“Are we alone in the universe?” is one of the oldest and most universal questions;
a question, which is not unique to just humanity, that attempts to uncover the captivating yet
daunting realisation that humanity may not be the only presence of life in the universe.
It has become ubiquitous across science fiction and film for generations and for good reason.
This question is fundamentally encapsulated within what is known as the Fermi paradox,
the apparent contradiction between the sheer size and age of the universe and the apparent
absence of any other technologically advanced civilisations besides ourselves.
Or in other words, where are all the aliens?
It the clash between two almost incomprehensible numbers: the age of the universe, that is,
nearly fourteen billion years old and the overwhelming abundance of potential sites
for life, with our Galaxy containing upwards of 400 billion stars alone.
Given these numbers, the odds strongly suggest that the Galaxy should be teeming with life
by now.
In fact, our Galaxy should have been colonised thousands of times over by now and yet, we
see nothing.
No visits.
No broadcasts.
No galactic empire as far as we can tell.
It is from the understanding of ourselves that we can expect any extraterrestrial life
to have a natural tendency to expand into every available space and colonise out into
the Galaxy, especially given that they’ve climbed the evolutionary ladder as far as
gaining intelligence in the first place.
It is the assumption and expectation that other advanced civilisations would do this
that forms the paradox.
However, if you don’t believe that humanity are headed this way, there is no real paradox.
If we won’t even venture outside of our own solar system, then why should we expect
it of other advanced civilisations?
If other advanced civilisations don’t seek to populate other worlds, there’s no reason
why we would notice them even if there were a billion of them dotted across the entire
Galaxy.
And remember, all it takes is one civilisation.
One expansionist, technologically advanced civilisation—not much more advanced than
our own—should be able to colonise the Galaxy within a few million years, which is nothing
more than a mere blink of an eye in cosmic terms.
Indeed, this is the direction that humanity seems to be headed which is hardly surprising;
exploration is quite literally in our DNA.
Our ancestors were filled with the curiosity and evolutionary drive for exploration.
We would not be where we are today if our hunter-gatherer predecessors had decided not
to explore and depart from the savannahs of Africa.
Humanity as a galaxy-spanning empire in two million years from now would view their terrestrial
origin and emergence into the stars as we currently view the emergence and migration
of archaic humans out of Africa, approximately two million years ago.
It does seem to be the next natural step in our evolutionary path.
If colonisation seems to us to be an obvious and inevitable next step, why is it then that
the Galaxy doesn’t appear to be populated at all?
Surely, given the age of the universe and the size of the galaxy, some other advanced
civilisation has had the same idea.
The solutions to the Fermi paradox can be categorised into one of three classes.
First, there are solutions based around the assumption that in some way or another extraterrestrials
are here or have been here in the past.
Second, there are solutions that suppose that other advanced civilisations exist—perhaps
even in abundance—but for some reason or another we’ve not seen or heard from them.
And third, there are solutions that posit we are indeed alone in the universe, or at
least in the Galaxy, and there is a reason, or more likely to be several reasons, why
that is the case.
The number of solutions that can be thought of for the Fermi paradox are, in every sense,
limitless.
There are so many factors involved in finding a solution to the paradox, ranging from a
technological and practical sense to sociological speculations about the psychology of extraterrestrial
civilisations.
Often these speculations—due to the severe lack of evidence and data to go on—reveal
the individual psychology of the person making the speculations rather than reaching any
definitive answer.
That is the problem with discussions of the Fermi paradox but it is, after all, what makes
it so interesting.
And there is a real difficulty with finding ‘the solution’ to the paradox as it must
be applicable to absolutely every advanced civilisation that has ever arisen—which
is why it seems far more likely that if there is an answer, then it will come down to a
combination of reasons rather than just one.
Now today, I wanted to discuss the second category; solutions that argue that “they”
exist but there are reasons why we have observed no evidence of their existence as of yet.
In particular, all the reasons that boil down to the hard and irrefutable fact that space
is simply too vast to conquer.
I do also plan on doing another episode on the third category (that we are indeed alone
in the Galaxy) sometime soon.
Let’s assume that other technologically advanced civilisations are indeed out there—in
fact, for the sake of argument, let’s say there are hundreds, perhaps even thousands
of them distributed evenly across the entire Galaxy at this very moment.
Ever since we’ve been able to, ever since we’ve had the technology to do so, we’ve
had our radio telescopes and the rest of our instruments pointed towards the stars, searching
for evidence of any advanced civilisations.
But for whatever reason, we haven’t seen or heard from any at all, today we want to
answer: why is that?
One of the simplest resolutions that we can muster is that the distance between stars
is too great to permit interstellar travel.
As Douglas Adams famously said, “Space is big.
Really big.
You just won’t believe how vastly, hugely, mindbogglingly big it is.”
Unfortunately for the infant inside all of us, traversing the vast stretch of space between
the stars isn’t as easy as sci-fi makes it out to be.
While from afar the Milky Way appears to be densely packed with stars, the majority of
what we see is empty space.
But it is this empty space between the stars which is what causes us problems and prohibits
not only the feasibility of interstellar travel but also of interstellar communication.
It may be that no matter how advanced a civilisation becomes, it can’t master the art of covering
interstellar distances in reasonable times, which may be the explanation we’re looking
for as to why we aren’t seeing any galaxy-spanning civilisations.
Interstellar travel is not inherently forbidden by the laws of physics in any way, shape or
form but they definitely don’t make it easy for us.
Take for instance, one of the fastest man-made vehicles ever constructed: the Voyager 1 probe.
As it left the Solar System, Voyager 1 had a whopping speed relative to the Sun of 38,000
mph.
At this speed, we would reach the nearest star system, the Alpha Centauri system, at
4.3 light years away, in about 80,000 years.
The fastest human-rated vehicle, Apollo 10, would take 120,000 years to cover the same
distance.
Interstellar travel is definitely achievable with our current level of technology; there
isn’t much difficulty in building a vessel that can leave a star system and head in one
direction for a prolonged period of time.
The difficulty lies however in the time you’re willing to spend on that journey.
Unless you achieve relativistic speeds, the transit times are tough.
And unless a crew as well as thousands of their descendants are willing to endure those
transit times, we are trapped in our own little pocket of the universe.
Is this same for all advanced civilisations?
Is our Galaxy just littered with the remains of single-planet colonisations who were forever
confined to the bounds of their star systems, no matter how advanced they became?
Well yes, that seems to be the case.
Unless, and this is a big unless.
Unless new technologies can be developed that allow us to achieve speeds as great as, say,
10% the speed of light.
This may include interstellar travel powered by nuclear fusion engines, laser propulsion,
solar sails, Faster Than Light travel, antimatter drives or perhaps technologies that we have
yet to encounter.
These speculations solely rely on how advanced a civilisation is and can become.
We don’t have much of a clue on what the limits of technology are.
For all we know, we could be nearing the point at which you can no longer advance science
and technology, however that seems incredibly unlikely for obvious reasons.
It is more likely we are nowhere near the limit, particularly if you look back in history
at how far we’ve come in so little time.
But if humanity still has a long road ahead of us in terms of technological advancement,
why is it then that it appears that no other civilisations have gone further down the road
than we have?
There have been billions of years for one other civilisation to emerge as we have and
take on the feat of interstellar travel.
Perhaps our expectations are too high.
Instead of a Type III civilisation, perhaps it is a Type II civilisation we should be
looking out for, yet we see none of them either.
A Type II culture would be fairly obvious if their star system was in range of our telescopes
as megastructures such as Dyson spheres, Dyson swarms and the like would not only decrease
some of the star’s expected luminosity but it would produce a region of high infrared
emission.
We haven’t spotted any anomalies such as these but that doesn’t immediately conclude
that no other advanced civilisations are in the solar neighbourhood.
There are a variety of reasons why a civilisation would choose to avoid our stellar region and
hide themselves from us; one that is advanced enough can certainly do so without having
to think much of it.
With that being said, it is not just our stellar neighbourhood that we must consider.
The Fermi paradox’s region of interest doesn’t end there nor does it cease at the edge of
the Milky Way.
It should involve our neighbouring galaxies as well (i.e.
The Local Group) as galaxies outside of the Local Group are most certainly out of reach,
even for the most advanced of civilisations.
A Type III civilisation situated in another galaxy would be so blatantly obvious that
you’d barely be able to miss the telltales of one.
Studies of galactic mid-infrared emissions have concluded however that Type-III civilisations
are either incredibly rare or do not exist as far as we can tell for our pocket of the
universe.
If all advanced civilisations do indeed deem interstellar travel too time-consuming to
be practical, then we have our solution, were it not for one little detail.
While it offers an explanation as to why we aren’t seeing the Galaxy swarming with life,
it doesn’t explain the Great Silence (i.e. the absence of extraterrestrial signals).
If it’s a given that interstellar distances are a route that no one’s willing to take,
then extraterrestrial civilisations don’t have much reason to hide and not communicate.
After all, they have nothing to fear in broadcasting their presence to the universe if they conclude
that no potentially malevolent civilisation can come to invade their home planet and colonies.
One can imagine that an advanced civilisation may signal for our help on an imminent threat
to them; they may want to trade with us; they might simply want to announce their existence
and end their seemingly eternal loneliness; there are a great number of reasons why they
would wish to communicate with us.
Why then have we received no broadcasts or, at the very least, detected some of this galactic
chatter between other civilisations?
A reasonable assumption is that transmitting and receiving signals is no easy task.
One could liken it to the most impossible darts shot, except you don’t know where
the dartboard is and you can’t be sure that the dart will even reach.
Although even this analogy does not begin to express the improbability of detecting
a signal from an advanced civilisation that must be pointed directly at not only Earth
but a receiver on Earth at the right time and at the right frequency.
The trillions of possible combinations with these variables make lottery odds seem worthwhile.
Perhaps humanity should just leave the broadcasting to more technologically advanced civilisations.
With that being said, we have been unintentionally leaking signals into space—mostly in the
form of high frequency radio, radar and television—for the best part of a century.
Again, whether or not an advanced civilisation could detect our leakage radiation comes down
to how technologically advanced they are.
In any case, it seems unlikely.
The nature of our transmitters—having a high bandwidth coupled with a relatively low
power output—means that even an Arecibo-sized telescope situated in the outer reaches of
our Solar System would have difficulty in detecting our broadcasts.
The further the signal travels in space, the weaker it becomes and the harder it is to
discern from background noise.
Our leakage radiation has in principle reached an audience of several thousand star systems
by now, having travelled about 100 light years in every direction.
Of course, there is always the possibility that extraterrestrial civilisations don’t
know where to look.
If we were in their shoes (or the alien equivalent), would we recognise Earth as having a high
probability for life?
I don’t think it is too egotistical of us to assume that they would and I don’t think
it is either to assume that they would point their telescopes in our direction at least
every now and then.
This raises questions about how effective our searching methods are for habitable planets.
It may be too anthropocentric of us to assume that life can only emerge on Earth-like planets.
Indeed, with the help of science fiction, we are no stranger to the concept of alternative
biochemistries and environments, having given us the idea of silicon-based life-forms, using
alternative solvents as opposed to water and so on.
Quite frankly, it’s hardly surprising we haven’t eavesdropped on any galactic radio
chatter.
Our efforts have continued now for a little over a century which may seem like a lot of
time in a human lifetime but for the universe, it barely constitutes for a nanosecond of
its time.
The fact that we haven’t picked up on any signals in the small amount of time that we
have been listening is hardly paradoxical.
Perhaps we simply have to be patient.
But that kind of undermines what the paradox is getting at.
The crux of the Fermi paradox is the fact that we haven’t been visited by extraterrestrials
despite there being billions of years for them to do so.
We shouldn’t have to wait for them.
They should already be here, given the time they’ve had.
I think, overall, this solution (that distances between stars are too vast to permit interstellar
travel and interstellar communication) does offer some pretty solid explanations as to
why we aren’t seeing the Galaxy swarming with life.
If, however, you are, like me, fairly optimistic about the limits of science and technology
for any one technologically advanced civilisation, this solution may not be all that appealing.
I, for one, find it incredibly unlikely that we would be the first advanced civilisation
to master the ways of interstellar travel in the entire Galaxy.
For me, the vastness of space between the stars alone does not fully satisfy the Fermi
paradox.
Comment down below your thoughts on this solution to the Fermi paradox.
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If you enjoyed this video check out my most recent video on the development of an interplanetary
transport system, a previous video or perhaps my playlist on the Fermi paradox.
Thank you so much for watching, have a nice day.