Scientists are also looking for signs of alien technology, like Dad first did with Project Ozma. Originally defined in the equation as the fraction of civilizations that develop ‘communication technology’, many SETI scientists today envision a broader definition that includes any manifestation of extraterrestrial craft, such as radio waves, optical laser beams or energy harvesting mega-infrastructures.

To reflect this range of possible signals, Tarter coined the term “technosignatures,” and she says such detection would likely be much less ambiguous than picking up clues in alien atmospheres or looking for fossilized microbes. As the next generation of Earth’s keen-eyed telescopes come online, Tarter and other SETI scientists hope to use computer programs to sift through mountains of incoming data, looking for something unusual or abnormal – a way to find technosignatures that we may not have. even imagined.

“We could be totally caught off guard by something that turns out to be a fortuitous signal from a completely different observing program,” Tarter said.

Solving the final variables (the fraction of the worlds with life, intelligence, and technology) will require more than just detection. As with exoplanets, multiple observations will be needed to reveal how common life is in the galaxy.

“With life we ​​tend to think, Oh man, if we find out about it in one place, it’s gonna be so revolutionary. Of course we will, but again, if we find it in one place, we haven’t gone from ignorance to substantial knowledge, ”Grinspoon says.

“So even though we get a signal next Friday, it’s not like we don’t need the Drake equation anymore.”

The most delicate variable

Dad has often said that the last variable in Drake’s equation, L, is the most upsetting. L is the average length of time that civilizations are detectable – a definition that is often confused with survival or extinction, but not necessarily related to either.

“It is unfortunate that people refer to the term longevity as the longevity of a technological civilization. It’s not that. It’s the longevity of the emission mechanism, ”says Tarter. “We could actually build something, a kind of technosignature, that has a longevity far beyond that of our civilization.”

Because L is an average, even an incredibly long alien transmission could dramatically change its value – for example, if a civilization found a way to radiate its presence in the galaxy for billions of years, perhaps for the sole purpose of ‘help others. in search of cosmic companions.

“Since everything in the equation has the same weight, I knew the answer would be as good as the thing we knew the least,” Dad once told me. “L is definitely the thing we know the least about. “

Unlike the other variables, the value of L also depends on the detection capabilities of the civilization performing the research. Humans can search for technosignatures by studying a variety of electromagnetic signals; if a civilization like ours observed Earth, it would first see tweets from military radars issued in the early 1900s. But a civilization with superior detection capabilities might look for finer clues.

Aliens who figured out how to read technology signatures in planetary atmospheres, for example, may have been able to sniff out emissions released during the Industrial Revolution in the mid-1800s – a detectable technosignature if you know what to look for and have the patience to watch a planet slowly change. Civilizations with even more advanced technology could quietly watch life emerge and roam many planets, sometimes failing, other times prosperous.

Humanity does not yet have this power, and there is no guarantee that our species will survive long enough to perfect the art of finding alien life. But one day, if we persevere, we can finally make contact.

Life itself

The prospect of super-intelligent aliens looking for us is a captivating thought to ponder as I gaze at the thick, millennial redwoods that surround me and my father in our little corner of the California forest. Over the course of a millennium, these trees have quietly witnessed countless lives unfold beneath them, countless struggles for existence, countless new survival strategies. For long-lived civilizations – the ancient oaks of the galaxy – the value of L, at least in theory, is huge.

Advanced human civilization may just be an accident in the Age of the Universe, but Dad thinks it’s just a matter of time and enough willpower before he finds any evidence that the galaxy is. populated by smarter beings, whatever form they might take.

“We don’t know what we’re looking for,” says Wright. “We’re our only example of the thing we’re sure to seek out. “

On the contrary, the most enduring legacy of the Drake equation is not a digital solution, but a mirror: it asks us to think of Earth and humanity from a cosmic point of view, to be considered the fragility of our existence in this galactic sea.

“Its durability, longevity, persistence, the reason it persists, the reason we keep using it, the reason it keeps showing up, is because it’s a great guide to the whole problem of life in the universe, ”says Wright. “It’s a very versatile equation in that it allows you to explore all kinds of aspects of life and humanity, depending on which term you want to get hooked on. “