Intelligent alien societies may be scattered across the galaxy and beyond – but scientists say they are ‘too advanced’ to spot.
Researchers used an unconventional method to find signs of extraterrestrial life – looking for the reflection of sunlight off solar panels after observing a similar phenomenon on Earth.
In a paper published in The Astrophysical Journal this summer, scientists focused on potential “Earth-like exoplanets.”
Previous attempts to locate our alien neighbors have focused on detecting biosignatures, or features indicative of life on a planet.
However, “technosignatures” – or observations of extraterrestrial technology – have taken precedence over the past two decades.
This includes elements like nitrogen dioxide pollution, chlorofluorocarbons, nightside city lights, and evidence of agriculture.
Scientists in this particular study sought evidence of silicon-based solar panels.
“Technological civilizations may harness their host star’s radiation for their energy needs, just like our civilization has commenced with large-scale solar photovoltaics,” the paper reasoned. “Most solar cells use silicon in different forms.”
Silicon solar panels were a fitting choice, as previous research found they reflect ultraviolet light more than other wavelengths.
As space imaging detects changes in wavelengths, this would make the solar panels visible to scientists on Earth.
However, the team quickly encountered a problem.
They found that a civilization harnessing solar power would be nearly impossible to detect, as solar energy is too efficient.
Researchers determined that 23% of the land on an alien planet would have to be covered with solar panels to be noticed in the expanse of space.
They began by calculating how much of Earth‘s land would be put aside to generate enough solar energy.
The researchers arrived at a meager 2.4% based on 2022 population statistics – even if solar power was the only energy source.
A global population of 10 billion – the maximum number the planet can sustain, according to the United Nations – only bumped the figure up to 3% land coverage.
Even 30 billion energy-hungry people would require less than 9% to sustain their demanding lifestyles.
The scientists deduced that a densely populated exoplanet wouldn’t need nearly three times the land coverage.
Moreover, “several hundreds of hours of observation time” would be needed to locate that 23%, making it an inefficient technosignature.
The scientists ultimately concluded that their efforts would be better spent on other methods.
They noted that their findings also reexamined the practicality of concepts like a Kardashev type I civilization or a Dyson sphere.
Both of these concepts involve alien civilizations harnessing renewable energy.
The Kardashev scale was devised in 1964 by Russian astrophysicist Nikolai Kardashev, who described a type I civilization as one at a technological level “close to the level presently attained on the Earth.”
A Dyson sphere is a hypothetical, super-advanced structure that cages a star and captures significant energy.
While the concept seems far-fetched (and is actually lifted from the 1937 novel Star Maker), scientists haven’t shied away from exploring every possibility.
Another paper published in May identified seven stars in our galaxy as those most likely to harbor Dyson spheres.
However, the latest findings put this idea in jeopardy.
The findings also call into question a crucial aspect of the Fermi paradox, which describes the contradiction between the likelihood of alien life and the lack of evidence supporting it.
If advanced extraterrestrial civilizations exist, they may be so far ahead of us that they don’t rely on solar or stellar energy.
Perhaps, the researchers wrote, “we have not discovered any large-scale engineering yet…because advanced technologies may not need them.”
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