One of the biggest questions about colonizing the galaxy are the sheer distances and energy
consumption involved with doing it.
It’s easy to get pessimistic here, it takes enormous amounts of energy to get to another
star system, even a close one, our current best chance at catching a glimpse close up
of a nearby star system are things like Breakthrough starshot, where very tiny micro spacecraft
are propelled at a small fraction of the speed of light to the nearest star system using
very powerful lasers, and even that would take a number of decades to do that, just
to get some data and perhaps a snapshot of another star system.
But there is another way, and over time, it could provide a much more efficient and effective
way to colonize the galaxy, and indeed, a novel, but perhaps realistic solution to the
Fermi paradox is hidden in here.
In short, this method does not involve a civilization engaging in far interstellar travel, but rather
relying on the stars of their galaxy to do the work for them.
Stars appear to move from our position on a rotating planet orbiting a star, but they
also have motion of their own, called proper motion as they orbit the center of the galaxy,
but also move independently for various reasons.
This leads to a situation where the galaxy is dynamic and star systems pass close by
other star systems routinely, even out here in the suburbs of the galaxy.
This has led to a situation where our sun since its birth has encountered numerous other
stars at distance much closer than the current distance to the nearest star system, proxima
centauri at 4.2 light years away.
An example here is a star that is currently about 22 light years distance, but there was
a time when it was much closer, passing inside our own Oort cloud around 70,000 years ago.
Known as Scholz’s star, this star is actually a system of a red dwarf and a brown dwarf,
and constitute what might be a very ancient star system, possibly as old as ten billion
years old, but that’s been difficult to pin down and may end up being much younger.
The closest approach however was less than a light year away, at abbott .82 light years,
a far shorter distance than from the nearest current star, and so close in fact that while
it passed through the Oort cloud it could be considered to be within the solar system
and very well could have captured material from our oort cloud and took it along with
it, but also may have perturbed material from the Oort cloud and sent it into the inner
solar system, which is set to arrive in about two million years, potentially setting Earth
up for another impact and mass extinction event if we haven’t mitigated the threat
by then.
As an aside, that’s an interesting science fiction scenario to think about.
Say human civilization fails, but we don’t go extinct, rather we return to a primitive
existence and start evolving again.
Some future member of our genus might go extinct in a giant impact caused by Scholz’s star
in the ultimate in sad scenarios where they, or rather their progenitor, us, once knew
of the threat and probably could have done something about it had we not lost civilization.
The dinosaurs, they had an excuse, nothing preceding them could have predicted the asteroid
impact.
The dominant species before the flourishing of the dinosaurs included amphibians the size
of volkswagens, they were probably not interested in astronomy.
But if it happens to some future evolved human, it’s all on us.
That said, had we been more advanced 70,000 years ago, the story of Scholz’s star may
have been very different.
During that close encounter, we were here, anatomically modern humans were already on
the order or more of half the age our species is now.
If they’d have achieved space travel that early, the star system was far more easily
accessible.
They might have colonized it, perhaps finding any rocky planets or moons there, or filled
the system with O’Neill Cylinder habitats and we would be a dual system species by now,
with a 70,000 year old colony that takes 22 years to contact, and a further 22 to hear
back from.
Ironically though, humans during the approach would not have seen Scholz’s star or its
companion.
At it’s brightest and closest approach, it would have shown at magnitude 11.4 in the
Northern Hemisphere sky, far too dim to see, with the lowest magnitude visible to the human
eye on average being about 6.5, but that varies person to person.
But had we telescopes, we definitely would have seen it as a very high proper motion
star indicating a close pass.
To explore and colonize it, they’d have had ample time to do both with time left over,
as the encounter lasted a very long time.
And it wasn’t the only recent stellar encounter, nor will it be the last.
The latest estimates are that the orange dwarf Gliese 710 will pass near the sun about 1.29
million years from now.
This star will pass only .16 light-years away at its closest.
This one is different in that it will be readily visible to observers in the far future, rivaling
the planets in brightness, and will likely exceed the brightness of most stars visible
at that time from earth, and it’s high proper motion will make it’s movement noticeable
over a single current human lifetime.
While no planets have been detected orbiting Gliese 710, it’s possible that it has them.
And being an orange dwarf with a mass only about 57% of the sun, it is actually rather
sun like and belongs to a class of star that is thought to be even better for life than
our star system is, at least as far as stellar classes and longevity go.
And it holds the same potential to perturb the Oort cloud when it passes through sending
a hail of comets this way.
Even if none impact earth, it’s estimated that the encounter will produce about one
naked eye comet per month visible from earth, and will do so for a very long time, and will
increase the net cratering rate of the inner solar system significantly.
Dangers aside, which any effects would again take a large amount of time to happen after
the encounter, if there is a planet or raw materials in the Gliese 710 star system then
we could easily reach it, and colonize it.
While 1.29 million years is a long time to wait, it will afford an easier opportunity
for colonization than a standard trek across light years of space will, and on average
there should be many stellar encounters in between that we are unaware of at this time.
And Gliese 710 is the right kind of star to colonize, offering a very long lifespan as
opposed to the sun.
Once you have two colonies, then the chances for stellar encounters doubles because you
now have two independently moving stars both having encounters of their own.
As more stars are colonized through this method, while slow moving, the end result is a colonization
of a very large part of the Milky Way.
And therein is a potential solution to the Fermi Paradox.
Proactively traveling the galaxy and colonizing it at sub-light speeds is a long, slow process.
It would take several million years at sunlight speeds, and even then you’d need to do it
via self-replication von Neumann style to gain an exponential advantage.
But maybe that isn’t realistic.
It certainly isn’t for us right now, and to actually initiate such a task we will need
centuries, or even longer, with an absolutely massive investment of time, expense and energy.
Maybe the solution to the Fermi paradox is that no one does this.
Rather a better plan perhaps would be to colonize and conserve the solar system you’re native
to, and then send out colonizing ships to passing star systems whenever you get the
chance.
Given that the sun is estimated, on average, to have a star pass through its Oort cloud
about once every hundred thousand years, that’s a lot of opportunities for colonization over
the long term.
Especially considering that the vast majority of stars that make up the milky way are habitable
red and orange dwarfs, just by sitting home numerous colonizable stars will simply deliver
themselves to us.
Presumably, for a very long lived alien civilization, they will see a similar rate of encounters
and take advantage of them.
But given that this process of colonization is inherently slow, it may be that galactic
colonization is invariably a slow process, and either no one has had enough time to extensively
colonized enough passing stars to be easily detectable without knowing exactly where they
would be.
Civilizations then become needles in a haystack, but if you can identify just one technosignature,
it could drive a search for stars near it that may have passed by the initial civilization
and subsequently detect a cluster of technosignatures based on the movements of nearby stars.
In this way, you may even be able to reconstruct which star is the origin point, and which
stars were colonies, and even work out roughly when each colony was founded if you could
determine the motion of their host stars.
Incidentally, there are other potential ways to glean information about such a civilization
based on their technosignatures.
One would be if they are based on a planet, or in space.
Say you receive a radio signal, it may be that the transmitter is located on the surface
of a planet, and will leave characteristic signatures of the planet’s rotation.
Through this, you could determine how long the civilization or colony’s days are.
You could also, over long term observation, determine how far they are in their orbit
around their star, whether the transmitter planet is in the habitable zone of that star,
you could use radial velocity or the transit technique to try to determine the size of
their world and so on.
And, of course, the holy grail would be to decipher their transmissions, though that
will be beyond elusive.
That’s somewhat of a problem in SETI, if you do get a signal, and it’s not some alien’s
radar, but rather communications, how do you decipher what the information is?
The reality is that we may never be able to, especially if the transmission was not meant
for us, but an eavesdropping on their own internal communications, perhaps colony to
colony transmissions.
But the idea of using passing stars for colonization comes with one other implication, a rather
spooky one.
The sun has had many past encounters with stars going back to the formation of the solar
system.
It is conceivable that it happened thousands of times over the last 4.6 billion years.
Given that the Milky Way is far older than the sun, and may have been habitable for billions
of years before Earth formed, and then Earth was simply a microbial and then animal planet,
with homo sapiens and civilization only recently coming into being.
So then the question has to be asked “Why hasn’t anyone colonized this star system?”.
Depending on the situation, that might be an even greater indicator of the great silence
than a lack of any distant technosignatures thus far.
Indeed, the Fermi Paradox is predicated on the notion that we should see evidence of
aliens everywhere, including in our own star system.
But we don’t, at least unambiguously.
But say it’s more subtle, maybe aliens see no need to colonize passing star systems,
maybe they are happy with the planetary system they have and bear no desire to leave it.
Maybe the notion of colonization is a very human thing that we share with very few others.
That aside, an alien civilization may maintain a presence in a passing star system for entirely
different purposes.
Monitoring, perhaps for scientific purposes.
This might lead to our solar system being full of defunct inoperative alien probes put
there by civilizations we’ve passed by.
We may never know those are there.
If a probe the size of a house is sitting somewhere in the solar system completely dead
and eroding in the interplanetary medium, it’s entirely possible that we could never
run across it, even if we colonize the entire solar system.
The solar system is huge in comparison, and with no active emissions from such a probe
it may never be found at all, or found thousands of years in the future, and evidence of alien
life was right under our noses the whole time, we just had no way to know it was there other
than chance.
These types of probes, sometimes termed Benford probes, might also remain active and simply
lurk.
Such a probe would need to be self-repairing, not necessarily self-replicating in the sense
of a von Neumann self-replicating probe.
Rather it simply maintains itself, sitting quietly, perhaps transmitting home every so
often, just monitoring our star system for scientific purposes, or monitoring us for
cultural purposes.
This scenario defeats the distance and time problem of space travel to get to earth.
We often object to the idea because it just doesn’t seem feasible for living aliens
to invest in that.
It’s better for a von Neumann probe, a self-repairing machine doesn’t necessarily care about time
or distance if it can live for millions of years and it’s sole goal is accomplishing
the mission it was set to by its creators.
But in the passing star system scenario, it’s not even that hard.
You just place such probes in every star system you encounter, and you eventually get a decent
sampling of the galaxy from those probes.
If you go a step further and make them capable of self-replication and/or manufacturing using
available raw materials in the star system they are stationed in, that’s where it gets
even spookier.
Once you have a probe of this nature in your star system, you arrive on the one plausible
way that the UAP/UFO phenomenon could be of alien origin, or at least some cases.
After all, if you have something sending, say, atmospheric probes into the atmosphere
of the most interesting exoplanet in our solar system, earth, and someone sees it, then there
it is.
Admittedly, I’m skeptical of this by nature, I need to see solid scientific data, but it
is plausible.
Hopefully, with the Galileo Project having deployed its first instrument package, maybe
we’ll get that data and identify the unidentified, whatever that may be.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently worried that maybe
earth isn’t the planet aliens would colonize if they invaded.
What if they just showed up, displayed no interest in us Rendezvous with Rama style,
and just planted themselves on Oberon and made no attempt at contact.
We’d be like, so, why’d you choose Oberon.
And the only thing we ever hear from the aliens is “meh, Just ‘cause” and then permanent
silence.
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