PENN STATE (US) — Why have we never found evidence of extraterrestrial probes in our universe? A new study suggest that, from a mathematical point of view, we have not looked in enough places.
“The vastness of space, combined with our limited searches to date, implies that any remote unpiloted exploratory probes of extraterrestrial origin would likely remain unnoticed,” write Jacob Haqq-Misra and Ravi Kumar Kopparapu, two postdoctoral researchers at Penn State, in a paper posted online on ArXiv.
The Fermi paradox, originally formulated by Enrico Fermi, asks, if intelligent life is common, why have no technological civilizations been observed. Answers could include life is rare, intelligent cultures inevitably destroy themselves, intelligent beings have not gotten here yet, or they are here but not revealing themselves.
Even without actual contact, other civilizations could be sending unpiloted probes to quietly peek at our civilization.
The probes, like ours, would be small and might be hidden in a variety of places. In the asteroid belt they would probably go unnoticed, especially if these nonterrestrial objects are only 3 to 33 feet in size, weighing little more than a ton.
“Extraterrestrial artifacts may exist in the solar system without our knowledge simply because we have not yet searched sufficiently,” write Haqq-Misra and Kopparapu. “Few if any of the attempts would be capable of detecting a 1 to 10 meter (3 to 33 foot) probe.”
The researchers used a probabilistic method to determine if scientists have looked closely enough anywhere in the solar system to definitively say nonterrestrial objects exist.
The analysis is based on answering the question, how sure can we be that we should have already found any nonterrestrial objects lurking in the solar system.
They view the solar system as a fixed volume and figure out the percentages of that volume that would need to be thoroughly searched using a discovery capability small enough to detect these probes, assuming that the probes are not consciously camouflaged. The researchers note that most searches to date have not been fine enough to locate such small probes or to totally rule out anywhere.
After taking into account a variety of potential biases, such as “the universe is teeming with life” or “life is rare,” the team developed an equation that can be applied to a portion of the volume of the solar system and determine whether sufficient searching has been done to ensure that we can say there are no nonterrestrial objects within that volume.
“The surface of the Earth is one of the few places in the solar system that has been almost completely examined at a spatial resolution of less than 3 feet,” they say.
But even as humans have spread across the solid surfaces of the Earth, there are still caves, jungles and deserts as well as the ocean floor and subsurface areas that have not been explored. Even with this, the Earth does have a high confidence that no nonterrestrial artifacts exist.
The Moon and Mars have been searched to a small extent. An ongoing mapping project, the Lunar Reconnaissance Orbiter, is looking at the moon at a resolution of about 20 inches, so scientists may eventually be able to determine if there are nonterrestrial objects on the moon, but surface maps may not be sufficient to distinguish between a space probe and a rock.
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