Even if signals from technological civilizations reached our region, they may not have been detected due to limitations in range, duration, and intensity. The researchers conclude that the chance of detection will increase mainly with prolonged searches over greater distances.
A new paper proposes a statistical framework for understanding the ongoing silence in SETI searches, suggesting that even if signals from technological civilizations reached our region, they may not have been detected due to limitations in range, duration, and intensity. The researchers conclude that the chances of detection will increase primarily with prolonged searches over greater distances.
Since the beginning of the SETI search in the 1960s, astronomers have been trying to detect signs of the existence of technological civilizations beyond Earth. For decades, various regions of the Milky Way have been scanned in search of artificial radio broadcasts, laser flashes, or unusual infrared emissions, but so far no confirmed signal has been received. New research by theoretical physicist Claudio Grimaldi of EPFL suggests examining the question from a slightly different angle: not only why a signal has not yet been detected, but what can be concluded from the possibility that signals have already reached Earth's environment and escaped detection.
Technology signatures
The article, published inThe Astronomical Journal , deals with technological signatures, that is, any observable sign that could indicate advanced technology that is not of natural origin, for example artificial radio transmissions, directed laser beams or heat emissions from excess energy of large engineering structures. However, for such a signature to be detected, it is not enough that it reaches Earth. It must also be strong enough, appear in the frequency range that we are examining, and last long enough to be picked up by the observation instruments. Therefore, in principle, such signals may have passed here in the past without astronomers being able to detect them.
Grimaldi used a Bayesian model to relate three main variables: the number of signals that may have crossed Earth's orbit since 1960, the typical lifetime of such technological signatures, and the distance from which existing or future instruments could detect a signal. The model accounts for both signals that spread out in all directions, as well as more focused signals, such as beacons or laser beams. In this framework, Earth is considered to have received a signal when the signal passes through its location, but actual detection only occurs if the signal remains within the range and strength appropriate for measurement.
The main conclusion of the study is that there is no reason to assume that the detection of a nearby signal is an expected event in the immediate term. According to the calculations, in order to have a high probability of detecting technological signatures at a distance of only a few hundred or a few thousand light years, it is necessary to assume that a very large number of signals have already passed by Earth without being detected. In some scenarios, the required number even becomes so large that it seems unreasonable in relation to the number of possible life-supporting planets in this region of the galaxy. Therefore, the study indicates that the chance of discovery becomes more real especially when the search is extended to distances of thousands of light years.
Even in this scenario, caution is needed in drawing conclusions. The study does not claim that such signals have been detected or even necessarily exist, but only that within the framework of the statistical model, the lack of detection so far is not particularly surprising. If technological civilizations exist in the Milky Way, and if they emit detectable signatures, they are likely to be rare, distant, or emit long-range signals that are not numerous. Hence, continuing the search requires a more patient strategy, based on long observations, wide sky coverage, and continuous improvement of the sensitivity of instruments.
In this respect, the contribution of the study is not in declaring the possible discovery of aliens, but in attempting to quantify in a more sober way the conditions for discovery. He mentions that even in the absence of positive findings, one can learn from the silence itself about the scope of the search required. Instead of expecting a clear and imminent signal in the near future, the article suggests viewing the search for technological signatures as a long-term task, in which even the lack of discovery is a scientific fact that must be interpreted with caution.
for the scientific article DOI: 10.3847/1538-3881/ae394b
More of the topic in Hayadan:
- Seti scientists deny that Seti@home antennas detected an alien signal
- SETI searches for technology signatures: The hunt for extraterrestrial signals at the heart of the Milky Way begins
- They stop looking for radio signals from aliens - the SETI telescope array is closed due to lack of budget
- What is the maximum size of a planet? After discovering huge gas giants, it's hard to know
