For decades, one of the most important mysteries facing humanity has been whether or not we’re
alone in the universe.
Space is vast and, so far, empty, but with so many stars and planets floating around
in the galactic ether, the argument goes that one of them must be able to host life as well.
But just how likely is that possibility?
And, how close to us could it really be?
This is Unveiled, and today we’re answering the extraordinary question; are 36 alien civilizations
living in the Milky Way?
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A new study, published in the Astrophysical Journal in June 2020, has re-contextualized
the search for extra-terrestrial life by taking a fresh look at the famous Drake Equation.
The study, led by researchers at the University of Nottingham in the UK, guesstimates the
number of CETI, or “communicating extraterrestrial intelligent” civilizations, that could be
in our galaxy… putting the figure at somewhere between 4 and 211, but most likely a “few
dozen” - or about thirty-six.
So, there’s more than a few things to understand here…
First, the civilizations that the team are proposing would all be able to send radio
signals out into space - much like we can - which is what qualifies them as “communicating”.
Next, and more significantly, however, researchers reached this new number of potential alien
societies by developing a calculation called the “Astrobiological Copernican Limit”…
which is essentially a more specific “alien probability” analysis than the much more
famous Drake Equation.
The Drake Equation, devised by the astrophysicist Frank Drake in 1961, sets out to estimate
the number of potential alien civilizations, too… only it’s infamously broad in its
approach.
The equation looks at seven criteria (none of which we conclusively know the answer to),
including the rate of star creation and the possible lifetime of a communicating civilization.
As a result, because of all the moving parts, the various attempts to “solve” the Drake
Equation have generated wildly different outcomes down the years… alternately suggesting that
there could be anything from zero other civilizations, for example, to tens of millions of them.
The Astrobiological Copernican Limit calculation, however, significantly streamlines and tightens
the method.
Crucially, it works on the assumption that life on Earth develops “scientifically”
rather than at random, and that intelligent life on an alien planet would therefore evolve
in a similar way to how it has done on Earth… that is, it would take roughly five billion
years to get to this point.
It then takes into account the estimated number of planets within the habitable zones of their
respective stars in the Milky Way… and, hey presto - it deems that there’s potentially
between 4 and 211 communicating civilizations in our galaxy, or about 36!
Much like the Drake Equation, though, the Astrobiological Copernican Principle isn’t
without its fair share of problems.
Again, we can’t accurately know the correct figures to input into it… with estimates
on the number of anything in the Milky Way tending to significantly differ, from source
to source.
We simply don’t know the exact number of stars or exoplanets in the galaxy and haven’t
yet even confidently observed an exomoon.
So, while this new method is quicker, neater, more specialised, and arguably more authentic…
it is by no means definitive.
We’re still very much at the stage of “there could be 36 alien civilizations in the Milky
Way, but there also really couldn’t be”.
There’s also the fact that we’re still not absolutely certain what caused intelligent
life to evolve even on Earth itself, so the assumption that it even could happen widely
across the universe under what might be deemed the “right conditions”, is still a vast
- but in this case vital - leap.
The whole “estimating the lifespan of a communicating civilization” thing is really
tricky, too.
We only have ourselves to measure against, and though humans have been on Earth for 200,000
years or so, we’ve only been able to send radio signals for about a century… and we
have no idea how long we’ll survive as a radio-signalling, communicating species.
This means our best guess at how long such a civilization could last has only one, very
modest data point to work from - of at least 100 years.
While this latest method to count unseen aliens isn’t infallible, however, it does prompt
us to think about the search for extraterrestrial life from a range of other perspectives, too…
which is always fun.
Another takeaway from the study, for example, is the calculated probable distance between
us and the next civilization, with it suggested that the closest alien group could still be
17,000 lightyears away.
This means that even if we knew with 100% accuracy that there really was an intelligent,
communicating civilization that distance away from us, well, we’d be waiting some 34,000
years after sending a simple message to get a similarly simple response back.
As for the prospects of conversing with such a society in depth… there aren’t any.
Not only that, but 17,000 years is obviously a long time… and more than enough time for
a civilization (ours or theirs) to disappear for any number of reasons.
Barring some sort of far-future immortality technique, at the very least anyone alive
to blindly send the initial message would be long, long dead before the reply came through.
What’s even more disheartening, though, is that even if there is an alien civilization
out there, or even 36 civilizations or more, how likely is it that they’re sending out
radio signals to try and communicate in the first place?
Arguably, not very.
Humankind has been sending radio messages into space for decades - the most famous of
which being the Arecibo message in 1974 - but it’s not automatic that other species would
do the same thing.
While the Astrobiological Copernican Principle assumes that other life will’ve developed
scientifically and somewhat similarly to ours, it could still be completely and fundamentally
different to us… with zero use or knowledge of our communication methods.
Nevertheless, there has been some cause for belief in recent decades, too, that perhaps
an alien message would be receivable and decipherable for us.
The most famous of all incoming signals was the “Wow!” signal picked up by the Big
Ear radio telescope at Ohio State University in 1977.
When translated, it amounts to a string of six characters, “6EQUJ5”, and has been
variably called the most likely candidate for a true alien communication.
In 2012, we even sent a response to the signal from the Arecibo Observatory… in the form
of 10,000 tweets all tagged with “#ChasingUFOs”.
More recently, notable radio signals from space were picked up by CHIME, the Canadian
Hydrogen Intensity Mapping Experiment, a radio telescope, in 2018.
CHIME detected what are known as FRBs – “Fast Radio Bursts” - coming from another galaxy
500 million lightyears away, repeating at intervals of every sixteen days.
But could it be a sign of alien life?
Or, could these interest-peaking FRBs instead be coming from a young neutron star or an
incredibly bright supernova - as per other theories on what they really are.
Either way, as they’re from outside of the Milky Way, they’re not one of the 36 civilizations
proposed by the Astrobiological Copernican Principle… and even if CHIME’s FRBs are
alien in origin, it’d take us hundreds of millions of years to send a response with
current technology; a significant portion of Earth’s life so far!
If anything, instances like the CHIME signal prove just how immense the task at hand really
is.
With a new calculation, the university of Nottingham team has devised a way to argue
for multiple alien civilizations within the Milky Way… but the Milky Way is just one
average-sized example in amongst billions more galaxies in the observable universe.
So, while we may never be able to talk to distant aliens in our own galaxy or beyond,
the belief that “we’re not alone” isn’t likely to disappear either.
The Astrobiological Copernican Limit is one attempt amongst many to estimate how many
intelligent species are out there… but until we have direct evidence that anything else
exists, it’s impossible to tell how accurate the calculations are.
For now, we have to be content thinking there might be 36 alien civilizations living in
the Milky Way.
What do you think?
Is there anything we missed?
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