“The longevity of technological civilizations is unknown, as is the probability of less advanced societies becoming technological. Accordingly, searching for pre-industrial extra-terrestrial societies may be more productive.”
The quest to identify UFOs as vehicles from other planets assumes that the beings inside of them are more intelligent than us, since they’ve already mastered space travel. The same is often true of the search for signs of extraterrestrial intelligence (SETI) which looks for intelligent communications or, more recently, signs of industrialization on exoplanets that would indicate life at least as advanced as modern humans. As a recent article in the International Journal of Astrobiology points out, this ignores the vast majority of planets that may have life forms not advanced enough to create industrial pollution chemicals in quantities that can be picked up by our telescopes (assuming you consider pollution to be a sign of intelligence). Authors and astronomers Andrew Lockley of University College London and Daniele Visioni of Cornell University are trying to find ways to locate those beings.
“Common alien societies might be more like the Inca, or the Elizabethans. These primitive societies were around for a lot longer than we’ve had radio.”
In a Cambridge Core blog post, Lockley postulates that these aliens could be like the humans who lived for 100,000 years prior to the Industrial Revolution – namely, farmers or hunter-gatherers. How do you spot farms on planets even just a few light years away? He and Visioni propose tuning telescopes to search not for chemical signatures but for subtle changes in the brightness and color of a planet’s surface. Massive fields of crops might show up, followed by changes that suggest harvesting. But how does one see prehistoric activities?
“Humans have been extensively modifying the environment for timescales around a hundred thousand years – with aboriginal fire clearance in Australia being a good example. Another example of primitive societies drastically modifying the landscape is extinction. Loss of species, such as the mammoth, often triggered huge ecosystem change. Similarly, introduction of invasive species can change the landscape – like rabbits did, in Australia. These large-scale changes are clearly visible from space – and this may also be true over interplanetary distances, given favorable circumstances.”
That makes sense. Other activities that could cause subtle color changes over huge areas are overgrazing of ET forms of livestock, changes to liquid flows for irrigation that cause massive floods, and even just mass migrations that leave trampled ground and massive waste in their wake (again assuming they’re like humans). The authors also speculate that, while these civilizations may not be industrialized, they might still have the capability to study the stars as we do – an activity that might turn them on to the existence of other intelligent life forms … like us. What if they want to signal us? Or they panic and decide they don’t want to be visited or even found? They may make visible changes to send a message or camouflage themselves.
“Right now, no telescope is sensitive enough [to make these observations]. But future candidates like CHEOPS, an optical photometric space mission by the European Space Agency, might be.”
In an interview in The Sun, Visioni instructs that new telescopes should be designed to search for planets with large continents orbiting small, dim stars that would not interfere with seeing light reflected off of surface changes caused by life forms.
Finding ETs still in their civilization’s stone age might not be as exciting as meeting one piloting a starship, but which one would we have a better chance of not being conquered by?