Have 36 Alien Civilizations Colonized Our Galaxy?

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00:00The first exoplanet was confirmed in 1992. More than 5,000 others have been catalogued since,

00:07and many in a habitable zone. But the truth is, we know, even if we haven't yet confirmed,

00:13that there are billions of other planets out there, and the likelihood of alien life

00:18is almost certain. So, do you think that they might know about us?

00:25A new study published in the Astrophysical Journal in June 2020 has recontextualized

00:36the search for extraterrestrial life by taking a fresh look at the famous Drake Equation.

00:42The study, led by researchers at the University of Nottingham in the UK, guesstimates the

00:47number of CETI, or Communicating Extraterrestrial Intelligence Civilizations, that could be

00:54in our galaxy, putting the figure at somewhere between 4 and 211, but most likely a few dozen,

01:01or about 36. So, there's more than a few things to understand here. First, the civilizations

01:08that the team are proposing would all be able to send radio signals out into space, much

01:14like we can, which is what qualifies them as communicating. Next, and more significantly

01:20however, researchers reached this new number of potential alien societies by developing

01:26a calculation called the Astrobiological Copernican Limit, which is essentially a more specific

01:33alien probability analysis than the much more famous Drake Equation. The Drake Equation,

01:39devised by the astrophysicist Frank Drake in 1961, sets out to estimate the number of

01:46potential alien civilizations too, only it's infamously broad in its approach. The equation

01:52looks at seven criteria, none of which we conclusively know the answer to, including

01:58the rate of star creation and the possible lifetime of a communicating civilization.

02:04As a result, because of all the moving parts, the various attempts to solve the Drake Equation

02:10have generated wildly different outcomes down the years, alternately suggesting that there

02:15could be anything from zero other civilizations, for example, to tens of millions of them.

02:21The Astrobiological Copernican Limit calculation, however, significantly streamlines and tightens

02:27the method. Crucially, it works on the assumption that life on Earth develops scientifically

02:33rather than at random, and that intelligent life on an alien planet would therefore evolve

02:38in a similar way to how it has done on Earth. That is, it would take roughly five billion

02:44years to get to this point. It then takes into account the estimate number of planets

02:49within the habitable zones of their respective stars, in the Milky Way, and hey presto, it

02:56deems that there's potentially between four and two hundred and eleven communicating civilizations

03:02in our galaxy, or about thirty-six.

03:05Much like the Drake Equation, though, the Astrobiological Copernican Principle isn't

03:11without its fair share of problems. Again, we can't accurately know the correct figures

03:16to input into it, with estimates on the number of anything in the Milky Way tending to significantly

03:22differ from source to source. We simply don't know the exact number of stars, or exoplanets

03:29in the galaxy, and haven't yet even confidently observed an exomoon. So, while this new method

03:35is quicker, neater, more specialised, and arguably more authentic, it is by no means

03:42definitive. We're still very much at the stage of, there could be thirty-six alien

03:47civilizations in the Milky Way, but there also really couldn't be. There's also

03:52the fact that we're still not absolutely certain what caused intelligent life to evolve

03:57even on Earth itself, so the assumption that it even could happen, widely across the universe,

04:04under what might be deemed the right conditions, is still a vast, but in this case vital, leap.

04:10The whole estimating the lifespan of a communicating civilization thing is really tricky to do.

04:16We only have ourselves to measure against, and though humans have been on Earth for 200,000

04:22years or so, we've only been able to send radio signals for about a century. And we

04:27have no idea how long we'll survive as a radio-signalling, communicating species.

04:33This means our best guess at how long such a civilization could last has only one very

04:39modest data point to work from, of at least 100 years.

04:44While this latest method to count unseen aliens isn't infallible, however, it does prompt

04:50us to think about the search for extraterrestrial life from a range of other perspectives too,

04:56which is always fun. Another takeaway from this study, for example, is the calculated

05:02probable distance between us and the next civilization, with it suggesting that the

05:06closest alien group could be 17,000 light years away. This means that even if we knew,

05:13with 100% accuracy, that there really was an intelligent, communicating civilization

05:18that distance away from us, well, we'd be waiting some 34,000 years after sending a

05:24simple message to get a similarly simple response back. As for the prospects of conversing

05:30with such a society in depth, there aren't any.

05:33Not only that, but 17,000 years is obviously a long time, and more than enough time for

05:40a civilization – ours or theirs – to disappear for any number of reasons. Barring some sort

05:46of far-future immortality technique, at the very least anyone alive to blindly send the

05:52initial message would be long, long dead before the reply came through. What's even

05:57more disheartening, though, is that even if there is an alien civilization out there,

06:02or even 36 civilizations or more, how likely is it that they're sending out radio signals

06:08to try and communicate in the first place? Arguably, not very. Humankind has been sending

06:13radio messages into space for decades, the most famous of which being the Arecibo message

06:19in 1974, but it's not automatic that other species would do the same thing. While the

06:25astrobiological Copernican principle assumes that other life will have developed scientifically

06:30and somewhat similarly to ours, it could still be completely and fundamentally different

06:36to us, with zero use or knowledge of our communication methods. Nevertheless, there has been some

06:43cause for belief in recent decades, too, that perhaps an alien message would be receivable

06:49and decipherable for us. The most famous of all incoming signals was the WOW signal picked

06:55up by the Big Ear radio telescope at Ohio State University in 1977. When translated,

07:02it amounts to a string of six characters – 6EQUJ5 – and has been variably called the most

07:09likely candidate for a true alien communication. In 2012, we even sent a response to the signal

07:17from the Arecibo Observatory, in the form of 10,000 tweets all tagged with hashtag Chasing

07:24UFOs.

07:25More recently, notable radio signals from space were picked up by CHIME, the Canadian

07:31Hydrogen Intensity Mapping Experiment, a radio telescope, in 2018. CHIME detected what are

07:38known as FRBs – Fast Radio Bursts – coming from another galaxy 500 million light-years

07:45away, repeating at intervals of every 16 days. But could it be a sign of alien life, or could

07:52these interest-piquing FRBs instead be coming from a young neutron star or an incredibly

07:58bright supernova, as per other theories on what they really are? Either way, as they're

08:04from outside the Milky Way, they're not one of the 36 civilisations proposed by the

08:10Astrobiological Copernican Principle, and if CHIME's FRBs are alien in origin, it'd

08:16take us hundreds of millions of years to send a response with current technology – a significant

08:22portion of Earth's life so far.

08:25If anything, instances like the CHIME signal prove just how immense the task at hand really

08:30is. With a new calculation, the University of Nottingham team has devised a way to argue

08:36for multiple alien civilisations within the Milky Way. But the Milky Way is just one average-sized

08:42example in amongst billions more galaxies in the observable universe. So, while we may

08:48never be able to talk to distant aliens in our own galaxy or beyond, the belief that

08:53we're not alone isn't likely to disappear either. The Astrobiological Copernican Limit

08:59is one attempt amongst many to estimate how many intelligent species are out there, but

09:05until we have direct evidence that anything else exists, it's impossible to tell how

09:11accurate the calculations are. For now, we have to be content thinking that there might

09:16be 36 alien civilisations living in the Milky Way.

09:29What do you think? Is there anything we missed? Let us know in the comments, check out these

09:36other clips from Unveiled, and make sure you subscribe and ring the bell for our latest

09:42content.

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