For more than two decades, millions of desktop computers around the world shared their computing power while they were ‘at rest’ with a common goal. This was nothing more than searching for extraterrestrial technological signatures in the noise of the cosmos. Now, the team behind SETI@home has published the final analysis of its dataclosing a fundamental chapter in the search for extraterrestrial intelligence.
A cosmic funnel. The data analyzed by SETI@home come from observations made over 14 years using the iconic Arecibo Observatory in Puerto Rico. During this time, the project operated by collecting data while the telescope was targeted by other astrophysical research.
The immense amount of data recorded by this telescope was divided into small packages that were distributed over the Internet using the platform BOINC. In this case, more than five million volunteers lent the computing power of their PC processors to analyze these frequencies in the background with the legendary screensaver in the form of graphics with a latent pulse that crowned some PCs from the 2000s. All this thanks to a collaborative work that I started by installing a small application and giving up part of the processing power.
What was seen. The result of all this information was nothing other than statistical outrage. Specifically, more than 12 billion initial detections were identified, and volunteers from there looked for energy spikes, narrowband pulses and signals with repetitive structures over time.
The analysis focused on a 2.5 MHz band around the 1.42 GHz frequency, known as the hydrogen transition line, considered the logical “radio channel” for an interstellar civilization.
The sieve end. Finding an alien signal in that mountain of data requires, first, discarding our own technological screams that we have in space. The second phase of the project consisted of cleaning those 12 billion detections from radio frequency interference. Aviation radars, television stations or even mobile phones constantly pollute the radio spectrum, not allowing us to see what is in the background.
How it was done. The truly interesting thing about this project was how they managed to Separate the wheat from the chaff in a sea of millions of datasince the researchers designed complex algorithms with a very ingenious technique called ‘birdies’.
The ‘birdies’ are nothing more than software-simulated alien technosignatures that the team artificially injected into the database. Its importance lies in that they simply serve to test the sensitivity of the system, since if the anti-noise filters erased the ‘birdies’ or failed to group them, it meant that the algorithm was failing, since it would also be eliminating possible data that pointed to extraterrestrial life.
The result. In this way, the researchers were able to go from having 12,107,039,965 in their database to selecting 100 specific signals, which is where some type of communication with an extraterrestrial could be found. A titanic cleaning task, and it is where one of the most important points of all this research lies.
The role of China. The problem with all this is that the Arecibo radio telescope in December 2020 prevented the original source of the data from being able to verify these findings. Fortunately, the gigantic rFAST adiotelescope in Chinacurrently the largest and most sensitive of its kind in the world, has taken over for the final stage.
In this way, with a database of 100 signals and with 23 hours of observation time dedicated to the FAST, the different locations began to be re-observed. And it is not a quick process, since each re-observation at the Chinese telescope lasts about 15 minutes and includes a slow scan with the 19 beams of the FAST receiver. This is fundamental, because the sensitivity obtained in these new measurements is substantially better, reaching between 2.0 and 2.5 times the capacity of the original Arecibo data.
The outcome. After all this, the question seems obvious: Does this mean that we have finally contacted an extraterrestrial intelligence? We must be honest and emphatic: no. To date, none of the signals analyzed or reobserved have been shown to be a repeatable or conclusive alien technosignature.
However, from a technological and astronomical point of view, SETI@home has been a historic triumph, as it not only democratized computer science and pioneered the immense power of distributed computing for the masses, but it has established an open source framework and new documented sensitivity limits for the future. The use of high-computational birdie injection for end-to-end testing of analysis software is, in fact, a pioneering advance in radio astronomy.
Images | SETI@Home Leo_Visions
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