One of the biggest problems facing the Search for Extraterrestrial Intelligence is that
we really have little idea of what one would look like.
This makes the prospect of detecting them difficult, after all, how do you look for
something that you haven’t ever seen before?
But there are clues, mainly based on things our own civilization does, or could do in
the future that gives us at least some kind of insight on what to look for as far as an
exocivilization is concerned.
Almost invariably, this involves detecting their technology.
So here are ten ways we might spot an alien civilization based on their technological
activities and, as a result, what they might be like.
Number 10.
Dyson Swarms and Energy Collectors
If we ever detected a Dyson swarm, which is possible through studying the light curves
of stars, it would indicate a very energy hungry civilization.
The idea is to build solar energy collectors in space to collect as much energy as possible
from a star.
The amount of recoverable energy from a star is mind boggling; far, far more than we currently
as a civilization can even dream of needing.
So if we did detect this, it would be a civilization of immense power.
If they could direct all the energy they were collecting from a star, depending on how much
of it they were collecting, they could devastate entire planets from light-years away.
They would also have immense amounts of energy for use in computing or space exploration
or very advanced scientific experiments.
But it may also be that because we haven’t yet seen any indication of this kind of a
technosignature, it could be that no civilization ever needs this level of energy generation,
much less than the available energy of an entire galaxy as in a hypothetical Kardashev
Type III civilization.
Number 9.
Odd Chemicals in their Atmosphere
This option may indicate a civilization that doesn’t really have that much energy, and
in fact it may possibly indicate a civilization that’s in trouble.
The case can be made that any advancing technological civilization will deal, at one time or another,
with climate change and the addition of industrial chemicals to atmospheres, such as CFCs.
We ourselves have done this, and this could be a common consequence of advancing energy
production and industry, where they’ve pushed their home world just a bit too far, and as
a result have to mitigate climate change artificially, something that we may well have to do.
But the opposite may also be true.
Civilizations may also intentionally terraform their worlds through the introduction of artificial
CFCs as an aid to induce a powerful, very fast greenhouse effect far more efficiently
than gases like carbon dioxide can do.
This would be an easily detectable technosignature, and would also be one of the few dead ringers
that indicate the activities of an alien civilizations as opposed to anything nature would produce.
Number 8.
Outgoing Aliens
In SETI, the greatest hope for discovery is something that’s easy to detect from proactive
aliens that want to be seen.
One way this could be done is if an exocivilization has built a huge, unambiguous radio beacon
that blasts out the interstellar equivalent of screaming hello.
But that’s not a cheap way of doing things, and it’s not the only way to create visibility
in the galaxy if your aim is to deliberately be discovered by other civilizations.
If one wants to be the life of the party in the milky way, cheaper possibilities might
be to construct giant objects in your star system that transit across the face of your
star, such as a louver arrangement advanced by astronomer Luc Arnold, or a huge opaque
triangle or other such shape that nature simply would not produce in a solid object, thereby
informing the rest of the galaxy that they are not alone if their astronomers are studying
photometry, as ours do.
Other hypothesized methods of saying hello include adding unusual elements into a star,
such as plutonium, that at least as far as we know, do not normally occur in nature in
large amounts, though this is now debated.
An example of this is Przybylski’s star, which shows evidence of transuranic elements
in its spectrum; were they put there deliberately, or did this star get bombarded by a neutron
star relatively recently, thereby providing a way for transuranic elements to exist naturally
in a star.
No one knows, but there’s also currently no sign of a neutron star in the vicinity.
But would those kinds of technosignatures actually say hello?
Might such a civilization not be the life of the party, but something much more grim.
The case could also be made that a civilization building enormous Arnold structures might
also be saying that they can build enormous megastructures of unknown use, including those
of a defensive, or offensive nature.
Or what might Pryzbylski’s star say, if the cause of that star’s odd spectrum isn’t
some natural phenomenon that we haven’t thought of yet, then is it a hello, or is
it informing the galaxy that whoever might be there has very advanced nuclear physics,
enough to fill their star with plutonium.
Imagine what a civilization could do in a situation of warfare.
One man’s hello in the galaxy, might in fact just be a warning sign for everyone to
stay away.
Number 7.
Star Movers
Seemingly one of the biggest projects one can do in this universe on a galactic scale
is move stars around.
While this may seem to be an impossible task, it might not be for a highly advanced exocivilization.
One concept for moving a star is called a Shkadov thruster and essentially involves
the construction of a partial dyson sphere to reflect radiation pressure from a star
unevenly to create thrust.
This then, over time, will move the star to wherever you wish it to go.
This is of course a highly speculative technology, and suffers from many of the pitfalls of a
full on Dyson shell around a star; how does one engineer a structure like that?
But if it is indeed possible to do it, then moving stars could have significant advantages
for an exocivilization.
One of these would be to arrange stars, you could arrange them into ideal positions to
facilitate travel between colonized systems, or move passing stars in for colonization
as needed.
It’s hard to say what the cost vs. benefit of such an undertaking would look like, but
it is in principle possible.
This would also be readily visible as a technosignature.
A huge shkadov thruster should be readily evident in a light curve for example, as would
oddly moving stars in general, or stars arranged in, say, geometric positions.
And there is one last possibility that might raise some eyebrows, and make a bit more sense
as far as the use of Shkadov thrusters go.
Clearing your galaxy of dangerous stars.
Giant stars tend to live short lives and come to violent ends and can affect nearby inhabited
systems.
An option for a galaxy spanning type III civilization to mitigate this might be to eject these kinds
of stars from their galaxy, or engineer the stars themselves to be less of a threat.
Either way, this would create a galaxy strangely devoid of certain classes of star, and leave
it reddened in emissions.
Such galaxies are known, but there are a lot of natural ways this could happen as well.
At any rate, such a galaxy may show no other signs of being inhabited, this would be SETI
at very long distance, but the idea of a civilization managing galaxy is at least an interesting
one.
Number 6.
Planet Protectors
Management of a galaxy would be a truly monumental undertaking by an undoubtedly highly advanced
civilization that would possess technologies that might be, by our standards, incomprehensible.
But there are other ways to make a civilization’s home star system safe from any nearby unstable
stars or other such threats, if they set their sights only on that system.
And the ability to do that on the level of a single star system may not be that far in
our own future, at least as far as hypothetical capability is concerned.
The most obvious problem with our own solar system, and very likely many others in the
Milky Way, are the threats posed by asteroids and comets.
Impacts have certainly happened in Earth’s past, and even humanity’s past.
Both Barringer crater in Arizona and the newly discovered 31 kilometer crater buried under
Greenland’s ice hit well within human prehistory, though it’s unlikely either one was actually
witnessed and it’s not certain what effects the Greenland crater in particular might have
had on earth’s climate.
But with proper observation these sorts of collisions can be avoided, and even current
technologies are plausibly able to nudge asteroids around so long as we know they’re coming
well ahead of time.
Seemingly, this would be something alien civilizations would be motivated to tackle as well, if they
too face that kind of threat.
But another threat they might face is that of a supernova, or a gamma ray burst.
While these threats, at least as far as we know, don’t pose too much of a risk to earth,
though there is a chance the destruction of the star WR104 might in the future, civilizations
nearer to the sources of events like that might be in serious danger.
But, threats of this kind might be mitigated by an exocivilization through building an
orbital blast shield to protect their planet.
Accomplishing this would not be dyson sphere level technology, rather it seems more doable
as an orbital shield.
And, other problems, such as stars that increase in luminosity as they age, such as our own
sun, could be addressed by using star shields to control the effects of that, at least for
a time.
Any of these hypothetical solutions should in principle be detectable as technosignatures
in light curves of stars and transiting planets, and any civilization employing these techniques
may not be all that more advanced than we are in that we would probably know what they
were doing if we ever saw this kind of activity.
Number 5.
Planet Migrators
If this technosignature was ever seen, it seems likely that it would come only from
a very discrete civilization that doesn’t really make itself known any other way.
It’s the concept of planetary migration, and such a civilization might live out most
of its existence as an earth like civilization: biological, technologically advanced, but
they otherwise never really leave their star system for lack of any reason to do so, after
all, colonizing a galaxy is an expensive endeavour.
Some may simply choose not to bother.
But such a civilization couldn’t exist indefinitely; star systems like ours are not static things,
instead they are dynamic long term.
And like our own sun, there would come a time where a civilization must mitigate the effects
of their changing star.
One way to do this would be to very slowly migrate their planet to a more suitable orbit
as their star changes, perhaps in conjunction with star shades.
This would be a very long, drawn out process whereby objects, such as large asteroids,
are orchestrated to pass by a planet over the course of potentially millions of years
to slowly tug that planet further from its parent star centimeter by centimeter, as the
star undergoes it’s changes long term.
To spot this kind of activity, we would need to be watching a star system periodically
for millions of years, but after that amount of time of observation, the deliberate migration
of such an observed planet should be readily evident.
4.
Star Ticklers
We often envision alien civilizations as spanning the galaxy, or at least an empire of star
systems within it, expending enormous amounts of energy on starships and communications.
But this may not be how it actually would be, from a practical standpoint.
Instead of building empires, civilizations might simply choose to improve their own star
system and never cross the vast distances of space because it’s simply too expensive
to mess with.
Or they may found a few colonies in nearby star systems and simply stop when they’ve
concluded that they’ve gone far enough with their real estate portfolio.
This pragmatism could extend into other areas, such as sending out SETI signals.
If a civilization really wanted to contact other civilizations cheaply, and easily and
using little energy, one way to do it would be to just mess around with natural sources
of light in such a way as to be identifiable to other scientists in the galaxy as artificial
manipulation.
Examples of this might be to bombard a variable star in such a way as to make it pulsate in
an unnatural way, or timing a communication with an astronomical event, such as a neutron
star merger, that would be anticipated by the rest of the galaxy’s scientists.
Piggybacking a signal when the exocivilization knows that everyone is looking, perhaps a
better option in comparison to expanding the energy needed to continuously transmit a signal.
About all one could say about such a civilization is that they are probably very smart with
their available resources.
Number Three.
Terraformers.
Finding and studying truly Earth-like exoplanets is something that in the coming years promises
to give us an unprecedented insight on habitability within the Milky Way.
Instruments like the James Webb Space Telescope will expand our ability to see and study these
worlds, and future instrumentation even more so.
As a result, we will eventually be able to study habitable worlds in some detail.
What happens if we begin to see patterns in that data.
Say a grouping of habitable worlds is found, where one might find several, or even tens
of habitable worlds clustered together in a group of suitable star systems.
An oasis of habitable worlds in an otherwise sparse section of the galaxy.
This could be due to chance, of course, but it might also indicate a civilization that’s
expanding out of their home star system and actively terraforming suitable worlds in the
systems around them.
It would be difficult to pin this down definitively to terraformers, but over a long period of
time of observation these activities might be detectable as they continue to expand and
other habitable worlds begin appearing.
Or, another possibility would be a habitable planet with an unnaturally thick atmosphere
that it otherwise should be too small to hold onto, similar to a terraformed version of
Mars, where long-term atmospheric loss would have to be managed.
Any civilization capable of doing this would have had to master long-distance space travel,
and would demonstrate very long term thinking and planning.
While they may not be a full on Kardeshev Type III civilization, they would be still
be highly advanced, and given that penchant for long-term thinking, it seems likely they
would be a stable civilization that might last for a very long time indeed.
Number Two.
Von Neumann Bio Printers
Ever since mathematician John von Neumann first envisioned the concept of self-replicating
machines, the potential uses people have thought of for such machines has only increased in
number.
From nanotechnology that can self-replicate, to exploring the galaxy efficiently at sublight
speeds using such probes, it seems, on its face, a natural thing for civilizations to
eventually build.
We see no such thing however when we look to the heavens, since von Neumann probes that
self-replicate without restriction would eventually consume entire galaxies.
We don’t see that happening in the universe.
But that may not mean that such machines do not exist, only that they are governed to
prevent them from getting out of hand.
But it still remains that self-replicating machines are an efficient way to put a probe
in every worthwhile star system in the galaxy.
That said, life also is self-replicating.
That’s biological reproduction, and it is one of the absolute essentials for life.
But biology is limited to the environment it evolved in, and it’s hard to think of
a harsher environment than deep space for life.
Ideas of panspermia within a star system are still on the table, but interstellar panspermia
seems less likely.
A microbe surviving in a rock for tens of years or so while crossing space is one thing,
the same surviving for millions of years across interstellar space is another.
But would an alien civilization be able to one up natural panspermia?
Possibly.
Von Neumann probes could, in principle, be equipped with 3d printers of sorts.
If a probe came across a civilization, or otherwise interesting colonizable world, it
might then be able to print out a copy of a member of the biological species that sent
it.
That member could then make contact, or be tailored to survive in the new planetary environment
by altering its biochemistry if it were a bit different than the conditions of the home
world.
In other words, the founding of colonies in the Milky Way may not be a matter of biological
life travelling at all, rather it may be machines seeding new civilizations by simply printing
them out.
Number One.
Living Machines
This last option for speculating about what an exocivilization might be like, is also
perhaps the most alien.
Biological civilizations may share some very basic features, such as types of biochemistry,
and convergent evolution where a similar outcome might evolve between intelligent species due
to the realities of existince.
You can’t really be a technological species without the ability to understand engineering
and mathematics for example.
But it’s also a distinct possibility that civilizations may eventually forsake biology
entirely, something glimmers of which are appearing within our own civilization.
And there are significant advantages to becoming a machine civilization.
One of these would be the ability to exist effectively anywhere in space where resources
are abundant and energy generation is easily accomplished, and in fact even the cold of
space itself is useful for a machine wishing to calculate efficiently.
But what might a machine civilization be like?
There are many possibilities.
A few of these would be a giant computer built as concentric dyson shells to eek out every
bit of energy possible from a star.
This is usually termed a Matrioshka brain, and would represent unfathomable computing
power by our standards.
Another might be self-aware conscious von Neumann probes, or even shrunken civilizations
making use of nanotechnology and the ability to build small.
In which case, how would you ever detect a tiny exocivilization that doesn’t even need
an entire planet?
You probably couldn’t, and that brings up the point that exocivilizations may simply
be very difficult to detect, and the more advanced they become, the more different they
are.
And the argument can be made that much like a person in the middle ages couldn’t possibly
have predicted what the world of today would be like, we may in turn not be able to predict
what we’re going to look like in a thousand years, much less envision what an advanced
exocivilization perhaps millions of years older than us might look like.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently wondering if exocivilizations
might be more like us than many of us would like.
While it could be a noble universe full of peaceful space faring civilizations, it might
also just as easily be a universe where the latest antics of Gorp the Attractive are streamed
on alien internets along with cute pictures of pets that would be deadly to humans should
we ever try to pet them.
Very troubling indeed and be sure to check out my books at your favorite online book
retailers and subscribe to my channels for regular, in-depth explorations into the interesting,
weird and unknown aspects of this amazing universe in which we live.