Debrief looked recently at five places for hiding “technosignatures.”
Technosignatures are evidence of the activity of intelligent agents, as opposed to events or materials that the laws of nature alone can explain. They might include “radio signals, city lights, atmospheric changes like CO2, and free-floating spacecraft.”
Or, reaching back into the past, they might be engravings on bone from 51,000 years ago or a child’s burial from 80,000 years ago. Technosignatures are events and entities that nature did not simply generate without some form of thought as a necessary ingredient.
If we assume that extraterrestrials want to surveil without being noticed, here’s one of the five venues they might pick — a Lagrange point:
Lagrange points are stable places in the orbit of a planet where debris or spacecraft can remain stable for a long time. “If any extraterrestrial astronomers sent an exploratory spacecraft to our solar system, then the Lagrange points are all possible destinations to send such a spacecraft,” Haqq-Misra told The Debrief.
Lagrange points are so stable, spacecraft that need to remain in position use them to reduce fuel consumption. Things that go there tend to stay there due to the gravitational pull, according to NASA.
Lagrange points aren’t always used on purpose to save on gas; a guest floating through could get stuck there too.
“An extraterrestrial spacecraft in the solar system might also be defunct and broken, having completed its primary mission, and so the drifting debris might also end up in one of these stable Lagrange points,” Haqq Misra said.
[Astrobiologist Jacob] Haqq Misra advises you’ll want to look specifically for shiny things (or any physical reflecting objects) and use a telescope that can observe at optical wavelengths and infrared wavelengths to see if there is any heat loss.Sarah London, “The top 5 places in our solar system astrobiologists say aliens would be hiding their technology” at The Debrief (September 27, 2021)
More from NASA on Lagrange points: “These points in space can be used by spacecraft to reduce fuel consumption needed to remain in position.”
Earth–Moon orbits, using the Sun as a telescope, the Oort Cloud, and the edge of the solar system are also candidates, as London explains.
One thing that helps the search is that we are looking for evidence of intelligent manipulation of the environment — which is what we always look for when we are tracking the presence of other humans. At least we know how to do that in principle.
You may also wish to read: Data analyst offers 15 reasons extraterrestrials aren’t seen. He estimates that there should be 100,000 civilizations in our galaxy. Some of Yung Lin Ma’s suggested reasons are ones we had not considered before, including flow of time and communication differences.