For more than 50 years, the usual answer has been \u2018among the stars\u2019, with the search for extraterrestrial intelligence<\/a> (SETI) focused on scanning the skies with large radio telescopes.<\/p>\n That might be changing, as a new generation of SETI experiments and scientists join the hunt.<\/p>\n Some want to look for alien artefacts in the Solar System, a plan sure to appeal to anyone who remembers 2001: A Space Odyssey<\/i><\/span>\u2019s sinister black monolith.<\/p>\n The trouble is that there is a lot of Solar System to investigate, and so it helps in your search if you have some idea of what the aliens might be up to.<\/p>\n For more on SETI and UFOs, read our guides on the <\/strong><\/em>Roswell Incident<\/strong><\/a> and things <\/a><\/em>commonly mistaken for UFOs<\/a>.<\/strong><\/em><\/p>\n The authors of one paper on the subject start with the idea that any alien probes exploring our neighbourhood would need to report back to their home system.<\/p>\n Doing that, though, is hard, requiring what is presumably a modest probe to use an enormous amount of power to send a detectable signal over interstellar distances.<\/p>\n Any sensible alien spacecraft engineers would look for a shortcut.<\/p>\n Luckily, they should know that radio waves, like any electromagnetic<\/a> radiation, can be lensed and magnified by the Sun\u2019s gravity.<\/p>\n Position a probe about 500 times the Earth\u2013Sun distance behind the Sun, exactly in line with your home star, and it should be possible to get a report on Earth\u2019s status back home with transmitters not much more powerful than those our own spacecraft carry today.<\/p>\n If we pay attention when Earth crosses the region between the Sun and a target star, looking for any stray signals with radio telescopes, we might be able to eavesdrop on their communications.<\/p>\n This paper, the result of a summer project for some lucky undergraduates at Penn State University\u2019s SETI centre, used the Green Bank Telescope in radio-quiet West Virginia to do just that.<\/p>\n As ever with a SETI project, the biggest problem is distinguishing what might be an artificial transmission from all the noise and clutter generated by our terrestrial civilisation.<\/p>\n In this case, we expect the source of a real signal to be close to stationary relative to the Sun, so we can pay attention only to those signals.<\/p>\n A few candidate events are found in both the frequency bands that the astronomers targeted, but close inspection shows them to be false alarms.<\/p>\n The brightest in a range of frequencies known as the L band, for example, seems to be chatter from an Iridium communications satellite.<\/p>\n Despite this non-detection, the technique has promise. After all, it\u2019s only one set of observations.<\/p>\n Perhaps our beacon reports to the Alpha Centaurians only once a week, or once a year. Or perhaps Alpha Centauri<\/a> is the wrong target.<\/p>\n Could the Zeta Reticuli<\/a> system be the place to look, if many UFO theories are to be believed?<\/span><\/p>\n It\u2019s possible, the authors say, to imagine an interstellar communications network, with relay satellites positioned throughout the Galaxy to forward messages via gravitational lensing<\/a>.<\/p>\n In such a system, multiple star systems like Alpha Centauri, with its two bright components plus faint Proxima, are poor choices, forcing their beacons to adjust position constantly as the stars move.<\/p>\n Much better to look for signals pinging between nodes anchored on more boring stars \u2013 just like our Sun. We should probably keep looking.<\/p>\n![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2022\/08\/GettyImages-89436585-fae3692-e1660817015466.jpg?quality=90&resize=620%2C413"\" "\\"\"\"\\"\/")
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<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>How to find a genuine extra terrestrial signal<\/strong><\/h2>\n
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