KIC 8462852 And the Likelihood of Finding Alien Civilizations

Over the past few weeks a number of articles have appeared in various news sources about the star KIC 8462852. This was one of the thousands of stars observed by the Kepler telescope in its search for extrasolar planets. For those who are unfamiliar with Kepler and how it works, the telescope observed stars over a long period of time, watching for periodic dips in their brightness that indicated the presence of planets passing in front of the stars and blocking a tiny portion of their light. Kepler’s initial observation period came to an end when two of the reaction wheels used to maintain the stability necessary for precise observations failed, though since then it has been re-purposed for more limited observations. The initial haul of data is still being analyzed and has already resulted in the discovery of hundreds of planets. Some of these planets are super-Earths (planets not much larger than Earth, as opposed to gas giants like Jupiter), and a few are in the theoretical habitable zones around their stars where liquid water could exist on their surfaces, though we as yet have no way of knowing if it actually does.

What stood out about KIC 8462852, a star somewhat larger than the Sun (spectral class F3 as compared to the Sun's G2) that is about 1480 light years away, was that the observed dips in its brightness were too substantial to have been caused by a planet, and they were irregular. In other words, in the two observed dimming events, which came about 750 days apart, the star dimmed, brightened and then dimmed again several times. This is extremely odd, and astronomers have struggled to come up with an explanation that fits the data. This uncertainty led a few astronomers to note that there was an additional possibility that didn’t involve natural phenomena. This was that the star was surrounded by some sort of alien megastructure designed to capture the star’s light for use as an energy source. This sort of construction has been proposed as a theoretical possibility before, with the most complete version being what is known as a Dyson sphere (after Freeman Dyson, who helped popularize the concept), which would totally surround the star in order to capture all or nearly all of its light. This is obviously not what is being observed here, but as Dyson himself later noted that a solid sphere or even ring around a star was "mechanically impossible", so a practical Dyson sphere would have be something like a swarm or bubble of constructs around the star, so the possibility remains open. Furthermore, some have pointed out that the megastructure could be incomplete (whether because it’s still under construction or because it is abandoned and derelict). In any case the idea is that it is something like a "Dyson swarm" that is being seen here.

Most likely, though, the explanation is something far more prosaic. Even the astronomers who have talked about the possibility that what is being seen at KIC 8462852 is an alien artifact have emphasized that the true explanation is likely to be something natural. The leading theories seems to be a unusually large swarm of comets, presumably disturbed by a recent passing star, though some question whether it is possible for a large enough number of comets to account for the data to have been disrupted, or simply dust, though astronomers are not sure why a seemingly older star (KIC 8462852 is thought to be at least as old as the 5-billion-year-old Sun, though there is still some uncertainty about that) would have so much dust around it. Despite the difficulties with both ideas, dust seems to be the most likely cause. Certainly we should want to see a lot more evidence before leaping to the extraordinary conclusion that aliens are the cause, or even anything more than a remote possibility; as Carl Sagan once said, extraordinary claims require extraordinary evidence.

But all the talk about KIC 8462852 does bring up once again the long-running debate over life in the universe, and specifically the likelihood that there are alien civilizations capable of space travel (obviously necessary to build any kind of structures around even the local star) out there somewhere. Of course, there are a lot of uncertainties involved, spelled out most clearly in the famous Drake equation. How many habitable planets are there? How many of those have life? How many planets with life give rise to technological civilizations capable of space travel? How long do such civilizations typically last? Everyone has different answers to these questions, but no one knows for sure. However, I’m willing to give my own take on the matter, even if I can’t claim to be an expert.

From all the planets we have discovered over the past two decades, we can estimate that there are over a hundred billion planets in the Milky Way, which is home to several hundred billion stars, many or even most of which are likely to have planets. Most of these planets will not be at all Earth-like, but it still seems likely that there could be billions in our galaxy that are similar enough to Earth to be considered habitable. The next question is how likely it is that life has arisen on these planets. We’re still not certain exactly how life arose here (though we’re getting closer all the time) and we still haven’t found definitive evidence of life originating anywhere other than Earth. Given how pervasive life is on Earth, though, I would not be surprised if we find traces of it elsewhere in the solar system, such as on Mars, Europa or Enceladus, and the fact that life seems to have appeared fairly early in Earth’s history is also a positive sign for how likely it is to arise in the first place.

But so far we are only talking about life in its most primitive, single-celled form. There is a rather large leap from this to a technological civilization capable of space travel. In fact, even if life in general turns out to be fairly common in the universe, we may find that on the vast majority of planets it consists entirely of single-celled organisms. After all, life existed on Earth for over 3 billion years before multi-cellular life appeared around 600 million years ago. To put that in perspective, life appeared within a billion years of the Earth’s formation and quite soon after the end of the hypothetical Late Heavy Bombardment era, during which it may have been difficult for even primitive life to survive (and even harder for any traces of life that may have arisen to survive for us to find), but for the vast majority of Earth’s history, there were only single-celled organisms – no plants or animals of any sort, much less intelligent life. This may indicate that it takes special conditions that are not easily fulfilled for multicellular life to evolve, and on many planets where life appears, these conditions may never arise.

Even if multicellular organisms appear, there is no guarantee that intelligent life forms will evolve – particularly intelligent life forms capable of constructing spaceships. Multicellular life had been on Earth for over half a billion years before humans evolved, so obviously intelligent life takes some time to appear. Of course on Earth there have been periodic mass extinctions that have wiped out most life, essentially setting back the evolutionary clock, so it isn’t as if we’ve had half a billion years of continuous evolution. On the other hand, other planets are likely to also suffer from periodic mass extinctions, and intelligent life would have to evolve in the periods between such events, which might be difficult if they were more frequent than they are on Earth. And even if intelligent life evolved, it would not necessarily be capable of developing advanced technology. It is often argued that dolphins are highly intelligent, but even if they are as smart as humans, they obviously can’t build spaceships. For that matter, even humans existed for hundreds of thousands of years before developing advanced technology, and we couldn’t have done that without the right raw materials (for instance, sufficient amounts of iron that could be easily mined). Then there is the obvious danger of an advanced civilization destroying itself in a relatively short period of time, just as we could end up destroying ourselves (or at least sending ourselves back to a low level of technology) through nuclear weapons or catastrophic climate change. After all, we've been capable of space travel for only half a century. That's 0.025% of the time modern humans have been around, and 0.000001% of Earth's history. For us to have a chance of encountering (even from a distance) any alien civilizations, some of them would have to last a lot longer than that.

So there probably are a lot of barriers to advanced technological civilizations arising, to the point that they may only appear on a tiny fraction of habitable planets. But on the other hand, if there are 10 billion habitable planets in the galaxy, even a one in a hundred million chance that an advanced civilization had arisen and survived long enough to be around now would mean that there would be a hundred such civilizations. That’s not a particularly huge number, considering how large our galaxy is, and if they are that rare we may have trouble finding them, especially if we keep in mind how huge the distances between stars are - even talking to any aliens living in the KIC 8462852 system would take 3000 years for a single exchange of messages. As for alien civilizations in other galaxies, they would be so far away as to be completely inaccessible even for any form of communication, unless wormholes or other forms of exotic travel turn out to be possible. Still, while it seems too much to hope that KIC 8462852 will turn out to have advanced alien life, it almost certainly does exist somewhere else in the universe, and probably even exists somewhere else in our galaxy. Whether we will ever find it is another matter; however, I am all in favor of continuing to look.