The Examination of Space: Review: Starlight

The equation most famous in astrobiology is something of a Rorschach test. The Drake equation, developed more than half a century ago, calculates the number of intelligent civilizations in the galaxy according to a series of astrophysical, biological and other factors, of the fraction of planetary stars to the lifetime of a technological civilization. But, since so few of these factors are known to an acceptable level of accuracy, it is easy to use the equation to find the answer you want about the abundance of extraterrestrial civilizations. We think we are alone in the galaxy? Put in a few pessimistic values ​​for these variables and the answer falls to one-us-or even less. You think the galaxy teems with life? Just turn the buttons in the other direction, and the answer skyrockets.

However, the uncertainty on some of these factors, mainly astrophysical, is declining. This gives the astrophysicist Adam Frank the confidence needed to rework Drake's equation in another format that focuses on what he calls the "bio-technical probability" of creating the same. an intelligent life. "In other words, what were the chances that our civilization was the only one?", He writes in a chapter of his new book, Light of the Stars . "Put in the exoplanets data, we found the answer to 10 ^-22 be one out of ten billion billion."

This theoretical confidence that we are not the only civilization in the universe – not supported, of course, by any real evidence of extraterrestrial civilizations – is a key element of Frank's book, which he describes as being "the astrobiology of the Anthropocene", the term coined in recent years for a new era where humanity has long-term effects on the planet. If we are not the only civilization, others may have gone through their own version of the Anthropocene: what lessons do they offer us?

However, they can not offer us directly because we do not know any civilization. Instead, Frank and his colleagues developed models of growth and collapse of civilizations, based on the use of energy and the effects on global temperature. In many cases, they found that civilizations suffered massive "murders" or large-scale collapses, even when they moved from "high-impact" energy sources (fossil fuels) to springs. low impact like the wind and the sun. . "In these cases, the own dynamics of the global environment was the culprit," he writes. "Push a planet too hard, and it will not come back where it started."

Much of the book is an accumulation at this conclusion. Several chapters deal with Drake's equation and the quest for extraterrestrial intelligence, how the missions to Venus and Mars helped us understand how the climates of planets can change dramatically with time, the climate of the Earth and its biosphere and the search for exoplanets. These chapters include a series of vignettes with people involved in space missions or research on the study of our own planet and the search for life beyond.

In the end, however, this approach to "astrobiology of the Anthropocene" is unsatisfactory. There are interesting arguments in the book on the likelihood of a smart life elsewhere in the universe, and a compelling argument that human activities alter the climate with significant and deleterious effects in the years and decades to come up. But the combination of both seems forced and useless. It's hard to see how models of hypothetical extraterrestrial civilizations will convince people to act to protect our planet. Why not model our own world, which we know infinitely better?

There is also, at times, almost an arrogance in Frank's arguments about extraterrestrial life. "It is up to the naysayers to demonstrate how, with so many worlds and so many possibilities over the whole of cosmic space and time, we are in some ways the first and the only ones," he writes. But this is not how science works: it is not up to the "opponents" to prove a negative – there is no other intelligent life in the world. universe – but rather to scientists like Frank to find evidence of such a life. And, until now, this research has become empty: we are the only life, intelligent or otherwise, known to exist. Perhaps, in the decades to come, we will find evidence of primitive life past or present on Mars, Europa or Enceladus, or biosignatures on a distant exoplanet. Or, eventually, a SETI search will finally find a signal of extraterrestrial origin. However, it is up to scientists to find this evidence to prove the existence of life beyond Earth, not "detractors" to prove that this is not the case.

Whether or not other civilizations exist has little bearing on our future. If we find them, it is unlikely that they will land on the National Mall carrying gifts or transmit an Encyclopedia Galactica with solutions to all our problems. And if we do not do it – perhaps because the lifespan of these other technological civilizations proves remarkably short – it does not condemn our world to the same fate. If we want to preserve our civilization from the Anthropocene, it is up to us to do it, no matter if we are the only intelligent species in the universe, or one of the trillions. The solution, dear reader, does not lie in the stars but in ourselves.

Jeff Foust ([email protected]) is the editor and editor of The Space Review, and a senior writer of SpaceNews. It also operates the Spacetoday.net website. The views and opinions expressed in this article are those of the author alone.

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