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187 If aliens are in our solar system, they may avoid Earth for some reason such as biological incompatibility, excessive gravity, or an ethic of noninterference. Other parts of our solar system may be of greater interest os oe to them. We have detected an alien presence in our solar system, but we do not recognize it or do not consider the evidence persuasive. More advanced civilizations may not need planets or stars. They may be scattered through interstellar space, but not in our solar system. More advanced civilizations may find searching and communicating by signals more useful than sending probes, inhabited vehicles, or other artifacts. Their science and technology make interstellar exploration or expansion irrelevant. They may have evolved to a stage where interstellar vehicles are ants No civilization has ever engaged in astroengineering. It may seem infeasi- ble or not worth the cost. No civilization has engaged in astroengineering activities that we can detect with our present technologies or search strategies. We have detected evidence of astroengineering but do not recognize ie it. Many have disputed the very existence of a paradox. The absence of visi- tors in our solar system has little meaning, Newman declared, because it depends on a series of questionable assumptions: If extraterrestrial life is abundant, if space travel is relatively easy, if advanced civilizations feel compelled to explore the galaxy and can do so, if they have had enough Is There a Paradox? Here and Misunderstood Who Needs Planets? They Are Not Travelers Beyond Our Imaginations not necessary. A Subcase: Astroengineering Is There a Paradox?