Reaction to Davies (2010): ”Nature Plus”

Davies, in this excerpt from his popular book The Eerie Silence, examines what we consider technology and how it may not necessarily apply to an advanced intelligence a thousand or even a million years ahead of us in terms of technological progression. He gives a definition of technology as “a mind, intelligence, or purpose blended with nature, which obeys the physical laws and harnesses them.” Therefore, technology is not distinct from nature in the sense that it is physically separate from nature, but is a part of and a higher form of it. It is “Nature-Plus.”

Classically, we recognized things as being artificial technology based on the organization and structure of its constituent parts, and its utility as a system. And also, such systems are macroscopic in scale. An example of such a system would be the modern personal computer, which is made of billions of transistors that come together to perform specific functions written in software, and which has occupies a physical volume on the scale of cubic decimeters. In fiction (and sometimes in bad science), there is a tendency to anthropomorphize the technology of an alien intelligence to follow our notions of machines.  However, on the deeper level, he calls into question even the aforementioned characteristics of technology that we take for granted, and posits that an advanced technology would be like nothing we would understand. We can imagine (but not yet understand) a technology that doesn’t manifest or operate on the material level, or which is indistinct in form or topology, or which transcends our one temporal and three spatial dimensions, or which to us appears as bereft of function, or which does not appear to consist of discrete quanta. An example of such a technology in fiction would be the “sophon” of Cixin Liu’s Three Body Problem, an intelligent particle which can communicate instantaneously across interstellar distances and which is formed of a circuit system sketched onto a multi-dimensional manifold and collapsed to a point.

If such notions of technology were real and currently in operation, then our theories of how the universe works may be called into question. And so, we should ask, what exactly is it about technology that makes it distinguishable from nature? The question is loaded because we operate on the premise that the nature we observe is truly natural. That is, astrophysical phenomena are emergent properties of a universe governed by the laws of physics. This however, may not be the case. We can imagine scenarios where those phenomena that were thought to be natural turn out to be artificial. Then, any theory of how the universe or its constituents operates that was based on such an observation would be flawed. This is similar in vein to the Planetarium Hypothesis solution to the Fermi Paradox, which suggests that the universe we see is artificially constructed or designed in such a way to make us believe that it is self consistent (that is, until we can muster enough resolution to “lift the veil” so to speak, and discover that the universe is not as it seems).

I think this idea of “Nature-Plus” should be taken seriously by SETI scientists because it challenges the way we think about nature and may be an explanation for why searches based on conventional notions of technology and energy consumption have been unsuccessful. And I do indeed think that it is meaningful to search for astrophysical anomalies, because of the twofold benefit of performing novel science alongside a SETI search.

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.

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).


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.

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.

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).


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.

Hart: There is no ETI therefore there should be no SETI

Hart (1975) is about asserting why the author believes that there are no other intelligent civilizations in our galaxy. That essentially makes this paper about addressing the Fermi Paradox.

The entire article is written about refuting different explanations for the fact that “there are no intelligent beings from outer space on Earth now”, which he puts into four categories: physical, sociological, and temporal as well as those that say that we have been visited, but the visitors are no longer here.

The paper makes its case by attacking each type of explanation individually. Physical explanations are refuted by providing some examples of future possibilities for long distance space travel and saying a sufficiently advanced civilization could figure it out. Sociological explanations aren’t valid unless they apply to all civilizations for the entirety of their existences. Temporal explanations are addressed by stating that it would be a mighty coincidence that a galaxy colonizing civilization evolved less than a million years ago (<0.1% of our galaxy’s age). The last category is address with a mixture of arguments from the temporal and sociological section.

Finally, anyone saying that the main fact is actually false and that aliens are here is wrong because few astronomers believe that. This point is added on at the end and I find it childish. I don’t really see the point of bringing up the possibility of the main fact being wrong if it is not going to be properly addressed.

This paper is interesting because it is the first paper that is openly against spending resources on SETI.

I feel like the paper takes a lot of logical liberties in order to make its point. Importantly, his conclusion is that there are no intelligent civilizations in our galaxy, and I think he means currently. When he makes his arguments against sociological explanations, he talks about how cultures change over millennia, so any intelligent civilization would eventually start venturing out to find us, but a critical point he never mentions (at any point in the paper) is that we don’t know how long intelligent civilizations last. A lot of his arguments (eventually their technology will advance, their cultures will change, their colonization borders will grow) fall apart when dealing with technological civilizations that only last a thousand years or so.

Searching for Ozma!

Princess Ozma?
No.   Project Ozma








The PSU SETI class with the Project Ozma 85ft telescope.


In his 1960 article for Physics Today, Frank Donald Drake (1930 – Now) discusses the rationale for searching for extra-terrestrial (ET) intelligent civilizations using radio surveys, and after doing so describes Project Ozma. Further, he lays the groundwork to quantify the probability of finding intelligent life, which was later formalized as the ‘Drake Equation’.

Project Ozma conducted at Green Bank using the 26 m (85 ft) diameter radio telescope, was one of the first SETI (Search for Extra-Terrestrial Intelligence) experiments to search for intelligent transmissions of ET origin. It included observations of Tau Ceti and Epsilon Eridani, two stars spectrally similar to the Sun. With the exception of a false alarm due to a secret military project, the project did not yield any significant signal from these two stars.

Drake starts off by discussing how later generation stars contain not only Hydrogen and Helium but also metals. These metals (heavier elements) are required to form solid bodies like planets. Further, the formation of planets assuages the angular momentum problem in a cloud of condensing gas. Sun and other stars like the Sun have relatively slow rotational periods. This rotational period does not conserve the initial angular momentum and hence leads to a discrepancy. This can be solved by the introduction of secondary bodies like planets or binary stars, to which the gas cloud transfers angular momentum as it slows down. Drake suggests that as high as 60 percent of stars should harbour planetary systems.

Establishing heuristic arguments for their existence, Drake goes on to hypothesize whether life can arise on these extra solar planetary systems. He then cites the Urey – Miller experiment, which managed to successfully create amino acids in the laboratory using gases like ammonia, methane, hydrogen and water vapour and an electric discharge (simulating the early atmosphere and a lightning discharge). Amino acids are the building blocks of proteins which are the key ingredients for life. Therefore, the oceans were the harbinger of early life, which after about 5 billion years of evolution led to intelligent civilization. Drawing parallels to the origin and evolution of  life on Earth, he postulates the fact that since life would take so long (5 Gyrs) to develop and achieve intelligent civilization one can discount non main – sequence stars and those which have relatively short life spans (stars much larger than the Sun).

Another consequence of the comparison to life on Earth is the hypothesis that life needs liquid water to develop, due to which the planet (if it has water on it), cannot be too cold or too hot. This leads to existence of a narrow band around the star a planet can orbit – The Habitable zone. Being much closer, or much farther would lead to the vapourisation or freezing of water, respectively.

To search for such life on Earth – like planets around Sun – like stars, the use of narrow – band transmission in the radio is suggested. Discovery, and subsequent contact with such a civilization would likely be in the vicinity of the 1420 MHz region of the radio spectrum. This would be because it corresponds to the 21 cm Hydrogen line spin transition in neutral Hydrogen, a spectral feature that should be known to an intelligent life form. Also, in this region the cosmic noise signal is negligible making it easier to transfer signal at cosmic distances. On the other hand, even if we want to actively seek out ET intelligence this would be the appropriate EM region to seek communication in, since there is a greater possibility of such civilization having radio telescopes tuned and actively searching in this region of the spectrum.

Thus Drake lays the justification for Project Ozma where he searches in this radio band around two Sun -like stars (for princess Ozma?) . He concludes by stating the goal (of finding ET  intelligence) justifies the amount of effort required to carry out this work, and with the hope that in the near future, the search will be successful.

The Origin of Bracewell Probes

Bracewell (1960) asks the following question: How will civilizations of equal or greater intelligence try to initiate communication with nearby, unknown civilizations. He mostly elaborates on this by following semi-informal chains of thought. He argues that it is unlikely that they are running megawatt level transmitters pointed towards every nearby star that could possibly be hosting (or nurturing future) intelligent life. He instead argues that it is more feasible to search for life by sending out a swarm of armored, radio-transmitting probes to rapidly explore the nearby stellar neighborhood and a selection of further, promising target stars.

I think some of his reasoning is flawed here as one of his arguments against the interstellar transmitters is that they have a “dependence on our ingenuity in selecting the right star and the right wavelength”. It seems like he is suggesting that his probe swarm is a better idea than using a single transmitter. I would agree, but I think the swarm would be more comparable to using a network of many transmitters. Maybe the cost of building and maintaining thousands of transmitters continuously pointed at all of the targets is significant, but I would imagine the cost of launching thousands of autonomous probes would be pretty high as well.

He postulates that if there are already several advanced civilizations that know about each other, they will be connected and communicating, so we would only find evidence of the nearest community that is looking for us.

It is noted that by looking for probes within our own solar system we are in a way looking for signs that there are any advanced civilizations capable of reaching us. A cool idea. The probe within our solar system might only be a listener that reports back to home base via a star to star relay system.

This paper seems to have significance due to its documentation of several novel communication ideas and its introduction of extraterrestrial civilization network ideas.