The Drake equation is one of the most famous in astronomy. It has been discussed since Frank Drake first formulated it in 1961. The equation has served as an effective starting point for discussing how much life can be distributed throughout the galaxy. All equations can be improved, however, and an international team of astrobiologists and astronomers has succeeded.
What’s wrong with the Drake equation?
The Drake equation is a formula designed to determine the number of extraterrestrial civilizations in the galaxy that humanity has a chance to make contact with.
The formula looks like this:
N = R⋅fp⋅ne⋅fl⋅fi⋅fc⋅L
N is the number of intelligent civilizations ready to make contact;R is the number of stars formed per year in our galaxy;fp is the proportion of sun-like stars with planets;ne is the average number of planets (and satellites) with suitable conditions for the birth of a civilization;fl is the probability of life on a planet with suitable conditions;fi – the probability of the emergence of intelligent life forms on a planet with life;fc – the ratio of the number of planets whose intelligent inhabitants are capable of and seeking contact to the number of planets with intelligent life;L – the time during which intelligent life exists, can make contact and wants it.
The equation itself was centered around the search for radio signals. However, its formulation implies that people will find so-called “biosignatures” rather than technological traces of civilizations in the search. For example, astronomers might find methane in a planet’s atmosphere, which is a clear sign of life, even if that planet has not yet developed intelligence.
Biosignature is any manifestation of the effects of life that scientifically proves the existence of life in the past or present.Technosignature is any measurable property or effect that scientifically proves the existence of technology in the past or present.
That said, the very search for biosignatures was impossible when Drake wrote the equation. But now the situation has changed, especially with the launch of the James Webb telescope. Perhaps it’s time to change the original equation to better reflect the scientists’ new search capabilities. One way is to split the equation into two separate ones, reflecting the search for biosignatures and technosignatures, respectively.
According to a new study by University of Pennsylvania researchers, biosignatures are likely to evolve much more frequently than technosignatures. Logically, this follows from the fact that the number of planets on which a technologically advanced civilization develops is far less than the total number of planets on which life originally originated. After all, it took Earth about 4 billion years after the first life appeared to develop an intelligent civilization.
What does the equation look like now?
Scientists have modified the original equation by reducing the probability of the existence of a technologically advanced civilization to the product of two multipliers. The formula now looks like this:
A = Nast⋅fbt
A is the number of all technologically advanced species that have ever existed in the observable universe;Nast is the number of potentially inhabited exoplanets in a given region of the universe;Fbt is the probability of a technologically advanced civilization on a given planet.
Above is Drake’s equation in its usual form, below – the version that combines a number of parameters together.Photo: Rochester University
According to the new study, we’ve been looking for extraterrestrial life all wrong all along, focusing our attention on looking for biosignatures. And perhaps a focus on technosignatures will make things right.
Why is searching for technosignatures better?
One fundamental characteristic of technology is that while it can originate on a planet with a biosphere, it can leave it to remain. Thus, Earth has sent many signals, messages and probes beyond Earth and even the solar system. This significantly affects another factor in the Drake equation – L, or the length of time a signal is detected.
As the authors of the new paper point out, there are four factors that point to the advantage of finding technology from extraterrestrial civilizations.
Technology can outlive the biology that created it and even destroy the biosphere that created it. But it can still be detected, even at great distances. Depending on the reliability of the technology, this could be millions or even billions after civilization has died out.
Technospheres can potentially outnumber biospheres. For example, if lunar colonization advances steadily over the next few hundred years, the Moon will become a world without a biosphere, but will be distinguished by a technosphere.
The technology itself could become self-replicating, like the von Neumann probe. technosignatures could exist without a planet at all, in the form of spacecraft or satellites. In fact, it may even be their most common form in the Galaxy. Thus, the limiting factors of the Drake equation, which are directly related to the planet, are not applicable to technosignatures.
Another factor affects how easy it will be to find biosignatures compared to technosignatures – how detectable they are. The authors of the study note that detecting biosignatures is a challenge – in fact, we currently cannot even detect Earth’s biosignature at the distance of Alpha Centauri, the closest star system to us. Data from the James Webb telescope may help. Even so, radio astronomy projects like the Square Kilometer Array are much better suited to detect clear signs of technology.
There’s a problem
To find both types of signatures, it’s difficult to separate the right signal from the “noise,” which can take many forms. For example, distorted spectral analysis or thermal signatures. However, in the article, the authors of the study convincingly argue that technosignatures, at least, can be much clearer than any biosignatures.
What’s the bottom line?
All this means is that perhaps scientists have been focusing on “the wrong thing” for the past few decades. Instead of looking for signs of life in the past and present, we should pay more attention to looking for technosignatures. In any case, the search for extraterrestrial intelligence should continue. It is much more likely that humans will find signs of a technologically advanced civilization. Even if it is already extinct, leaving behind only a final message.
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