Villarroel, Imaz, and Bergstedt 2016 had an interesting theory that they actually tested. Regardless of your opinion of the theory, you have to respect them for actually performing their search, which is something that too few SETI papers do.
They wanted to look and see if any objects have disappeared from the sky and slipped under the radar. The methodology was pretty straightforward: they looked at the US Naval Observatory sky catalog and found objects with low proper motions. Then they created four parent catalogs (with differing criteria like “needs >4 detections” or “needs to be < 18 mag”). They look for and exclude corresponding objects (by position) in SDSS data, which cuts out a lot of their objects. Many of the remaining objects actually are still present in the SDSS data but were just missed by the pipeline – they looked at these images by eye for this reason. Examining by eye also allowed the removal of any artifacts that were causing the difference in detection. After this cut, 148 objects remained. Many of those don’t even have a visible object in the USNO catalog, suggesting that there were errors in their proper motions / positions or were just noise from the beginning. After all of this, only a single candidate remains, shown below.
I personally am not convinced about the existence of this object in the first place. I believe that the authors are talking about the spot in the middle of the “triangle” of objects almost directly in the center of the image… but honestly, I could easily see it just being noise. I don’t know that I would suggest that it was “clearly seen”.
So, now that I’ve gone through the paper itself, why did the authors think that looking for a disappearing object would be an interesting or sensible thing to do, and why might it relate to SETI? The building of a Dyson sphere was suggested as a way to make a star disappear, but I don’t believe that the authors’ timescale (60-70 years) is feasible by even Dyson’s original calculation based on the energy needed to construct it vs. the energy output of the central star. Mostly, a disappearing star or galaxy would be something that we would not expect nature to do, so it’s either interesting SETI or interesting astrophysics (high risk, high reward, high turns-all-of-astro-on-its-head factor). If the action causing the “nature-plus” effect is ETI but not intentional communication, then the philosophy behind this search is the equivalent of searching for the most “obviously artificial” technosignatures possible, which is one way to approach the haystack.
Personally, I like the idea of this search, following Paul Davies suggestion in his lunar artifacts paper – it’s quite simple to make sure no objects have disappeared from the sky in the last few decades. Like, they probably haven’t, but it’s a good thing to check on.
Final Point: The discovery of a disappearing galaxy would be terrifying, whether ETI or not. I honestly don’t know how I would react to that. Probably with the same or greater instinctual fear as I would have towards beings who think it’s fun to send messages in gravitational waves. Maybe some curiosity, but curiosity requires a hope of understanding. A disappearing galaxy would require power/energy so far beyond our comprehension that the result is basically god-like (one is reminded of Q from Star Trek, although he mostly just spent his time trolling Picard, so perhaps that’s a bad example). At any rate, I’m kind of glad that they didn’t find any of those.
The primary conceit of the paper is that, as vegetation produces a reflective spectral “red edge”, artificial materials could produce similar reflective spectral signatures. These signatures, described in the paper as a distinctive change in reflectivity over a narrow bandwidth, could be detectable if they covered enough of an exoplanet’s surface.
A figure from the paper showing the vegetation red edge and the other edges from different artificial materials
The authors find that silicon produces one of these “artificial edges” in the ultraviolet. Even 10% coverage by silicon could be detectable in certain circumstances (tidally-locked planets around M-dwarfs) with next generation telescopes like WFIRST and JWST. Given an assumption about the composition and reflectivity of the material, you can easily get the coverage fraction. From that fraction, you can guess their power usage (this is assuming that the silicon signature is produced by large-scale photovoltaic arrays).
If you think this is a lot of solar panels, check out one of Lingam and Loeb’s planets
The element I most appreciated in this paper was the authors’ clear statement of assumptions and acknowledgements of alternatives and difficulties in their methods. They make it clear that their calculations are predicated on the idea that the civilization is getting their power supply from their host star, not from geothermal energy or nuclear fusion (which they state would cause other signatures, but they don’t try to predict them in this paper). They add caveats that would affect the signature’s detectability from Earth: hazy atmosphere on the planet, strong winds, and cloud cover. They give solid reasons for choosing silicon as the element to focus on in the paper, based on nucleosynthetic abundance, but also show some spectral signatures of other plausible bases for solar panels. Finally, they considered false positives that could also cause a similar signature, in particular a natural material called enstatite*, and ways to differentiate the two (eg. looking for energy redistribution on the surface of the planet from dayside to nightside).
All in all, I found this to be a very convincing and self-aware paper, and I’m very excited to see an artifact-search like this be conducted in the next decade or so!
* Some facts about enstatite (because part of me always wanted to be a geologist)! It’s a common mineral found in igneous and metamorphic rocks and is a 5-6 on the Mohs scale. It’s essential in some Earth mantle materials and is commonly found in asteroids. It has, in fact, been found in crystalline form in some planetary nebulae.
When enstatite is gem-quality, it’s apparently called “chrome-enstatite” and looks like this (thanks Wikipedia).
Settlement: “a process by which an intelligent species spreads to new areas”*
I have a pet peeve about concreteness. I have been to a few conferences now, and an overarching theme I’ve noticed is that someone will have a fascinating concept, but be kind of dodgy when asked about how to directly apply their concept to real methodology.
As an example, the idea of “ecoscenography” was proposed at an art + science + education conference I attended a few years back. The thesis is that theatrical performances can be extremely wasteful – sets are constructed, used once, and then discarded, and the entire process is disproportionately and unnecessarily harmful to the environment. I was involved in theatre for a long time, and was really interested, so I talked to the speaker about implementation (Reusing simple set elements by repainting? Using more recycled materials? A sharing program between schools for costumes/props/set pieces?), and they kept insisting that we should keep it broad, it’s more of a philosophy, and not define any specific techniques. Well, to be frank, that sounds like a great way for your idea never to be of any use to anyone.
A more “concrete” illustration of the power of ecoscenography
I bring this up because I wanted to clarify a point brought up in Taxonomy and Jargon in SETI as an Interdisciplinary Field of Study (the white paper that I presented at DAI 2018). Some of my peers, in telling them about my presentation, argued that one of the less useful-sounding and more pedantic arguments in that talk was the distinction between “colonization” and “settlement”. Here are three arguments I ran into:
We shouldn’t worry about offending / being politically correct to a species we haven’t met yet, that we may never discover the existence of!
Putting a nice skin on the idea of “colonization” by calling it “settlement” is a little bit offensive in a way – it delegitimizes and hides the ugly parts of the analogous historical situations
It doesn’t matter at all to the actual science of SETI and seems like a quibble over synonyms
Here’s my response to those arguments, after a few weeks of on and off pondering. This is not a paper about political correctness, either in its favour or against it. This is a paper that argues that the lack of precise and accurate terminology hinders the logistical workings of and the intellectual vibrancy/creativity of SETI more than in other fields, and we should recognize and take steps to fix that.
If I were as general as the talks that I berated for lack of concreteness in the earlier part of this post, I would leave it at that. But because I’m not, I want to take on this particular example.
“a process by which a central system of power dominates the surrounding land and its components”
Comes from the Latin colere meaning “to inhabit”
Britain would consider new land as terra nullius (empty land) due to the absence of European farming techniques (regardless of the presence of other populations)
conflict between colonizers and local/native peoples
motivations being trade or “shorter-term exploitation of economic opportunities”
“absorbing and assimilating foreign people into the culture of the imperial country”
In science fiction, “sometimes more benign” – word is used very often
Here are some questions that this article brings up, for me (and, in parentheses, some search implications of each broken assumption):
Habitable worlds ripe for the picking… or not?
Why should we assume that an alien race would want to colonize in the first place? (searching for clusters of systems that have similar signatures becomes a poor search strategy)
What if ETI is NOT spreading for the purpose of resource acquisition and energy demand? (maybe black hole energy-farming is a bad thing to look for, shouldn’t look in places that humans would think are valuable (ex. asteroid belts), could be some underlying pattern in the spread based on religious/cultural/societal reasons behind it))
What if the ETI is conscious of their environment and co-exists with the surrounding land? (no technosignatures would appear during the spread)
What if the ETI is peaceful and co-exists with the inhabitants? (multiple different kinds of biosignatures or technosignatures could co-exist in a single area / N could be higher than one would calculate assuming “domination”)
What if the ETI puts von Neumann probes in systems for scientific or other purposes, but does not actually biologically inhabit it? (we shouldn’t just look at biologically-friendly environments like FGK stars)
What if a certain ETI has a very different idea of terra nullius? What if the presence of microbial life will limit the spread of an ETI because, to them, those environments are “already taken”? (we should look for technosignatures where there are no simple biosignatures already)
What if an ETI is a perfect, Sagan-esque archetype and lifts lesser species out of poverty/technological-infancy instead of causing conflict? (look for geographically-grouped, expanding technosignatures, rates of technological development become geographically dependent)
Is our acceptance of the more general, less problematic interpretation of “colonization” in SETI derived from our science fiction instead of our science? (we stick to a term that doesn’t make lexical sense based on stubbornness and end up making some of the other assumptions in this list)
The point of these questions isn’t that any particular suggestion I made is a good idea. A lot of them are not, or violate other fallacies (like the monocultural fallacy, for example). But it’s obvious that if we look closely at the relatively straightforward logical steps that follow from the dictionary definition of “colonization”, all sorts of SETI search strategies end up being implicitly excluded or assumed. Are we self-aware enough to say “well, I know what the word implies, but I wouldn’t let that affect my science in such obvious, drastic ways” and succeed in that quest? I don’t know about anyone else, but I don’t think I’m self-aware enough for that. I’m sure there are some assumptions hidden in here that I’ve missed. I am, after all, only human!
So in your next publication, dear reader, please use the word “settlement” instead of “colonization”. Your science will thank you.
To add an additional complication at the end of this blog post: I discovered that in biology, colonisation or colonization means “a process by which a species spreads to new areas”. This definition has the perfect lack of connotations that we’re looking for in SETI, and would be a strong argument to continue using the word. My response: SETI is a subset of astrobiology, so we will be interacting with people who DO use this definition. Most practitioners, however, will still have the historical connotations in their head (because that’s what we’ve been exposed to, socially, and humans aren’t very good at putting that sort of conditioning out of our heads). To get around this confusion, in SETI, we should take “settlement” to have the definition I posit at the top of the page.
To follow up on the end of my last post, what if by optimizing for photon communication, we’re just making a giant planet-sized wheat triangle that’s primitive, quaint, and functionally useless because no ETI in their right mind uses wheat triangles anymore?
To skip to the punchline, Hippke finds that everything that we know of so far is inferior to photon transmission (specifically 1 nm X-rays, based on the argument in his previous paper), except perhaps physical artifacts (which might be preferable if you don’t care about speed). This is exciting, and puts my mind at ease about the wheat field thing.
He looks at the following methods, and generally finds the following flaws:
You will notice a lot of ???s in the Pros categories, and I think that’s interesting. Hippke does a good job of going through a lot of messaging options that seem ridiculous at face-value (and not excluding them for that), working out some actual physics behind them, and doesn’t jump onto being a proponent of any “new thing!”. I appreciate this.
The assumptions that he makes with regards to point-to-point communication are interesting. He assumes that more information transmitted is preferable to less, information arriving earlier is preferable to later, and more efficiency is preferable to less. He then discusses, at the very end of the paper, how the landscape would change if any of these assumptions were incorrect (which is very cool!), or incorrect and stacking.
I would like to point out that Hart’s sociological argument probably stops any of this assumption-fiddling from mattering too much. Just because one ETI actually doesn’t care how fast information arrives (Because they’re very long-lived? Because they’re post-biological?) doesn’t mean that another won’t. Just because one ETI is naturally incurious and doesn’t care about actually transmitting their entire “encyclopedia” (if you will), doesn’t mean that another is.
If anything, I think that the “more efficiency / less efficiency” might be the easiest one to break without running afoul of this sociological argument. If you have access to enough energy, you won’t care whether a big METI project takes 10^-100 or 10^-95 of your energy budget. And, with the assumption that virtually all ETIs should have been around for far longer than we are (and that they care about energy/resources in the first place!), they’ll all probably have a much larger energy budget, and might not care too much about efficiency. Just a thought!
This paper contains an argument for X-ray SETI. I will admit that I was skeptical when I read the abstract – after all, X-ray photons are much higher energy than radio photons and thus the typical logic of energy efficiency (of the transmitter) does not apply.
The paper speaks about the “streetlight effect” – an observational bias that causes you to “look where the light is good” aka. to search where it’s easiest (cheapest, already available data, good quality data given your technology, etc. etc. etc.). So, to try to preempt the gradual growing of our “streetlight” and cut to the chase, so to speak, the authors wanted to derive a physical optimum instead of just looking at the current technological “sweet spot”.
The Streetlight Effect in comic form
In this paper, the authors only considered photons, which is a choice that I’ll comment on at the end of this post.
They decide that a minimum wavelength for communication is probably about an atomic width; they adopt 1 nm as their order of magnitude value. The choice of this wavelength is dictated by how smooth we could possibly make a physical receiver surface.
The actual focusing of wavelengths of this scale is typically done with X-ray grazing mirrors that involve multiple mirrors in the design, but they are expensive to build. Because of this, the authors also discuss as-of-yet unknown alloys that could be used in a single mirror design and focusing with EM fields (not possible now, needs too much energy, but maybe in the future?).
The authors make the point that the advantage of X-rays is the amount of data that you can send and the tightness of the beam that you can create (both functions of the shorter wavelength). With a tighter beam, the pointings that you choose have to be proportionally more precise, even down to having to account for a planet’s position around a star.
Another benefit of the 1 nm wavelength choice is that it works at all distances, even when extinction is considered. Gamma rays are even better in this regard (they are barely extinct by anything), but they also would require instrument precisions that exceed the physical limitations described in the early part of the paper.
Finally, if you assume that each photon carries 1 bit of information, the authors find that you can get reasonable data rates in the megabit per second-year range, which would be sufficient for substantial communications. They propose searching for intentional communications in the existing Newton-XMM X-ray data. They note, however, that we have the technology to create pulses that are orders of magnitude shorter than we can detect with current technology, and that the time domain constraint might make us miss potential signals.
A Few Final Thoughts
“Ephemerides sharing is likely to be a small but significant component of all interstellar communications” – how best to share ephemerides in a general way, with the least assumptions possible (Schelling Points?) might be an interesting topic in CETI.
Choosing to look at only photons is a fair choice, but I can’t help but wonder if this is analogous to placing a physical constraint on the giant wheat triangle proposed by Gauss by setting it at an Earth diameter. It’s a physical limit for the method, but it means nothing if the method itself is (in hindsight) quaint/silly/outdated. Maybe photons will be a quaint/silly/outdated mode three centuries from now, and this is just a pointless thought experiment. I have a little bit more faith in EM communication than that, but it is something to consider.
Depending on how you count it, this is either my first conference attendance or my fourth. Either way, it’s the first one at which I had a place as a speaker, allotted the same amount of time as some of the biggest names in the field (Jill Tarter, Frank Drake, Seth Shostak, etc.).
This post will be scattershot, because I have too many thoughts to get down without this becoming a novel. Overall impressions, though: I learned so much, my talk went well, and I met many important and interesting people. The atmosphere of the conference suggested that it went better than the organizers and participants dreamed that it would. Some of the discussions that arose naturally (about, for example, post-biological life or the role of science fiction in SETI) were fascinating and complex. The interdisciplinary angle was really rewarding and I saw firsthand the value of including all of these disparate fields in SETI. With the exception of ~4 talks that I just didn’t buy the premise of, I thought that the ideas brought forward were valuable and I very much enjoyed the experience of attending an event where so many of the talks were outside of my own area of expertise.
I Heard a Lot of Terms That Are Not In Our Terminology (aka. Why Defining a Standard Terminology Is Desirable)
I became more convinced of the necessity of my own talk by going to this conference. Everyone uses different words! Just look at the list below for a small sample. It’s honestly a mess.
Some assorted interesting terms I heard at the conference… SETT, SETB, Multi-Dimensional Haystack, Techno-signatures, Spiritual, Interstellar Archaeology, Artificial, CETI…
Modifications
“Artificial” is a word we will have to define – turns out it’s ubiquitous, contentious, and tough to pin down
Jill Tarter suggested that CETI be given a place in the taxonomy – I think this is a fair point, as it is functionally distinct from METI
The word “civilization” was in virtually every talk, in the way that we wanted to use “ETI” – that one might be a losing battle. I even found myself falling prey to that usage! It might be too ingrained at this point to change.
Michael Garrett suggested that perhaps “Schelling Points” is too unfamiliar to the field, and too Western, and an alternative might be better
Random Factoids I Learned
Exoplanets are part of the Mormon doctrine, and Jake Garn, a Mormon senator from Utah, defended the existence of SETI to Congress back in 1993
Menzerath’s Linguistic Law: Many applications and a mathematical formula (!), but essentially, the longer your sentence, the smaller the individual words that comprise it
There’s a Rosetta Disk on comet 67P! Talk about artifacts…
You can see the results of the Columbian Exchange in the Earth’s climate history: the rapid, large-scale death of so many people caused fields all over the Americas to fall fallow, causing a detectable CO2 signature
Paul Davies first heard of the term “technosignature” from Sara Walker
Ideas I’m Mulling Over
Ephraim Fischbach’s idea that neutrinos may drive decay rates in radioactive isotopes and thus these isotopes can be used as directional neutrino detectors. Would be very cool if it works, seems contentious. Potential applications include a study of interior solar activity, solar flare detection (the neutrinos seem to precede solar activity by about forty hours), a neutrino survey of the night sky, or maybe a communication SETI search for direct “prime number”y messages, or even a biosignature search for species that get their energy via fusion/fission
Terrence Deacon’s statement that natural languages come about via a process subject to several overlapping constraints. Many of these constraints could vary immensely in an extraterrestrial intelligence (environmental factors that shape language, for example), but semiotic constraints (having to do with syntax and grammar) are universal, and will not vary across languages
Mary Lee Jenswold’s argument that chimpanzees are very intelligent, based on their facility with sign language. At a few years of age, their vocabularies, grammar, number of utterances, and responses to questions are comparable to human children of the same age. They continue to sign into adulthood, teach their children the language, and talk among themselves. In addition, they understand more tacit rhythms of human conversation: they imitate, take turns speaking, shift eye gaze when they are the speaker, adjust their statements when misunderstood, and speak differently to various speakers.
Media I Heard Referenced That I Want to Consume
Edmondson and Stevens (2003) – The Utilization of Pulsars as SETI Beacons – paper
“One Strange Rock” – documentary, comes out March 26th [Update: Have seen the first episode, and it’s awesome!]
Turchin et al. (2017) – Quantitative historical analysis uncovers a single dimension of complexity that structures global variation in human social organization – paper
Other Minds: The Octopus and the Evolution of Intelligent Life – Peter Godfrey-Smith – book
Zipf (1949) – Human Behaviour and the Principle of Least Effort – paper
Our Final Hour – Martin Rees – book
The Future of Life – EO Wilson – book
Reinventing the Sacred: A New View of Science, Reason, and Religion – Stuart Kauffman – book
Things I Think the SETI Community Should Do
Have a central place (website?) determined by a group of people (committee?) for terminology – I was asked about this a lot
Get the literature in order! Have a central place, with tags and searchability, for all explicitly SETI papers (Alan is being awesome and working on this as we speak)
Create a searchable list of previous “candidate” signals, a thorough but public-level description of them, and their Rio Scale 2.0 assignments
Get a major article out to the public (NYT, The Atlantic?) about how dire the funding situation is for SETI, and stress that the search for extraterrestrial intelligence has not gotten a single cent from the government since 1993 (I would suspect that most people assume that SETI gets government funding). A large enough public uproar (#FundSETI ?) could maybe force NASA’s hand
Have a central mailing list or address book or organization (the Federation?) for SETI scientists all over the world, regardless of field or affiliation with SI, BL, etc.
People I’d Like to Follow Up With
David Raggozine – wants to submit proposal to look for weird transit signatures (residuals a la Arnold 2005, laser modified transits, megastructures, etc.) to test the NASA Astrobiology call wording. Jill Tarter was in favour of a submission in order to force them to take a stand. I want to get in touch with him, as Jason and I were thinking the same thing
Michael Oman-Reagan – I owe him an interview about my own experiences in the field, probably over Skype/phone sometime in the next few weeks
Graham Mcintosh – Talk was about using AI/machine learning to look for anomalies in astronomical datasets and challenging the scientific community with them. I’m interested in both his proposed search for these anomalies (already existing datasets! outside the box! hasn’t already been done! cheap-ish!), and creating a list of exotica – idea came up multiple times already. Maybe contact him about proposing and trying this with a single dataset as a proof of concept, (could even tie in with suggestion to David Raggozine?) then, if successful, pitching to SI?
Frank Drake – as a question after my talk, he suggested putting together a committee to codify and modify the taxonomy – something to follow up on!
The article “The Beautiful Intelligence of Bacteria and Other Microbes” in Quanta Magazine, by John Rennie and Lucy Reading-Ikkanda, is not your typical SETI paper. But maybe studying the behaviour of these “simple” creatures could give us insights about intelligence and anthropocentrism.
The entire point of the article is to explain how some single-celled organisms, individually some of the simplest forms of life, can congregate in biofilms and slime molds that collectively “solv[e] problems and contro[l] their environment” in a form of “cellular intelligence”.
The article is full of beautiful time-lapse photography from the lab of Harvard’s Roberto Kolter. Most SETI papers don’t have such stunning visuals – the “traditional” astrobiologists have us beat there.
Isn’t this expanding bio-film COOL?!
Examples of “cellular intelligence” given in the article include mapping terrain, forming complex wrinkled structures to allow all of the individual cells to have access to oxygen (see the .gif above), the differentiation of edge cells to allow “dendritic swarming” (a means of rapid colonization), and self-recognition / elimination of other strains and species near it. This was surprising to me, as it seems somewhat crazy to me that a ton of single-celled organisms have the capability to organize and accomplish such complex tasks. The analogy to artificial intelligence is made in the article, and that’s the best way that I’ve found to think about it: a lot of simple, single lines of code can form something that executes complex and surprising behaviour (ex. neural networks), so it seems reasonable that biology can do the same thing.
The thing that struck me the most, however, was the description of the way that biofilms repel “freeloaders”, discriminate against adjacent colonies that are too genetically divergent, and even stab nearby intruders with the bacterial equivalent of poisoned spears. The article calls the strategy “kin discrimination”. To me, this feels uncomfortably close to some of the less generous aspects of human nature.
And if mats of single-celled organisms, some of the simplest and most primitive life forms on Earth, show these particular characteristics, why should we be surprised if extraterrestrial single-celled organisms show the same characteristics? These same single-celled organisms might share a last common ancestor with the intelligent alien life that we’re looking for with SETI.
Life itself, thorny definitional questions aside, reproduces and metabolizes. And if something is preventing one of those two things, life needs to defend against that, or die. That brutalism, driven by practicality, might not be some base nature of humanity, but a base nature of life itself at the level of single-celled organisms.
Philosophical ramblings aside, the implications for SETI, to me, are pretty clear: should we be surprised if alien life is tribalistic, hostile, territorial, species-ist, and/or altogether terrible? It’s not like humanity, the only intelligent life we know of, has managed to overcome these tendencies yet.
How immutable are our social media consumption habits? Very few people would argue that immutable and social media should even be in the same sentence, except perhaps in that electronic paper trail that we leave behind us (“once it’s out on the internet you can never take it back!”). Vine, YikYak, and MySpace are just a few of the corpses that litter the social media platform floor.
With all of this in mind, #FoundThem, Duncan Forgan and Alexander Scholz’s paper about having SETI announcements keep pace with modern news consumption habits, is at once necessary and illuminating and simultaneously overly optimistic and prey to its own criticisms.
The authors consider the very important problem of public outreach and media image at a depth that most SETI scientists probably don’t think about. They argue that being aware of SETI’s perception in the media and taking active steps to prevent misunderstandings, preempt leaks, combat misreporting, and discourage sensationalism are a fundamental part of doing SETI science, and that proper protocols should be established and followed in this vein. It’s hard to argue with the sense in that!
But the execution of the idea would certainly be hard to pull off. Convincing scientists to coherently and publicly write about their methods before a search is even conducted seems whimsical at best. Old habits die hard, and changing the career habits of a generation of scientists is probably impossible. There’s an overriding fear of being scooped (see the 2003 EL61 incident) that makes some scientists wary of public information. And then there’s just the natural non-linearity that comes from being scatterbrained and/or busy and/or having organically evolving projects.
The authors argue that news is changing and that social media platforms will come and go. They give examples of Twitter, YouTube and Vimeo in their final section summarizing their proposed protocols. There are so many questions that this raises for me. The authors admit that the platforms are changing, but implicitly assume that, more generally, video publishing, “microblogging”, and medium to long form blogs will maintain popularity. I don’t have a good sense for how good an assumption that is, but perhaps they should’ve kept their suggestions more general, such that their paper will be relevant for longer.
In addition, the form of the content is not well discussed. Should these platforms be utilized to leave a publicly accessible research blog, polished and written for a general audience? Or just research notes, to leave a nice trail of proof but without the humor and shine* that you might include in a piece that’s actually meant to get “likes” and “retweets” and “views” and “shares”? Or just a video of a scientist at a desk, reciting the day’s progress in a jargon-y monotone? All of them require additional time which will not be spent doing science, some far more than others.
Suggesting that the journalists clean up their act instead seems disingenuous – like shifting the burden because we SETI practitioners don’t want to deal with it. At the same time, however, I feel like the most meticulously kept blog will fall like a domino in front of a single determined journalist with a sensationalist pen. Raise your hand if you’ve seen the Rio Scale used in an article (or even heard of the Rio Scale). My point exactly. Even if we could be as careful and involved with outreach as the authors suggest, the root of the problem might be deeper than a familiarity with WordPress can cure.
*some authors are probably incapable of humor and shine – what should they do in this case?
I don’t really know why you would want to build a city on a Kuiper Belt Object (KBO), but then again, I’m not an alien.
We thought the aliens were watching I Love Lucy, but maybe they’re watching Cowboy Bebop instead
Loeb and Turner (2012) make an argument that artificial lighting could be a good universal “lamppost”: something that all technologically advanced species would do so as not to be subject to the whims of a diurnal cycle. I can think of quite a few problems with that: a species that evolved in a sub-surface ocean, species on tidally-locked worlds that never had a diurnal cycle, the ever-popular “post-biological life”, etc.
But okay, sure, let’s say everyone needs street-lamps. With current technology, we would be able to detect artificial lighting (on the scale of a large terrestrial city) on KBOs in our own solar system. Regardless of plausibility, that’s pretty cool!
That part is in bold because it’s obviously the way this paper came about. I don’t think there are any good arguments for why KBOs are the best place to search for extraterrestrial life. I’m open to being proven wrong, but the paper reads as a fun thought experiment based on a new technological capability rather than any serious suggestion for how humanity can find another intelligent species.
The authors discuss a characteristic “flux-distance signature” that an artificially illuminated object would have. Based on a double r^2 relation (one in sunlight reaching the object, one for the backscattered light), a KBO that’s just reflecting naturally due to its albedo should increase in brightness by a factor of r^4 as it comes closer to the sun. Meanwhile, an object dominated by artificial illumination would only increase by r^2 as its source of luminosity approaches. Thus, if we notice any objects with this r^2 relation, we should really take note because that would be really weird.
The authors also discuss caveats and confounders of this idea (phase angles, outgassing, albedo variations, rotation, binary companions…), but indicate that all of these should be periodic with the exception of outgassing and should average out over years of observation. They also briefly talk about how this idea could be applied to exoplanets (with phase curves and such), but it doesn’t seem like the the technology is there yet.
This definitely felt to me like a good example of Davies and Wagner’s proposal of cost before plausibility in SETI work (discussed in a previous post). They outline the logic behind the method pretty well, but if they were actually interested in the results instead of the theory they should’ve looked more into which pre-existing datasets could be used to attempt this kind of work. Because if someone* was interested in actually testing this idea, and not waiting for LSST etc., it would be nice to be able to hit the ground running on it.
As I indicated in my first sentence, I don’t really see a reason why there should be artificial lights on a KBO. They’re cold, they’re small, they don’t have thick atmospheres, they have no access to non-Kuiper Belt resources (what, you wanted something other than ice and dust?), etc. That said, if the search is easy to do and we can clear out some parameter space… perhaps it’s worthwhile.
The approach of Davies and Wagner (2013) is a good one as far as SETI papers go, so I’ll start with a quick summary of the salient points.
The primary point of the paper is that a search of data from the Lunar Reconnaissance Orbiter should be performed, looking for anything out-of-place that indicates the presence of non-terrestrial artifacts (or NTAs, to borrow a phrase from Haqq-Misra and Kopparapu (2012)) or past non-terrestrial activity. The authors argue that the moon is a good place to search for artifacts for many reasons: it’s close and we have good, high-resolution data of it, the surface is unchanging (on a hundreds of millions of year timescale), and it’s tectonically inactive, so we don’t have to worry about the artifact’s signature being swamped by thermal/radioactive/magnetic processes from geological action (like we would have on the Earth).
Look at this cute lil’ orbiter
The authors then divide potential NTAs into four classes, based on assumptions that they openly admit are anthropocentric (which is refreshing, compared to some of the other papers we’ve read).
The first class is messages, things that are “deliberate” in catching our attention. One thing to keep in mind is how long the message might have been waiting there – the longer it needs to last, the harder it will be for us to find due to the trade-off of detectability and durability.
The second class is scientific instruments, which have a nice symmetric pro and con. Con: they wouldn’t’ve been made for us to find, so they may not be easy to spot or recognize. Pro: instruments need power supplies, and power supplies are more easily detectable (think solar panels or waste heat).
The third class is trash – things left over from prior expeditions and never cleared away – a category that humans are particularly good at. The authors make a case for searching in lava tubes – trash left there would be protected from asteroid impacts and could lay undisturbed for far longer than something on the surface. I’ll be the first to admit that lunar spelunking for alien artifacts sounds like the most epic job posting ever, but it probably isn’t realistic to expect that a search like that would occur any time soon, even if we had any reason to believe it would be successful.
The final class of NTA is “geo-engineering”, or scars on the moon’s surface left behind by some prior alien activity (mining? excavations? who knows). Features created by geo-engineering might be easier to spot with the data based on scale, but the difficulties come in trying to decide which features are natural vs. NTAs, and which features are even interesting in the first place.
At the end of the paper, having defined some idea of what we might be looking for, the authors give some examples of ways to search the already extant LRO photographic dataset for these features. I decided to organize and expand on their suggestions in the following table:
This table is specifically in reference to the problem of searching for NTAs in LRO photographs, but it could be easily generalized to any big-data SETI project, and even many big-data projects in general. I think this is a useful summary for thinking about the problem of big-data, and a good argument for why the multiple-pronged approach that was being tried by the authors is the way to go.
{Side note: I am a huge proponent for citizen science as a way to make scientific progress while educating and engaging the public. I participated in many citizen science projects in middle and high school, and led a Seafloor Explorer competition for 20 middle school students that classified the objects and wildlife in ~10,000 images of the Atlantic seafloor. The gallery below shows some of the images that my students got very excited about in the classifying process. Applying a citizen science strategy to SETI could be very useful…}
This slideshow requires JavaScript.
To end this post, I’m going to change gears and get a little philosophical for a moment. The authors make an interesting case for pursuing SETI in large, already existing databases – many SETI ideas are low cost and high potential reward projects and should be pursued based on cost over plausibility. I still don’t entirely know how I feel about that idea. Could that mentality be politically destructive for SETI in the current funding landscape, and should that matter if science is being done and progress is being made? Does it lend legitimacy to fringe-sounding ideas, like the genomic SETI concept that the authors mention (ex. this paper), or does spending a little bit of effort to test and debunk these ideas actually make the field better in the long run? Are we uncertain enough about the nature of ETI that disregarding plausibility and just prioritizing by cost is actually a more logically consistent way to go about the search?
I don’t have answers, but I think these are interesting questions and we should keep mulling over them.
