Author: Mariah MacDonald

Intelligence before humans??

Wright (2017) explains that that searches for ETI should include searches within the solar system. He argues that it is a good place to look (either for extant or extinct life), because it is near the only place we for sure know harbours life, Earth. He argues that life could have arisen on other bodies in the solar system (namely Venus, Mars, maybe the moon, the icy moons, and possibly asteroids or KBOs), and mentions that it is even possible that a prior species on Earth arose before humans that was intelligent.

I agree with many points in this paper. I believe that SETI should include solar system searches, especially because of the data we already have for many of the bodies. This links back to the argument by Davies and Wagner (2013) that SETI should be done not based on the possibility of discovery, but based on the time and effort the search would take. Solar system searches take remarkably less time since the objects are closer to us.

Wright points out that Venus could have been a good host of life before it lost all of its water and went runaway greenhouse. Unfortunately, Venus has such a young surface from its volcanic flows that any evidence older than a couple hundred million years would be completely erased, and any evidence prior would likely be erased too. Mars is a decent target since it was probably wet once and capable of hosting life before it lost almost all of its atmosphere, but weathering on its surface is decent and any artifacts would probably be covered by now. Other objects in the solar system and their associated datasets should be searched for technosignatures though.

That being said, there is a point in Wright’s paper that I very much disagree with, and that is the possibility of an intelligent species before humans. While I will grant that the fossil record is horrifically incomplete, one flaw I find in this suggestion is the need for oxygen. Our planet was very anoxic before about 500 million years ago, and the rise of life is highly correlated with rising oxygen levels. While any life could have been anoxic, most astrobiologists search for life that requires oxygen since it is the only life we know. Wright is calling for an analysis of ancient facies in search for technosignatures; I think this exceeds the “low cost” criteria, especially given that a successful search requires the assumption that any life inferred did not require oxygen. On top of that, although the fossil record is lacking, there is no indication of any line of evolution that was anoxic, nor evidence of a rise in intelligence that went extinct (unless we include intelligent dinosaurs?). This suggestion just seems fanciful to me; although it would be kind of neat, we have absolutely no reason at all to believe that such a species arose, no evidence of anything that could destroy such a species (except maybe KT?), and any intelligent life would need to be anoxic and would defy our current understanding of life.

SETI can be cheap; let’s do it

This post won’t really include much about Davies & Wagner 2013, expect for one line:

“[T]he criteria for searching a database should be primarily tied to cost rather than plausibility. If it costs little to scan data for signs of intelligent manipulation, little is lost in doing so, even though the probability of detecting alien technology at work may be exceedingly low.”

This is remarkably well said, and I completely agree. A huge argument against SETI is that nothing has been found yet, so it’s a waste to keep looking. While this argument is fallacious in itself, it can quite easily be rebutted with the above statement. If searching requires little time/money/effort, than there is no waste.

One great thing about SETI is that it (normally) does not require its own dataset. Astronomers are already observing interesting targets with different instruments at different wavelengths, either to catalog them or to look for anomalies. Any anomalies discovered will probably be scrutinized, so why not borrow the data and look at it from a SETI point of view? There are currently many algorithms searching datasets now (a solution to our big data problems), so altering these algorithms just slightly to look for expected ETI alterations or just anomalies takes minimal effort and, if the algorithm is light, has minimal computation costs. Such searches could even just piggyback off of current searches (flag anomalies) such that there is no additional computational costs.

Davies and Wagner specifically motivate looking through all of the wonderful data we have on the Moon, noting that because the resolution is so great, many artifacts/trash would be visible (assuming they aren’t buried in regolith). Personally I think that looking at these by eye is not the way to go, and that the search should be automated. It would also be neat if some machine learning were applied to find such artifacts, but this would require some kind of training set and therefore not only more work/time/money but also some kind of assumptions about the sizes and shapes of alien artifacts.

I think it would be really neat if someone were to dedicate some time (probably unpaid =/) to developing algorithms for finding anomalies in all of the (mostly planetary) datasets we have (images, transits, gravity anomalies, all-sky surveys in every wavelength). This would not take much, and the algorithms could just run in the background. Follow-ups for any flagged anomalies would include compilation of all possible data and either human or artificial analysis to somehow rank how anomalous the data are. This would simply be really awesome.

 

The face of a facies: when a face is just a (rock) face

In 1976, the Viking spacecraft orbiting Mars took a picture. Well, it actually took many pictures, but there was one of particular interest to some people at Goddard and then the general public. This picture shows a structure that looks kind of like a human face:

The paper originally suggesting this feature looked like a face was originally dismissed for a few reasons, but people did continue to study it. Carlotto (my guess is for his own curiosity and for the interest of the public) performed a fairly extensive analysis of the image above along with one taken 35 orbits later. He cleaned up the data as best he could and then, using the two images, attempted to make a 3-D reconfiguration of the rock to see if the features persisted. I must say, I am fairly impressed with this paper. Carlotto only presents his opinion, that the feature might be artificial, near the end of the paper and only in one sentence. During the rest of the paper, he focuses mostly on explaining his methods and analysis.

I would say that his only flaw would be trying to pull too much information out of his crappy data. I also feel he should have used the other two images (although low resolution), because two data points is simply not enough to make a proper 3-D model of anything, especially if they two data points are from roughly the same angle at roughly the same time of day (Mars day). His 3-D model results (which he displays from different simulated camera positions) look near exact to the original image:

I agree with the original non-believers though. We humans are great at finding faces in just about any kind of rock:  Old Man of the Mountain, the Romanian Sphinx, the Pedra da Gávea, the Old Man of Hoy, Stac Levenish, and the Badlands Guardian.

For anyone interested, here’s what the face looks like when you have nice data:

I mean, it looks really neat! It is still a nicely shaped, elliptical-ish mound. There even appear to be sand-drift (or maybe water) channels running off it. It just definitely looks like a rock though. This picture is courtesy of the Mars Global Surveyor from 1996.  The Mars Reconnaissance Orbiter (2005) also imaged this area, but it looks about the same as above: no face. And this kind of makes sense! If life were to take as long to arise on Mars as it did on Earth (which hopefully would have occurred when it was still wet), then any civilization would have been recently died out, and anything they left behind would be visible yet subject to weathering. With its sad atmosphere and lack of water cycle, Mars no longer has as much weathering as it maybe did at one point, but any “face” made by a civilization would not last. (Also, who would make a mile long face?? At least our large structures on Earth are visually appealing when you’re next to them and don’t require spacecraft to admire.)

Just stick with lasers

Arnold (2005) is the first mention (I think) of using transits as a potential form of communication. Arnold suggests that advanced civilizations could embark on ridiculous engineering adventures and launch one or multiple crafts into orbit as a way to long-term communicate their existence. A civilization could launch a single, large object that would block out a substantial amount of the star (like a Dyson sphere), or they could launch objects far from circular, whose transit curves would have different ingresses and/or egresses.

Personally, I doubt this would ever happen with the intent of communication. Such a project would take so long to complete, and so many resources, that I doubt a civilization would bother. If they were to bother, I don’t think the intent would be as a form of communication.

Arnold mentions that civilizations could group multiple objects into prime numbers (his example is 11 objects with 1,2,3, then 5 objects). This just seems like pure fiction to me. I haven’t done any math or simulations, but I’m skeptical that it is possible to keep this many objects gravitationally stable while still maintaining transit alignment. And even if this could be done, it would quickly go unstable, with orbits deteriorating.

If people search trasist data for megastructures, which they have and will hopefully continue to do, I feel that they should just look for odd or anomalous transits, possibly even swarms. But I don’t think people should bother with looking for messages in transits.

19 Years Ago We Didn’t Find Aliens

Surprise! Bet you didn’t know that.

In 1999, Annis performed a simple “search”  for alien life. He hypothesized (probably correctly) that a type III Kardashev civilization, one that controls power comparable to an entire galaxy, would be an outlier on R-I-T relations, where R is the size of the galaxy, I is the intensity, and T is the temperature. Both spiral and elliptical galaxies have such relations, Tully-Fisher for spiral and the fundamental plane for elliptical galaxies. He also theorized that such galaxies would have an excess of IR radiation and would have low surface brightness. Using data on 106 elliptical galaxies and 57 spiral galaxies taken more than a decade before he published his paper, Annis looked for any outliers in the above relations. He defined his outliers to be objects more than 1.5 magnitudes dimmer than the emission predicted by the respective relation. This seems fairly safe, and like a sound argument for detecting life. Personally, I don’t see any civilization becoming a type III civilization, so I consider this and related searches to be a decent waste of time (for SETI; some of the searches lead to important science).

Not surprisingly, Annis found no objects that met his outlier criteria. I say this isn’t surprising for two reasons. First, I feel that a galaxy with anomalously low emission would have been flagged prior to this search given how long the data were available. Second, this search was of so few galaxies. (A weak third argument would simply be that a civilization capable of eating up energy on the order of their galaxy would have ways of compensating for this fact, like Kipping 2015 suggested covering transits with lasers.)

This search to me just seems a bit useless and like he had a free afternoon and wanted to just quickly write up and publish *something*. Even if he were to find a galaxy with too low emission, it would require additional data in some other field to confirm it had anything to do with ETs. That being said, I would be interested in seeing someone do this with all the data we have nowadays.

Dyson Spheres: Fiction or Fantasy? (definitely not vacuums)

I don’t mean to just flat-out say that Dyson Spheres are impossible (even though they are). Instead, I separate their possibility into two categories: “fiction” and “fantasy.” Here,  fantasy is something thought up by the imaginative yet impossible (think wizards and dragons) but fiction is something thought up that *could* be real. Maybe.

In 1960, Dyson wrote an article (letter?) to Science, stating a fun mind experiment that he had come up with: that advanced civilizations could build a “biosphere” (later called a Dyson sphere) around their star out of some outside matter (e.g. Jupiter), successfully harnessing all of the power of the star and solving over-population problems. This biosphere would block radiation from the star to outside viewers, except in the IR. Therefore, Dyson argued, we should begin a search for objects with strong IR emission and not much else.

It’s hard to discuss this paper without mentioning some of the published responses he received and his rebuttal to them, mostly because some other people basically mentioned my arguments to this idea nearly 58 years ago. Maddox points out that a Dyson sphere is physically impossible. To keep this shell in orbit around the Sun at any distance in the Habitable Zone would require some force counteracting gravity and pushing outwards on the sphere. In stars, this is radiation pressure. Maddox points out that radiation pressure wouldn’t really work, but doesn’t go into any specifics beyond that (it was only a short response). I wonder if there is any material strong enough that we know of or even theorize that would maintain its structure, so that the rigidity itself was counteracting gravity. Probably not, but still fun to think about. Dyson counters that by biosphere he imagined was obviously not whole as that would be impossible, but instead made of “a loose collection or swarm of objects traveling independent orbits around the star.” Wait, what? So even though it is a sphere, it’s not actually a sphere. But it is a lot of artificial bodies around the star..would that be bodies going the same velocity so having the same semi-major axis? Or are people just going to build a bunch of planets with different inclinations to fully cover a sphere? I can understand what s sphere around a star would look like, and agree that it probably is not mechanically possible, but I cannot figure out how “a loose collection or swarm of objects” would work at all. Personally, I feel this clarification terribly backfired. I had also always thought of and heard of Dyson spheres as being, well, spheres, so it seems that this clarification wasn’t read or remembered by most anyways.

Anderson then argues that such a sphere could not even be constructed. Since it would take so long to construct (several thousand years), there is basically no way that a civilization would bother continuing it. Sure, they could start, but after a few generations someone would come up with a better solution to over-population or for energy usage that would require so much less work and time. He argues that the only way this could work would be to go all Brave New World and condition people to accept the continuation of the project, in which case people could just be conditioned reproduce at sustainable rates! I completely agree with this argument, although I’m not sure how relevant it is to Dyson’s paper. It is true that a Dyson sphere is so unlikely to be produced that no civilization would do it, but Dyson spheres themselves aren’t really possible, so this seems like a waste of ink. I, however, do not agree with Anderson’s conclusion that “astronomical discovery of infrared sources won’t prove anything about the inhabitants of other planets.” I mostly don’t agree with this because we have no way of knowing for sure what we can learn from an IR signature until we actually start looking at them. Only slightly related to this, we can *detect* planets using their IR signatures (kind of, direct imaging in the IR is easier due to the slightly less horrible contrast issues); besides, as Maddox pointed out, an IR search would still be astronomically valuable, even if it wouldn’t lead to the discovery of Dyson spheres.

I personally believe that Dyson spheres under the definition of a solid sphere somehow encasing a star are impossible. The sheer force required to keep the sphere together would be insane, and no civilization would bother putting that much time and money into such a feet (we can’t even get funding to put man back on the Moon!). I can see the appeal of a Dyson sphere as it would lead to plenty of space for people and solar panels and such, but I don’t think it would solve over-population problems nor do I think anyone would bother making it.

Our Aliens are Just Like Us (and this could be a problem)

Michael Oman-Reagan is an anthropology student at Memorial University of Newfoundland, and runs a column on sapiens.org called Wanderers, dedicated to exploring “anthropological insights from our encounters with outer space as we study the origins of life in the universe, search for extraterrestrial intelligence, prepare to send humans to Mars, and imagine travelling to distant stars.” In an article from February last year (2017), Oman-Reagan discusses many possible differences that alien species could have compared to the human race. He goes into detail about specific things that we find hospitable, and many things that we subconsciously do that might be perceived as amusing or hostile (or beautiful or ugly).

Oman-Reagan concludes his article by saying that any hosting of aliens would require interdisciplinary tools as well as “anthropological insights about intercultural contact and our human tendency to naturalize and then universalize culturally specific behavior and beliefs.”

Although anyone who thinks about it will come to the conclusion that alien species will probably be unlike human, many people don’t bother to consider *how* unlike us the species could be. I think this is an excellent point! Even books/shows/films known for their variety of species keep alien cultures to be fairly mild and still akin to our own. I’ll list some examples of species below that are, at first glance, quite unlike our own. These species end up having one or two things different from us, but it is possible there exists a species that is completely opposite from us; not only would they look different, communicate differently, sense things differently, but they might enjoy everything we despise and be offended by the things we enjoy. Oman-Reagan points out that certain habits of ours are (in our culture) subconscious, that we do not do them intentionally to be proper or rude or kind or curious, and that many would not even think these things *could* have an impact on anyone. A good example is that we blink. We need to blink, in fact it is so hard *not* to blink that we have contests to see who can go the longest without giving in. If blinking is not required for a species as it is for ours, then maybe such an action could be seen as “beautiful, hilarious, offensive, or threatening.”

I personally had never thought of this! I have read and watched sci-fi for nearly all of my life, and yet when I think of aliens, I think of creatures that are actually quite similar to us (now that Oman-Reagan has pointed out how completely different they could be). Were I to interact with or host an alien species, I would not think about possibly offending them, and certainly not through actions we consider hospitable or through our anatomy or through subconscious actions. In my mind, anything that we dismiss as “only human” would also be dismissed by other species, but that isn’t necessarily true at all!

It seems to me that we cannot think of cultures that are far from our own (all of the below species blink!). We can create species in science fiction that look and act differently from our own, but we never stray too far from humankind. Given the lack of diversity in science-fiction species, it makes complete sense that Oman-Reagan would publish this article! If we do ever interact with alien species, and are able to communicate with and understand them within reasonable time periods, it will be quite important to keep in mind how vastly different from us they could be. Although it is possible, it is not guaranteed that they will be similar to the species in our sci-fi.

As promised, here are some examples of humanoid*** alien species from popular literature (I feel this is alright since Oman-Reagon included an alien species image in his article.) Buckle up, because things are about to get nerdy in here!

The Borg are a species of cyborgs from Star Trek. Although they technically are many species since they steal infants from other planets, give them implants, and make them part of the Hive, I’m going to consider them their own species for now. The Borg operate as one, linked by a hive mind. They aim to achieve “perfection” by assimilating species, technology, and knowledge. Their only requirement is energy, which they receive on their ships in small, personal alcoves. As portrayed in the show, the Borg are considered dangerous and ruthless. They are technologically advanced and seek out knowledge and species to assimilate. Although they seem quite different from humans, they aren’t super different. I would argue they are similar, just lacking culture. There’s no way to amuse or offend one of the Borg drones, as they value only knowledge and perfection. Without culture, they are simply beings following a single ambition.

More Star Trek! A reoccurring race in New Generation and Voyager is the Q. The Q are immortal, intelligent, and have the ability to control space, time, matter, and energy. They evolved over centuries to what they consider to be the “state of ultimate purity.” They are apparently absurdly intelligent. This trait, matched with they abilities, makes them quite apathetic to basically everything. One specific Q, named Q, spends episodes messing with the crew as a form of entertainment since the species had already accomplished everything that could be accomplished. Although god-like, Q himself is quite similar to humans. He can be entertained and annoyed, in ways similar to humans. He can also be petty and annoying himself.

The Silurians are a reptile-humanoid species in Doctor Who. While they look quite different from humans, they still have the general humanoid shape, size, and mannerisms. Although they are telepathically linked to one another, they are capable of speech and use it when communicating with other species out of kindness. They are generally peaceful, and in fact are forbidden from warfare except in defense. They believe in keeping their species pure, and follow a religion similar in kind to many religions we have. They value art, sports, and games, but at what level is not really discussed. They even have poetry composed of optical illusions! The Silurians are, in fact, quite similar in culture and anatomy to humans.

The Trees of Cheem are an intelligent race of humanoid trees. They do not understand technology and give clippings of their relatives as gifts. They all have retractable vines on their arms, but showing these vines is considered highly inappropriate. The species, although wealthy, is wise and compassionate. The Trees can feel any pain from vegetation on their planet, and usually keep it quite protected. Although they don’t have technology and say they do not understand it, they are able to use it. They are also quite clever and able to successfully judge the character of people. This species, an evolved form of tree from Earth, is also quite similar to humans! Their mannerisms are similar, and aside from giving away body parts and being flammable, they seem near identical in culture and personality to many humans.

The Ood are another species from Doctor Who. They are unable to speak vocally, communicating telepathically. They are humanoid with tentacles on their face (for eating) and the color of their eyes indicates the level of telepathy currently used. They have very long lifespans. They technically have three brains, one in their head, one they hold in their hands that is connected to their face, and a large communal brain that hosts the hive mind. They are a gentle and harmless species, and are generally considered less advanced than humans. They have a leader, and they sing to portray their emotions. When they are enslaved, they are in pain and quite sad. When they are freed, they are filled with joy.

Again, I would argue that these alien species, although seemingly different from each other and from humans themselves, are quite like us! They have communication, wealth, ambitions. Many of them can be pleased, offended, angered, and amused. In making alien species, it seems that levels of intelligence, technological dependence, and emotional range are simply plucked out of a hat and put into something (usually humanoid) and proclaimed alien. However, all of the technologies and intelligence and emotions are those imagined (or used) by humans, in ways that humans would or do use them, so even the species in science-fiction are quite similar to humans. Since most (maybe all?) of us are exposed to the idea of alien species through sci-fi, my guess is that we all have a similar idea to what aliens will be like, and although we will consider them to be different, we would not consider the possibility that they could be as vastly different as suggested in Oman-Reagan’s article.

 

***I only included humanoid species in this list because, in popular culture, non-humanoid species are 80% of the time just evil and trying to kill humans, 15% of the time pets or pests, 5% of the time alien-looking with exact human personalities and/or cultures.

 

Earth to ET, come in ET

On November 16, 1974, the Arecibo radio telescope in Puerto Rico sent out a message to the stars (specifically those in M13, a cluster 25000ly away). This message, in binary, was the first emission from Earth with the intent of someone else receiving it. And here it is:

Isn’t that sexy? For those of you who can’t read binary and/or have no idea how to break this code (probably most everyone on this planet), the message is decoded into groups of 23 characters, leaving 73 groups. The authors explain that because these numbers are prime, this would clearly be the right way to interpret this. Personally, I would never get there. I wouldn’t think there to be any significance in the number of characters per line, or what have you. Once you know how many characters should go into each line, this looks a little bit more like something that could be interpreted:

This personally reminds me of Christmas sweaters, nonograms, or the early Atari games, but there is meaning to it. The first line indicates the numbers 1 through 10 in binary. Apparently the numbers 8, 9, and 10 are too large, so they are written differently? I’m not sure I really understand that even with a decent explanation from the authors, which makes me believe that anyone trying to decipher this would have an even more difficult time (I suppose they could just be remarkably more clever than I).

After these numbers, there is a “description of fundamental terrestrial biochemistry.” Although I can pretend to see the 1-10 numbers, I have no idea where they biochemistry stuff is (apparently lines 12-30). First comes the numbers 1, 6, 7, 8, and 15, indicated the elements H, C, N, O, and P. These elements are required for life as we know it (although some might argue the importance of other elements). After these numbers are chemical formulae of molecules or radicals (the paper doesn’t say which ones). Included in here are the structures of the molecules that make up DNA, in the structure of a double helix, and the number 4 billion to indicate the number of molecular pairs (adenine-thymine or guanine-cytosine) in DNA in a single chromosome.

Below all this is a representation of a human! We are bipedal with arms and a head. This comes with the number 14, indicated that the human is about 14 units tall. The units are (apparently obviously) the wavelength of the original transmission.

Below the human is a schematic of the solar system; the big blob is the Sun, then all nine [at the time] planets. The length of each bar is a semi- indication of the planetary size, and the third dot from the Sun is us! It is slightly placed out of plane, in an attempt to indicate that that planet is where humans reside. I would interpret it as the planet’s inclination, but that’s okay.

Below our solar system is a drawing of Arecibo. I would never guess this, but that’s what it is. This drawing is accompanied by the size of the telescope, my guess is with the hope that any response would take into consideration our limitations and make sure that we could actually hear them.

This message was put together by numerous people, and is quite creative to say the least. That being said, I am extremely doubtful that this message could be interpreted! For starters, the only way I could make heads or tales of it was from the picture directly, and that was after the whole 27-73 thing was implemented. But what if the receivers only caught part of the transmission? It took 169 seconds to send, so it is possible that only a minute or less would be received if the receiver was not pointed at Earth for the entirety of the message. With only part of the message, there is nothing to indicate where each line starts or how long it should be. In addition to all this, it would take a lot of brain power to decipher all of it. Sure, some of it could be understood without much time, but to get all of the message would take work and prior knowledge. This all assumes that whomever receives this thinks in a way similar to how we do, and what is to say that they way we think is normal? What’s to say that clearly it is logical that the first line is just numbers, and then straight from numbers we switch to chemistry?

I do wonder, assuming that the recipient of this deciphered it, what the odds are for misinterpretation, and what the consequences of this would be. It would certainly be amusing (to read about, not to experience), if the compounds were interpreted as a cry for help, and some lovely civilization prepared them all and brought them to us in quantities large enough for our population (4 billion at the time). What if they thought that each of our chromosomes needed these compounds for each of the 4 billion people? Imagine an entire fleet of interstellar (or intergalactic) ships coming to our rescue in 50,000 years with buckets and buckets full of thymine (I don’t think you can just store that in a bucket).

I also wonder if a group of humans could decipher this. If we just gave this message in binary (we could also just send it via radio, but I’m not sure that would be picked up) to a group of intelligent, multi-disciplinary people, would they be able to pull out all of this information? This seems like an important sanity check (to me) for any METI that we do end up sending out. If we humans can’t decipher our own messages, with the culture and knowledge that went into its making, then why would anyone else out there be able to decipher it?

With all this being said, I should note that the people who sent this message did not really expect it to be received or answered, that this was just a proof of concept of the current technological capabilities. So whether or not this message is received, understood, correctly interpreted, or responded to isn’t all that important.

This Water Hole has Nothing to do with Buffalo (or zebras)

The “water hole,” as used in SETI, has nothing to do with holes and only a little to do with water (but not really). It is the range of frequencies between 1420 and 1700 MHz, bounded by the hydrogen line and the hydroxl line (H + OH -> H2O, so sort of related to water but unrelated still to holes). The idea of this water hole was first introduced in 1971 by the Cyclops study who suggested that this band was a place where “different galactic species might meet” just as animals meet at actual water holes.

In an attempt to resurface love for the “Water Hole,” Oliver wrote his paper “Rationale for the water hole” in 1979. This publication was timely in that many companies were submitting proposals and plans to fill this frequency band with what would be interference to astronomers searching for ETI. Oliver suggests (and I agree) that “it would be a bitter irony if the desire to know exactly where we are … were to prevent us from ever knowing where we are with respect to other life,” as many of these proposed technologies were for GPS. Oliver writes his paper methodically, going over requirements for any signal from ETI and arguing for the water hole.

First, any signal sent must be significant in respect to signal to noise.  Oliver immediately dismisses Bracewell’s probes as excessive and expensive. Therefore, the signal must exceed the noise, avoid scattering and deflection by the ISM and other mediums, and be easy to detect. Massive particles are excluded from this as they require too much energy to send and anything holding a charge would be deflected or absorbed. Although neutrinos are nearly massless, they cannot be generated or detected easily and are not usually radiated by civilizations, so no one would start by looking there. In contrast to all of this, light is massless and easy to produce and detect. Low energy photons are also not readily absorbed or deflected, making them a great signal.

Oliver argues for the microwave region as the optimal region since it gives the minimum detectable received power, and grants the smallest cost per unit of collecting area. It also allows for bandwidths narrower than optical. This region is also decently unobscured by the Earth’s atmosphere. Obviously, we need to be able to detect signals through  our atmosphere, but the signal would need to leave the atmosphere of other civilizations (assuming their life and atmosphere are alike to ours). The H and OH lines are also relatively quiet in respect to the receiver noise per channel.

All of this leaves a fairly wide band (2GHz), which is way too wide to search. And thus enters the water argument. Life on our Earth requires water, and water is decently common in the universe. It isn’t too difficult to take these two facts and postulate that most life in the universe probably requires water. So, searching for signals of water make sense. Why that means that the H and OH lines should be the borders of the band we search in, I’m not sure. I suppose the H and OH lines leave a decent sized band that is an appropriate place to search.

Since no better band has been suggested, Oliver argues that this band should be used for SETI and preserved for such reasons. He closes with a lovely quote “If we are to make progress we must proceed on the basis of what we know, and not forever wait for something now unknown to be discovered” that should be on scientific motivational posters.

I personally really enjoy this paper since it is methodical, scientific, and not just random, unsupported postulation. As of now, I’m not sure if the water hole is bogged down with terrestrial signals, but I hope not. I wonder if a call to action (or I supposed inaction) such as Oliver’s need be published every few years to remind people of why it is important. Something to look into.

Let’s Call it the Hart Argument

The Fermi Paradox is the term often used to describe the argument that since an alien species is not currently on earth (or since we have no evidence for ETI), they do no exist. This argument is often paired with the question “where are they?”, a question asked by Fermi in 1950.

Gray (2015) lays out the timeline surrounding the so-called ‘Fermi Paradox,’ arguing that the name is misleading and should not be used. The name first appeared in literature in a paper by Stephenson (1977). Given that this was years after Fermi first asked his (now) famous question “where are they?”/”where is everyone?”, it seems odd that it would be over twenty years before it was used. In fact, Stephenson (who coined the term, it seems) says that he merely put the two words together because both were used frequently in SETI conferences.

As Gray lays out, this term is quite misleading.  First, the argument that since we see no ETI, there must be none is by no means a paradox. There exists no contradiction in the statement, merely a conclusion based on a paucity of evidence and a variety of assumptions (e.g. space travel is feasible and colonization is the natural course of intelligence). Since there is no paradox present, this word should not be used at all.

Fermi’s initial question was not about the existence of ETI at all, but merely questioning the feasibility of space travel. Gray contacted all surviving members from the 1950 meeting where Fermi asked his question, and all three stated that the question was about space travel. In discussing the existence of ETI, Fermi’s name should not be attached. Instead, Gray argues that Hart (or Tipler) should be accredited with this argument. Both have written numerous papers following this logic, with Hart being the first in 1975, two years before Stephenson’s paper.

Unfortunately, the ‘Fermi paradox’ (by name and meaning) has been used multiple times in calls to stop SETI. Because of this, and the general misleading nature of the term, Gray argues that the argument should be renamed.

I am so happy that this article exists. Having BSs in Physics and Astronomy, I would assume (hope) that all the information I learned as fact in undergrad was true. One of the things presented to me was the Fermi Paradox; however, I now know that what I was taught was wrong. I was told that Fermi’s question was indeed about the existence of ETI and heard nothing about Tipler or Hart. I suppose that since I learned this in 2012, and this paper was published in 2015, this makes sense. Something led Gray to write this paper, and it was probably frustration involving the misleading name. However, Gray mentions numerous previous studies that call for a renaming, so I’m not sure why the curriculum remains unchanged. I do wish it would be renamed, maybe not to the public but at least in the fields of astronomy and astrobiology, so that new students can start out with the proper definition. I personally enjoy “the Hart Argument” since I enjoyed his initial paper in 1975, but any renaming the removed/replaced “Fermi” and “paradox” would suffice.