or we might find space probes or other artificial objects in our own solar system. Lemarchand described other methods—wormholes, faster-than-light par- ticles, or the use of physical laws we have not yet discovered—as “exotica” from science fiction.” Mind-Stretcher. “Star Trek’”’’s transporter may not be totally fanciful. William Reupke of the Computer Sciences Corporation thought it might be possible to transmit enough information over interstellar distances to recreate physical objects—including human beings. Matter transmitters deployed elsewhere in the Galaxy could provide new targets in the search for extraterrestrial intelligence.” We do not know which of these techniques, if any, will reveal the pres- ence of alien minds. What we are looking for, Shostak reminded us, is an uncertain manifestation of a hypothetical presence.”! SETI researchers continue to push back the horizon of possibility, with admirable dedication. Their enthusiasm is contagious, although their underlying beliefs are not yet proven. Searching for Intelligence Exotic Means