Such Strong. Much SNR. Wow!

Kraus (1979) is about telling the story of the discovery of the Wow! Signal, arguably the strongest candidate for an ETI transmission detected.

The Ohio State University Radio Observatory holds the record for the longest ET search ever performed. Non-SETI whole sky radio surveys in started in 1965, but funding was cut abruptly in 1972 leaving a world-class telescope unable to perform large-scale operations. At this point, it was decided to use a previously-built detector to try to look for ETI signals in the “waterhole”. A couple upgrades and a lot of unpaid student and volunteer work later, the radio telescope was running ~full-time on a routine SETI program.

In August of 1977, the search paid off with the detection of a transient, celestial signal that caused discoverer Jerry Ehman to exclaim “Wow!” in the margins of the data print-out. Even though the same region of the sky was searched for weeks afterward, no new signals were found.

The article reads weirdly like an underdog sports story. I’m sure the back of the book would read something like “No funding, no precedent, and no excuses. Can these scrappy buckeyes go against all odds and find the interstellar connection that many believe impossible?”. This does make sense though as this is a magazine article, not a research paper.

Some obvious next steps (for the follow-up article, of course) would be to see if this region of the sky had been observed since then and report back either on the tragic lack of signal or the tragic lack of observation.

Reaction to Oliver (1979)

In this document, scientist Bernard M. Oliver, a scientist and founder of Hewlett-Packard company, motivates the need for international preservation and protection of what he perceived to be the optimal window from which we may receive signals from extraterrestrial intelligence, namely the “Water Hole.” Among his many contributions to the fields of radio and electronics, he also had an interest in the Search for Extraterrestrial Intelligence (SETI). Prior to 1979, previous studies had already shown that the region bounded by the spin-flip transition of Hydrogran at 1.42GHz and the hydroxyl line at 1.66MHz was a prime region of frequency space to search for pulsed signals. At the time, several navigational satellites had been planned who would operate within these frequencies and disrupt such a search. Therefore, as a prophylactic measure, Oliver suggested a re-examination of the merits of the water hole and of the radio search in general.

He presents a case for electromagnetic radiation being the medium through which an advanced intelligent society would aim to transmit their communications and beckons to lower societies based on its satisfaction of multiple criteria. Important among these criteria are the need for the signal to be of low power, to not be absorbed or deflected as it passes through interstellar media and their corresponding electromagnetic fields, travel very quickly, and exceed the background levels. These criteria mostly preclude massive particles and favors low energy electromagnetic radiation, hence lending support to the idea of interstellar radio communications. He also presents a case that the water hole is the best window into the microwave and radio based on the low amounts of background contamination from contributions to the spectral noise power density like synchrotron radiation (which dominates below 1GHz) and quantum spontaneous emission (dominating above 60GHz). From free space, the case could be made for the frequency space between these upper and lower limits, however, when moved to the terrestrial frame, it becomes clear that significant portions of window are obscured by atmospheric molecular absorption. He also takes into consideration the motion of the Earth and the resultant Doppler drift, which increases the noise by a factor ^1/2, which dramatically builds the case for the hydrogen-hydroxyl water hole.

He admits to the romanticism and chauvinism of holding such a perspective, that water-based lifeforms would convergently arrive at such a bandpass for their communications. He acknowledges these shortcomings but insists that water is likely to be a common solvent for biochemistry to take place in throughout the universe, and contends that romanticism may be an inherent feature of highly evolved, sentient beings akin to humans.

 

 

A Review Paper and a Beach of Multicolored Rocks

This forty-page paper is a doozy, but so, so important. I only wish that we had an equivalent paper written in 2018 (Caleb and Will were brave enough to tackle this project – check out their work!)

[Warning: this post is also a doozy]

Tarter (2001) is a comprehensive review of the state of SETI as a field: where it came from, where it is, and where it’s going. This is important in a field with so many proposed projects and so few performed projects. I think it’s safe to say that most people assume that we’ve searched far more than we actually have, such that the Fermi Paradox seems very sharp. But unless you’re a proponent of very, very obvious, ubiquitous von Neumann machines in the Solar System, this paper makes it pretty obvious that we’ve barely scratched the surface of searching.

At that point in time, only 99 projects had ever been documented. I tried to see the comprehensive list, but unfortunately, the link to the supplementary material (it seems to be via seti.org) is broken. Hence, I can’t actually back up this statement, but I would guess that many of these were single/few target observations like Project Ozma.

It’s absolutely amazing to me that a paper written within my conscious memory can look so different from the scientific lessons and landscape that I’ve experienced less than two decades later (not that I was aware of the publication of this paper at six years old, but my point stands). Kepler was competing for selection, Huygens hadn’t happened yet, and Tarter’s plot of known exoplanets looks frighteningly sparse compared to the plots I generated effortlessly on exoplanets.org for Dr. Bekki Dawson’s graduate class on the subject. Tarter’s discussion of exoplanet finding techniques, however, and her thoughts on how the revolution would progress were incredibly prescient.

Things I Learned: I liked her explanation of the uncertainty principle argument to justify the search for signals that were unnaturally short in time or frequency. I had always thought of narrowband searches as the most obvious SETI search method (with much bias), but this is the best argument I’ve read for pulsed optical SETI having equal footing. Interesting sidenote: Charles Townes himself talked about how his invention could be used for interstellar communication.

I also did not know that there were distance-dependent effects that happen in both the optical (dust extinction) and the radio (minimum frequency resolution you care about because of broadening through the ionized ISM). I did not appreciate how interstellar scintillation could, frequency-dependently, affect the signal amplitude. This is a good reason to search for combs – I’d be curious to see if anyone has ever run a comb search, because if so, I’ve never heard about it.

There’s so much to say about this content-dense paper, but I’ll leave it off on a final point starting with the following mediocre metaphor I just came up with.

Mediocre metaphor: the search space is a beach of multi-colored rocks. We know we’re looking for something that looks out of place, but that’s all the information we have. If we only look for, say, paths in the black rocks, we might walk right by a conspicuous grouping of green ones, or an artificial stack of large ones. But add two more pieces of information: 1) there’s a particular kind of basalt on this beach which isn’t found elsewhere 2) geologists love to study it. Now there’s a very obvious reason for our unknown signalers to add something weird into the basalt – maybe they shape a column of basalt into a triskaidecagon (it usually forms hexagonal columns). Even if we (as the searchers) don’t know where to look and don’t see anything, the granite experts will notice that something is up.

This is the rationale behind looking for “impossible objects” (an intentional variant of the idea of “nature plus”): making a signal that almost looks like an astronomical object that would be studied in the normal course of a civilization’s scientific advancement… but with something weird about it. Pulsars that don’t follow physical rules, stars with weird emission lines, supernovae going off in the Fibonacci sequence. This eliminates a lot of the Schelling Point philosophizing (frequency/target/bandwidth/time/etc./etc./etc.) involved in guessing what a transmitting civilization would do, which I am very much in favour of, personally.

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.

Search for Extra-Terrestrial Intelligence at Capitol Hill

The paper by Stephen Garber delves into the politics and the history of the funding for Search for Extra Terrestrial Intelligence (SETI) by the National Aeronautics and Space Administration (NASA), and the opposition it has faced in the US Congress.

Garber starts off by reviewing the history of SETI. Its origins in the seminal paper by Cocconi and Morrison (1959), from where it moved on to Project Ozma, the proposed Project Cyclops, Serendip, and the establishment of the non-profit SETI Institute in California.

In the 1970s, NASA began funding SETI under Philip Morrison, and established a SETI branch at Jet Propulsion Laboratory (JPL).  However, 1978 bought along the first roadblock for SETI in the US Congress; where, Senator William Proxmire moved an amendment to stop funding the SETI research, something he viewed as a silly search for aliens. Timely intervention by Carl Sagan made NASA resume the funding in 1983. Come along 1991, and NASA formally endorsed the SETI programme, with the Bush government requesting $12 million in funding. This would have been to start the Microwave Observing Project (MOP). However, the reception given to this proposal at the Capitol Hill was adverse to say the least, an uphill task was at hand.

An affliction of the SETI programme is the ‘giggle factor’, which is how SETI is wrongfully associated with UFOs and Science Fiction. In the light of the budget deficit and this erroneous public (and sometimes Congressional) perception, NASA  restructured the programme as the High Resolution Microwave Survey (HRMS).

This restructuring, along with the efforts by Senator Jake Garn, led to HRMS being allocated $12 million for FY93, in part for a $100 million 10 year program.  However, the very next year the Senate approved a plan to terminate SETI. In the words of Senator Richard Bryan –  “This hopefully will be the end of Martian hunting season at the
taxpayer’s expense”. Starting then, SETI relied on private donors for its funding.

Moving forward 25 years, unfortunately the situation today (2018) is not much more favourable for SETI. As discussed in Wright 2018 , SETI is still not viewed as a part of astrobiology by NASA. Further, budget cuts in the sciences by the new Trump administration have not helped its cause. That being said, on a more optimistic note: SETI has been helped by an infusion of funds from the Breakthrough Listen Initiative. Though private funding of the Sciences is always welcome, it should not be a substitute for reduced funding by the Government in lieu of  buying more F-35s (each one costs about $100 million).

 

Fermi’s paradox is neither Fermi’s idea nor a paradox

The problem the paper is trying to address is that whether Fermi’s paradox is truly Fermi’s original idea and whether it is a paradox or not. This is important because the misinterpretation of Fermi’s original idea has lead to two time cancellations of NASA funding for SETI.

Fermi’s original question was “where is everybody?” which did not question the existence of extraterrestrial intelligence. He was questioning the feasibility of conducting interstellar travel. However, Hart (1975) and Tipler (1980) mistakenly treated this question as a conclusion which is the aliens do not exist because we do not see them. The difference between the two is that one is a question and one is a conclusion.

Further, the author argues that the Fermi paradox which really should be called the Hart-Tipler argument is not a paradox. Instead it is a reductio ad absurdum argument. They are disproving the existence of extraterrestrial intelligence by showing the absurd results they will get if they assume the extraterrestrial intelligence exists. However, there also exist many preconditions Hart and Tipler assumed for their argument which includes the feasibility of interstellar travel, the lifetime of civilization. They made assumptions which might not be true. Therefore, their conclusion depends on the assumptions they make. So it is not a true paradox since we can tweak the assumptions and make the counter argument.

The author also rebuts a similar argument which is there is no other extraterrestrial intelligence because we have not detected anything. The author argues that the incompleteness in the searching for SETI signal could be the real cause of not detecting anything.

My takeaway for this paper is how easily people will misinterpret other people’s ideas. Especially I think for Fermi’s case, the reasons this happened is because Fermi has never published his idea and he was already dead when the Hart and Tipler papers came out. If he was alive, he would clarify his argument clearly and it will not be called Fermi’s paradox today.

Fermi’s Paradox. Neither Fermi’s nor a Paradox

Gray (2015) is about discussing why the Fermi paradox is ill-named. The author firmly believes that the term is not only misleading in an attributive sense, but also in its conviction value. This paper falls squarely into the “explaining/dissolving/sharpening the Fermi Paradox” category.

As cited by Gray, the Fermi Paradox is described as “If technologically advanced civilizations have inhabited our Galaxy for timescales of approximately a billion years, and if some of these have engaged in interstellar travel and colonization, then why have we not seen physical evidence of their visits?” by Paul Horowitz.

The main points that he pulls out are that the doubtful ETI argument laid out in the “Fermi Paradox” actually originates in early papers by Michael Hart and Frank Tipler, and is only loosely connected to Enrico Fermi by an out of context quote from a dinner party. Apparently, he said, “Where is everybody?”, but, instead of doubting the existence of ETI, he meant that he thought the difficulty of interstellar travel was the reason for not seeing extraterrestrials. Ergo, use of Fermi’s name and reputation lends false credence to the arguments.

In response to the “paradox part of the phrase”, Gray states that the “Fermi Paradox” presents a fact (i.e. we haven’t found physical evidence of being visited by ETI) as evidence for the conclusion that advanced ETI doesn’t exist. This is not a paradox, just a leading question. One that has many possible solutions that aren’t the obvious one (there isn’t any ETI). That conclusion relies on several assumptions itself that may or may not be true (e.g. “interstellar travel is feasible, the Galaxy would be filled quickly” etc.).

The whole purpose of writing a paper about this is to help disentangle SETI from its murky public reputation. It seeks to strengthen the justification for SETI by weakening the power of a phrase (and set of ideas) commonly wielded against SETI supporters. I don’t think this type of paper would be very important in fields with steadier support. It “is important, because the Hart-Tipler argument (proposed renaming of the Fermi Paradox ideas) was cited as a reason for killing NASA’s SETI program on one occasion in the U.S. Congress, and under the guise of Fermi’s name and the claim of a logical paradox, it may continue to inhibit funding and research in that area of astrobiology.” The last sentence of the conclusion puts it all out in the open.

Along with Garber (1999), this paper shows the political climate surrounding SETI funding, which is not that optimistic (circa early 2000’s).

 

Reaction to Sagan & Newman (1983)

In this paper, Sagan & Newman respond to the faulty conclusions derived from the solipsist worldview and offer their response to the 1980 Tipler paper entitled “Extraterrestrial Intelligent Beings do not Exist.” In that paper, Tipler argues that the probability of the emergence of another intelligent civilization in our galaxy is so low as to have not possibly have occurred, and thus we are the only such example in the Milky Way. He justifies this assertion with a variety of lines of reasoning. Firstly, that the problem of interstellar colonization can be reduced to two components, namely: a) the development of rocket propulsion technology to the modern level, and b) the development of a universal assembler or von Neumann machine. Both of these he presumes are feats that ought to appear early on in the list of accomplishments of a mature technological society. Consequently, upon mastery of these technologies, the timescale for galactic colonization would only be some 300 million years, a value that is short relative to the age of the galaxy. Secondly, he uses Drake’s Equation to suggest that the probability of the development of spacefaring civilizations is something like 10^-11 based on biological arguments, and since there are something like 10^11 stars in the galaxy, it is reasonable to think that there may only be one. In response to this, Sagan & Newman point out that the inevitability and reproduction fidelity of von Neumann machines cannot be guaranteed. It must be either that the builders can guide the proliferation of the von Neumann machines or they cannot; in the former case, they could program them to obey a non-interventionist code and avoid systems where life has emerged, and in the latter their exponentiation will continue unchecked until they the dominate the matter of the galaxy.

Sagan & Newman also revisit a calculation performed relating galactic colonization timescale to the historical colonization time across North America. This paper and their previous work taken as a unit are valuable because they represent one of the earliest attempts to model the timescale for galactic colonization. Unfortunately, the glaring flaw in their simulation was to treat the stars in the galaxy as static entities and simply allow a bubble to expand outward from a localized region, similar to molecular diffusion. This ignores the dynamical shearing that occurs with a differentially rotating galactic plane, allowing the separations between the stars to vary, accelerating the mixing and hence shortening colonization time. A new model accounting for this feature would be a valuable step towards a more realistic estimate of t_col.

Nonetheless, they remain steadfastly neutral regarding the ETI question and denounce the conclusions of the solipsist viewpoint by insisting on an experimental radio search.

Sagan’s Quixotic Trip to Galactic Hegemony (and SETI Funding)

Carl Sagan and William Newman, in their 1983 paper, excoriate the solipsistic view of extraterrestrial intelligence (ETI) championed by Frank Tipler in his 1980 papers and seek to persuade the reader intelligent life exists outside Earth. The Tipler series argued that humanity was the only intelligent species in the Universe. Tipler surmised that if intelligent life were capable of interstellar travel and colonization, there should be evidence. Tipler presented a reduction ad absurdum argument (see Gray 2015) in that, for the conclusion to be valid, every statement going into the argument must true, even those not necessarily known to be true. One of the first concepts addressed in the rebuttal is that of the “von Neumann machines”. von Neumann machines are self-replicating probes (vaguely reminiscent of Bracewell probes) which Tipler argued an advanced civilization would release. For Tipler, the lack of von Neumann machines indicated the lack of ETI. Sagan and Newman saw no problem with the lack of probes and instead reworked the argument presented by Tipler. Due to the programming adherence of self-replicating automata, the Galaxy or even entire parts of the Universe could be reworked. Sagan and Newman argued that a lack of such changes was in line with Tipler’s argument against SETI, but they went further and speculated any advanced civilization would fear these machines as they could ultimately destroy their creators in their inherent need to replicate.

After dismissing the potential dangers of exponentiating automata, the rebuttal focuses on the feasibility of galactic colonization as one of the “more ‘conventional’ scenarios of biological and mechanical beings”. Sagan and Newman map microscopic models of colonization to macroscopic scales with a nonrandom dispersal model that behaved as a Markov process for long emigration time scales and a nonlinear partial differential equation for shorter time scales. The assumptions going into this were that (i) colonization required the large populations of a society and not a colony, (ii) colonies would be established in worlds devoid of life, and (iii) colonization would be focused near the civilization. These assumptions, while perhaps sound from an anthropocentric perspective, must hold true for the remainder of the calculation to be valid. The authors claim the selected model “describes all but the mathematically most catastrophic situations, and different colonization scenarios are reduced to the selection of numerical parameters”. These parameters were rejected by Tipler with his own approximation of a colonization velocity that would result in colonization of Earth within 1000 years. The authors argue that Tipler’s assumptions were wrong and instead the rate should be adopted for values after the 1700s. Finally, Sagan and Newman address the lack of colonization might be a result of the short lifetime of advanced civilizations, particularly if they aggressively colonize, as they could self-destruct with of weapons of mass destruction. On the opposite extreme, civilizations that reach a quasi-permanence may be inherently peaceful and naturally avert colonization.

To this blogger, Sagan and Newman present a logical argument with a foundation of fiction bolstered by knowledge of human history. This does not detract from the efficacy of the message within the paper. If anything, the proclamation that “the Milky Way Galaxy is teeming with civilizations as far beyond our level of advance as we are beyond the ants, and paying us about as much attention as we pay to the ants” provides significant support to the search for ETI (SETI). While there is little scientific merit in this argument, the political repercussions are of great consideration. It is no surprise this article was released around the time NASA terminated initial funding for a SETI programme (see Garber, 1999). Sagan and Newman form a strong logical basis to dismiss the pessimism of Tipler while providing order of magnitude calculations that would warrant the funding of another SETI programme. Soon after this publication, Sagan talked one of the staunchest ETI doubters, Senator Proxmire, to convince him of the scientific merit and potential existence of life elsewhere. While a scientific critique of this paper falls flat, the sound logic and calculations suggesting intelligent life could exist without galactic hegemony would certainly rebuff ETI deniers and potentially foment future inquiries into SETI projects.

Galactic Peace Sounds Pretty Nice

As a matter of course, any astronomer has an intellectual understanding that Carl Sagan was the face of popular astronomy for many years. But as someone who was born the year before his death, I never got to experience that era first-hand. Now, reading his writing, I’m struck by the gorgeous simplicity of his arguments and the philosophical grace of his writing, and I understand more readily the “legacy” (if you will) of his name.

All of this to say: I absolutely adore the first paragraph of his 1982 paper with William Newman, “The Solipsist Approach to Extraterrestrial Intelligence”. I wrote a similar paragraph to kick off my undergraduate honor’s thesis, but this was the poetic distillation of the argument that I was aiming toward (and definitely didn’t reach).

Anyway.

The main argument of the paper is a contradiction to Tipler’s “solipsistic” argument that if there were other intelligent beings in the universe, we would’ve seen von Neumann machines in our own solar system; we haven’t so there aren’t. Sagan and Newman correct some of the more optimistic values in Tipler’s order of magnitude calculation. This originally made me very happy, as I felt rather uncomfortable with Tipler’s isotropically expanding, quickly replicating, unsupervised von Neumann machine argument in the paper we read for Tuesday.

The last part of the paper is a more philosophical argument than a mathematical one. I had never actually considered the “intrinsic instability of societies devoted to an aggressive galactic imperialism”. I always found that the “they blew themselves up” solution to the Fermi paradox felt too convenient: did they ALL blow themselves up??? But considering Sagan and Newman’s reasoning, I actually changed my mind about that line of argument. They contend that aggressive, imperialistic societies, like those of Colonial European times, don’t actually survive to become galactic powers because of the deadly combination of infighting + nuclear weapons. It is possible to survive such a stage, but only if you’re a group that is “pre-adapted to live with other groups in mutual respect” through (essentially) Darwinian means. So the ones that remain will be respectful and probably a little more hesitant to run around randomly colonizing or unleashing hostile von Neumann probes on the galaxy. It’s an interesting idea, though it would probably be dangerous idea to apply as a blanket statement.

Maybe the whole galaxy looks like playing a peaceful civilization in one of my favourite videogames from my youth: Spore

It ends, in Sagan-like fashion, with a caution that the question of ETI can never be resolved without an actual observational program / search, and no philosophical arguments or hypothetical calculations can be a substitute for that real, quantitative effort.