An alien civilization with sufficient power and motivation could arrange entire Solar Systems into resonant orbits with complex ratios - a concept woven into nature. It would probably not only be aesthetic but could also help ET advertise to distant searchers like us that they exist - without using radio signals or laser beacons.
Are we alone in the universe? Probably not. With all the fuss about UFOs in the last few years, it seems ever more likely that we are not the only species to have developed since the “beginning” of the universe. UFOs might be just evidence of that. However, we do not know for sure since the phenomenon has not been studied enough.
Our telescopes are pointed at the skies, and we continue exploring the vastness of space with state-of-the-art space telescopes like Hubble and Webb. We look at distant galaxies, faraway stars, and strange worlds in an effort to find someone out there.
The day we do, everything will change for us.
But how do we do that?
Is it enough to study galaxies and star systems, looking for chemical elements in their atmospheres that would point to a possible biosignature for life?
According to one group of researchers, we could actually look at planets, not their atmospheres but how they orbit their stars.
How Aliens could move entire planets in the solar system
An advanced alien civilization could reposition six or seven planets into a series of carefully-arranged orbits as a signpost advertising its presence. Mathematical thinking is all it takes to spot it.
A number of bodies move in resonant orbits around their parent bodies. Europa’s moon Io, for example, completes two orbits for every orbit Jupiter’s moon Europa completes. Each time Europa makes two orbits, Ganymede makes two, giving the two moons a 4:2:1 resonance. An entire fleet of planets can be found in resonance in K2-138, a planetary system far away in deep space.
Matthew Clement and his colleagues from The Carnegie Institution for Science Earth and Planets Laboratory write in the journal Monthly Notices of the Royal Astronomical Society that an alien civilization with sufficient power and motivation could arrange entire Solar Systems into resonant orbits with complex ratios – a concept woven into nature.
It would probably not only be aesthetic but could also help ET advertise to distant searchers like us that they exist – without using radio signals or laser beacons.
Clement and his colleagues, who simulated solar systems with several sets of resonance orbits, suggest that this is theoretically possible. Among them are those whose ratios spell out all prime numbers up to 11 and two other series of numbers called Lazy Caterers’ Sequences and Fibonacci Sequences.
In the simulations, the Solar Systems remained stable for 10 billion years, corresponding to the Solar System’s lifespan.
It is common for planets and moons to settle into resonant orbits naturally, such as the 4:2:1 resonance between Jupiter’s three innermost moons – or the more complex resonance that binds the TRAPPIST-1 worlds.
There are, however, some ratios that are more common than others. Physicists are particularly drawn to ratios like 4:3, 3:2, and 2:1, which are referred to as “first-order resonances” by astronomers because they differ by one.
A higher-order resonance, however, is much less common in nature, with ratios like 7:1 or 13:1. It would be a clear indication that something intelligent was involved if the ratios of those orbits matched up with Fibonacci sequences, which math nerds throughout the galaxy would recognize immediately.
Encoding math in the orbit of planets
In their paper, Clement and his colleagues write that extended chains encode abstract mathematical sequences, so detecting them would be quite intriguing.
The question is, what would you need to do if you were an advanced alien civilization that wanted to rearrange the orbits of planets in your star system?
In this study, Clement and his colleagues propose using something about the size of an asteroid to manipulate its planetary neighbors’ orbits by applying gravitational nudges.
Clement tells Inverse that this actually happens. “We are fairly confident that the Solar System’s giant planets moved around significantly after they formed, as they had repeated flybys with leftover debris and with stuff like Pluto.”
The idea of intentionally doing the same thing isn’t quite science fiction either. There have already been serious discussions about guiding an asteroid into a closer orbit for mining by gravitational nudges from another small object. Our spacecraft are already being sent into more distant orbits (or out of our solar system) using the same principle.
However, companion planets’ orbital architecture requires patience.
Not so soon
“It would take millions of years to have one asteroid or several asteroids move a planet-sized thing that [necessary] amount of distance,” says Clement. That’s an order of magnitude longer than our species has even existed. “But if you’re a more advanced civilization, maybe you could think on million-year timescales.”
A technologically advanced alien culture might be able to move a planet’s orbit by applying thrust to it. However, in terms of sheer energy requirements, Clement told Inverse that any civilization capable of harnessing the vast majority or all of the energy from its star could accomplish the task in just over two (Earth) years.
It depends on two things whether we can find intelligent aliens if we assume they exist somewhere in the galaxy: first, whether we are capable of detecting their breadcrumbs; second, whether the civilizations of those civilizations exist at the right time to be discovered. As Clement and his colleagues note, the solution to both problems may be in “the orbital architecture of companion planets.
The orbital periods of planets could be encoded if you wanted to create a system that would permanently communicate your existence, says Clement.
Spacecraft carrying golden records, radio messages, or giant orbiting platforms do not last as long as creative planet arrangements do.
As Clement points out, civilizations may only be able to broadcast themselves for a limited period of time.
In some instances, technology can outlive its creators — radio broadcasts will continue to be broadcast into space long after we are gone. The Lageos satellites will likely remain in orbit longer than Earth will remain habitable since they are very stable in orbit 5,900 kilometers above Earth.
However, even within a universe that is 13.8 billion years old, even relics that have a shelf life of a few million years can overlap with SETI programs on other planets.
If the planets in question are far enough from their stars to survive its final phase of life, Clement and his colleagues believe that Solar System-sized signposts will survive for at least 10 billion years.
As a species capable of building telescopes but not capable of moving entire planets around, a cosmic message embedded in the orbits of planets may also be one of the easiest signals to spot for species like us. This is because exoplanets can be measured easily by how long they take to orbit their stars.
So, a solar system that follows the Fibonacci Sequence might be perfect as an alien signpost, however farfetched it may sound.
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