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.
