The dark forest theory: is sending messages into space a very dangerous idea?

Space exploration is one of the most exciting endeavors humanity has undertaken, but it is not without its risks.

Imagining the Voyager 1 probe's journey through space when humanity no longer exists
The history of the five NASA spacecrafts that travel beyond the Solar System

The possibility that other forms of life exist on worlds other than our own has long fascinated astronomers. In fact, various space programs are aimed at detecting potential signs of life on other worlds —not only through the possible physical discovery of such evidence by spacecraft, but also by searching for signals that other, civilized worlds might have sent into space. The well-known SETI program, for instance, relies on the analysis of radio waves and laser pulses that such beings might have transmitted.

Another way to carry out such exploration is to communicate our presence on Earth. Several space probes have carried messages in the form of plaques or discs, with the hope that any civilization that finds them might learn of our existence —what we are like and where our home is located within the vastness of space. Furthermore, signals have been sent into space from various locations. The most famous of these are the messages transmitted by the Arecibo radio telescope on November 16, 1974—a 1,679-bit sequence describing our physical form and our location. They were directed toward the M13 star cluster, situated 25,000 light-years away; consequently, if anyone were to ever respond, it is highly likely that the reply would arrive only after humanity had already ceased to exist.

In October 2017, the scientific association EISCAT sent a message into space from Tromsø, Norway, as part of a program known as Active SETI. This signal was directed toward the exoplanet Luyten b (GJ 273b), located 12.4 light-years away. If intelligent life exists on that world, the earliest a response could arrive is in 2042. This raises a question regarding such programs: could sending messages into space be dangerous? The civilization that receives them might be friendly—but then again, it might not. This is the premise of the "dark forest" theory, which is explored in depth in a video recently published by the YouTube channel Abismo (the video is in Spanish but has an English audio track; you can enable it in the player):

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Photo: Rosie Sun.