Remote communication is not new. Before the appearance of mobiles and e-mails, the telegraph and morse code, the Amerindians transmitted messages by smoke signals and many African people did so by making different sounds on the drums. But how do you get the attention of potential populations millions of miles away? With lasers. This is, at least, what researchers at the Massachusetts Institute of Technology (MIT) suggest.
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Like 'a light illuminating the entrance porch of our planet', these powerful lights would be able to attract the attention of our potential extraterrestrial neighbours at a distance of up to 20,000 light-years. Not large enough to allow us to communicate with the galaxy closest to us, it would nevertheless cover a perimeter large enough to reach many star systems.
'It will be a real challenge, but not impossible,' says James Clark, co-author of The Astrophysical Journal. 'The types of lasers and telescopes we build today can produce a detectable signal, so that an astronomer could, when glancing at our star, realize that its light spectrum is unusual.'
Morse code in space
More concretely, the researchers propose to use a laser of 1 to 2 megawatts, focused thanks to a telescope of 30 to 45 metres wide. For comparison, the largest telescope today, the Gran Telescopio Canarias, is 10.4 metres wide and a 39-metre mirror is currently being built for it in Chile. With such measurements, it would be possible to create an infrared ray powerful enough to be noticed by an outside observer, without being surpassed by the energy emitted by the Sun.
According to the team, potential neighbours orbiting the famous Proxima Centauri or TRAPPIST-1 would be the most likely to perceive our messages. Of course, the project faces many safety, physical, economic and material limitations and remains for the moment in the realm of the hypothetical.
'Generally, this is just a feasibility study. Whether or not it's a good idea will be the subject of a whole new discussion in the future,' concludes Clark.
