News about the probable existence of extraterrestrial life and our chances of detecting it are usually positive. We often hear that we can discover it at any time. In September 2023, we were told that it was “only a matter of time” before life would be found beyond Earth. In September 2024, the headline read: “We are close.”
It's basic to see why. Headlines like “We're probably not close” or “Nobody knows” aren't very clickable. But what does the relevant expert community actually think, taken as a whole? Are positive forecasts common or occasional? Is there any consensus at all? We found out about this in our fresh paper published in Nature Astronomy.
Between February and June 2024, we conducted four studies on the likely existence of basic, convoluted, and smart extraterrestrial life. We sent emails to astrobiologists (scientists who study extraterrestrial life), as well as scientists in other fields, including biologists and physicists.
A total of 521 astrobiologists responded, and we received 534 non-astrobiologist responses. The results show that 86.6% of astrobiologists surveyed answered “agree” or “strongly agree” that it is likely that extraterrestrial life (at least a basic kind) exists somewhere in the universe.
Less than 2% disagreed and 12% remained neutral. Based on this, we can say that there is solid agreement that extraterrestrial life exists in some form somewhere out there.
Scientists who were not astrobiologists generally agreed, with an overall agreement score of 88.4%. In other words, it cannot be said that astrobiologists are more likely to believe in extraterrestrial life than other scientists.
When we move on to “complex” extraterrestrial life or “intelligent” aliens, our results were consistent with 67.4% and 58.2% for astrobiologists and other scientists, respectively. Therefore, scientists tend to think that alien life exists, even in more advanced forms.
These results are even more significant because the disagreement for all categories was low. For example, only 10.2% of astrobiologists disagreed with the statement that smart aliens probably exist.
Optimists and pessimists
Are scientists just speculating? Typically, we should only pay attention to scientific consensus when it is based on evidence (and there is a lot of it).
Since there is no relevant evidence, scientists are left to guess. Scientists, however, had the option of voting “neutral”, which some scientists chose, feeling that they would be speculating.
Only 12% chose this option. In fact, there is a lot of “indirect” or “theoretical” evidence for the existence of alien life. For example, we already know that habitable environments are very common in the universe.
We have several of them in our solar system, including in the subsurface oceans of the moons Europa and Enceladus, and probably also in the environment a few kilometers below the surface of Mars. It also seems significant that Mars was once a habitable place, with lakes and rivers filled with liquid water and a significant atmosphere.
It is reasonable to generalize from here to the truly gigantic number of habitable environments throughout the galaxy and the wider universe. We also know (since we've been here) that life can come from non-life – after all, it happened on Earth.
Although the origins of the first uncomplicated forms of life are poorly understood, there is no compelling reason to believe that they required astronomically occasional conditions. And even if this happens, the probability of life arising (abiogenesis) is clearly non-zero.
This will assist us look at the 86.6% compliance rate in a fresh lightweight. This may not be a surprisingly powerful consensus after all. Perhaps this is a surprisingly feeble consensus. Let's consider the numbers: there are over 100 billion galaxies. We also know that habitable environments are everywhere.
Suppose there are 100 billion billion habitable worlds (planets or moons) in the universe. Suppose we are so bleak that we think the chance of life starting on any habitable world is one in a billion billion.
In that case, we would still respond “agree” to the statement that it is likely that alien life exists in the universe.
So optimists and pessimists should have responded to our survey with “agree” or “strongly agree,” with only the most radical pessimists disagreeing about the origins of life.
With this in mind, we could present our data in a different way. Let's assume we ignore the 60 neutral votes we received. Perhaps these scientists thought they would be speculating and did not want to take a position.
In this case, it is wise to ignore their votes. This gives a total of 461 votes, of which 451 were in agreement or strongly agree. Currently, the overall compliance rate is 97.8%.
This move is not as illegal as it seems. Scientists know that if they choose the “neutral” option, they cannot be wrong. Therefore, it is a “safe” choice. This is often called “satisfactory” in research.
As geophysicist Edward Bullard wrote in 1975, when debating whether all continents were once connected, instead of making a choice, “it is wiser to remain silent, … to sit on the fence and wait with manly ambiguity for more data.” Not only is staying still a safe and sound choice for scientists, it also means the scientist doesn't have to think too challenging – it's an basic choice.
Getting the balance right
We probably want balance. On the one hand, we have the lack of direct empirical evidence and the reluctance of responsible scientists to speculate. On the other hand, we have evidence of a different kind, including a truly gigantic number of habitable environments in the universe.
We know that the probability of life originating is non-zero. Perhaps, all things considered, 86.6% agree, 12% neutral, and less than 2% disagree is a reasonable compromise.
Perhaps – given the satisfaction issue – when presenting such results, we should present two results for complete agreement: one including neutral votes (86.6%) and one excluding neutral votes (97.8%). No result is a single correct result.
Each perspective addresses different analytical needs and helps prevent oversimplification of data. Ultimately, providing both numbers – and being lucid about their context – is the fairest way to convey the true complexity of the answer.
Peter Vickers, Professor of Philosophy of Science, University of Durham; Henry Taylor, Associate Professor, Department of Philosophy, University of Birmingham and Sean McMahon Reader in Astrobiology, University of Edinburgh
This article has been republished from Conversation under Creative Commons license. Read it original article.
Image Source: Pixabay.com
