Saturday, August 6, 2016

Aliens, Perhaps, but Not the Aliens of the Gaps

Update (8 August 2016): Audio Interview with Ben Montet.

With the publication of Montet and Simon's arresting new preprint showing even more anomalous dimming behavior by Tabby's Star,  a lot of reasonable people are asking whether it's time to declare this stellar weirdness the work of an ET civilization, or whether it may be soon. While I am emotionally inclined to go this way, and intuitively sense that this may be the ultimate conclusion reached, I am not a believer. There is a fundamental error we still must avoid.


Light curve for KIC 8462852 from Montet and Simon
It is not crazy or deluded to think that this could be the work of ET. Not at all. We know that technological civilizations exist in our galaxy, we just don't know how many. It is easy to get into pointless arguments about whether there is just one, or the universe is swarming with creatures in some ways analogous to dexterous, talking monkeys like ourselves. These arguments are usually based upon probability guesses with very weak, or even non existent empirical support.

The truth is that nobody really knows how common ET civilizations are, or how long they flourish, and the so far null result of our (so far) very poorly funded SETI enterprise isn't much help in resolving it one way or the other, as has been argued by such persons as Jill Tarter for many years now.




So, saying that it could be ET is not the big mistake. The real mistake is closely analogous to an old argument for the existence of God, now largely abandoned by educated theists - called The God of the Gaps argument. In this argument, what we don't know about our origins or how the universe works is attributable to divine intervention - miraculous actions He must take to bring about that which nature can not - as if the nature of His design is somehow deficient. As science closes down the gaps, this god becomes smaller and smaller, and I think you can see why this would be unacceptable to enlightened religious people.

If we can't argue for the existence of God from the gaps in our understanding of human origins, neither can we argue for aliens based upon the gaps in our understanding of astrophysical phenomena. It's really just re-labelling our ignorance as "aliens." No one should be convinced by this.

Does this mean there is no scientific path to detecting ET? Of course not, and the decades of slow and patient SETI research point the way. Simple, but testable models of how an ET civilization would choose to advertise its presence are put forth, and there have been quite a few of these. These make testable predictions of what these beacons would be like and how they can be searched for.

Likewise, much of the focus of research in astrobiology (also with a null result to date) is focused on the question of how will we know extraterrestrial life when we see it? What is clearly different about the observables of a planet (either through a telescope or up close) between one that has life and one that doesn't? This leads to guidance for instrumental, experimental and observational design, going back to Viking lander of the 1970s.

For phenomena like Tabby's Star, we have to do the same hard work, but it is far more complex than SETI. in SETI, we generally assume that ET wants to reach out to other technological life forms, and will pick a method for communicating with us that is least in principle accessible to us. In other words, in SETI we can assume we know what ET is up to  - or were up to, as they may be long gone. For the sort of highly energetic side-effects of ET activity such as a Dyson Swarm, we probably don't know what they are up to, or why.  We may not even have a concept to express it. We will have to guess. These guesses would help us determine where to point our telescopes, what parts of the electromagnetic spectrum to search in, and what specific signatures to search for.

And we will have to be patient, since we will be almost certainly be wrong at first, or perhaps just unlucky in our search. We don't need to nail it exactly, but we will need to develop rough models of ET activity that distinguishes it from nature. These models would more or less fit the data that we think anomalous, would make testable predictions, and would show how to rule out at least known natural phenomena. Such a family of models may be available next year, or it may be in 100 years, but the more anomalous data we have, the more the models can be constrained.  The existence of serendipitously discovered phenomena like Tabby's Star certainly motivates this kind of work, and may even stimulate funding to undertake the search.

When this work is done, and the data is in, maybe we will know with reasonable confidence that ET Civilizations exist not far from us. It is impossible for us here and now in 2016 to see beyond that point. The thought of our children standing on that threshold and looking out into a living universe with newly enlightened eyes is thrilling to me, and I hope I live to see it.