SETI: A Fantasy Land

In his spare time, theoretical physicist, cosmologist, and astrobiologist Paul Davies exerts his role as an author. As his Amazon page describes, he has written at least twelve published books often on some existential question about life (or the dearth of life) in the Universe as informed by science. Davies has claimed he seeks to “bring the message of science and religion to the people” and, being a physics savant, was awarded funds from the Templeton foundation to support his research on “the natures of time and consciousness and extraterrestrial life”. One of his more recent books, The Eerie Silence, overlaps with his research interests and can be described as intellectually provocative.

Figure 1. Above is a popular image of what an alien would look like. Science fiction and pop culture have spawned this image as the most likely visage of ETI. The source is The Eerie Silence.

Davie’s book discusses SETI, focusing on its implications and assumptions. He dismisses the entrenched cliché of aliens (see Figure 1), as crafted by science fiction and movies. The end of chapter six and the entirety of chapter seven, “Alien Magic”, seek to question an important premise in SETI: that we know what we are looking for and it is something we can readily distinguish. Absent exotica, SETI seems a plausible and fruitful, albeit onerous, endeavor. The epigraph at the beginning of chapter seven is borrowed from Arthur Clarke and states “any sufficiently advanced technology would be indistinguishable from magic.” Davies describes the conundrum for a proponent of SETI:

If we were to encounter alien technology far superior to our own, would we even realize what it was? Think how a laser or a radio would seem to a tribe of rainforest dwellers who have never been in contact with the outside world. Now imagine a technology a million or more years in advance of ours: it might well appear miraculous to us. All of which presents new SETI with a serious problem. How can we look for signatures of alien technology when we have no idea how it would be manifested? In the previous chapter I suggested some ways in which an advanced civilization spreading across the galaxy might leave traces of its activity. But all the examples I gave were based on extrapolations of twenty-first-century human physics, and so are tainted by anthropocentrism. Suppose that alien technology is based on principles that are completely beyond the ken of our best scientists?

Figure 2. Above is a whimsical depiction of energy extraction from a rotating black hole seen in The Eerie Silence. A truck can be thrown into a black hole and ejected with more energy than it originally had thanks to the conservation of angular momentum.

At the end of chapter six, Davies presents the reader various exotic astrophysical objects that have yet to be discovered, but have been theorized by scientists. This includes magnetic monopoles, which could be recombined with the opposite monopole to produce energy that would dwarf a hydrogen bomb, and cosmic strings, which have been proposed as sources of fast radio bursts. Davies casually mentions one possible hypothesis for the apparent lack of these objects is the sequestration by a super civilization, but as he notes “the hypothesis that aliens are the correct explanation for the anomalous absence of something is only as good as the prior probability of an alien super-civilization in the first place”. His discussion of these objects brings into focus our current understanding of physics. Davies mentions an example, from John Wheeler, of what ETI could do to satisfy its energy needs (see Figure 2) while baffling humans:

Wheeler dreamed up the amusing scenario [in] which trucks containing industrial waste are dropped on a carefully calculated trajectory towards the spinning black hole. […] The trucks spill out their contents in such a way that the waste is devoured by the black hole. For certain trajectories, the empty trucks get propelled away from the ergosphere at high speed, zooming off with more mass-energy than the laden trucks originally had going in. Ultimately the additional energy has to come from somewhere, and in fact it comes from the rotational energy of the hole; every time the trick with the trucks is performed, the black hole’s angular speed drops a bit. The good times will not last for ever – eventually all the rotational energy will be extracted and the civilization will be obliged to decamp elsewhere. But at present human levels of energy consumption, a black hole could meet our energy needs for at least a trillion trillion years.

This is where Davies coins the phrase “nature-plus”. With our arguably limited understanding of the Universe, it becomes necessary to look past familiar proxies, such as energy or resource usage, to limit the bias from human understanding. Davies asks the reader to consider technology that:

  • is not made of matter,
  • has no fixed size or shape,
  • has no well-defined boundaries or topology,
  • is dynamical on all scales of space and time or, conversely, does not appear to do anything at all that we can discern, and
  • does not consist of discrete, separate things; rather it is a system, or a subtle higher-level correlation of things.

This emphasizes there may exist incomprehensible technology that operates on levels indiscernible to a human. Davies surmises that:

Technology is, in the broadest sense, mind or intelligence or purpose blending with nature. Importantly, technological devices don’t subjugate nature; the devices still obey the laws of physics. Technology harnesses the laws; it does not override them. […] Truly advanced alien technology might manifest itself by an entirely new form of whole–part interrelationship. And just as quantum weirdness is uncovered only with very special apparatus, so alien technology might go unobserved and unsuspected, because we are not viewing it with the equivalent of… well, a Bose–Einstein condensate beam-splitting interferometer.

However, while we may not completely understand the Universe, there exist certain laws that we can be fairly sure of, notably the second law of thermodynamics and the maximum speed of light. Davies uses these laws to dismiss science fiction, such as a quantum vacuum drive (violates the second law of thermodynamics) and levitation (violates the law of gravitation). To this blogger, this chapter by Davies discusses one of the unsettling things about SETI: its apparent indifference to its existential problems. While astrobiology can rely on our understanding of the biochemistry of terrestrial life (particularly bacteria), SETI is limited to humanity’s machinations. SETI experiments have varying levels of assumptions and most palatable are the parasitic searches focusing on Dysonian SETI. Once cultural assumptions come into play, SETI quickly devolves into fantasy. While a given experiment may be a null result, if it explores a subset of an infinite-dimensional manifold then it is scientifically useless. SETI should proceed but should take caution to limit itself to experiments where a scientific result can say something informative. To this blogger, a reasonable way to search for life would be to start with unintelligent life within our own Solar System, then work together as a scientific community towards extraterrestrial intelligence.

Searching for Humans around White Dwarfs

One of the primary tasks in astrobiology is to detect biomarkers. Lin et al, in a recent paper, argue that industrial pollutants could be used in lieu of biomarkers to detect life on other planets. The unexpected twist in their hypothesis: they propose to observe old white dwarfs. They argue it is possible to look for pollutants from an industrialized society with technology comparable to ours. According to the authors, the ideal pollutant to detect would be specific chlorofluorocarbons (CFCs).

Lin et al begin by motivating their choice of host star. Following previous work by Loeb and Agol, they cite three reasons to favor these stars:

  • white dwarfs have long-lived habitable zones as they are at the end of stellar evolution,
  • the similarity in size of the white dwarf and an Earth-like planet should give the best contrast between the planet’s atmospheric transmission spectrum and the stellar background, and
  • after a few billion years, a white dwarf at the Sun’s effective surface temperature should have a spectrum similar to the Sun, creating a comparable habitable zone, albeit much closer to the star

Lin et al mention that habitable planets could plausibly form debris of the stellar remnant. In short, a white dwarf could host an Earth-like planet at ~0.01 AU. If we further assume there is an anthropogenic civilization on said planet, they could industrialize and produce pollutants. The authors argue the ideal pollutants would be CFC-11 and CFC-14. CFCs have short lifetimes in the atmosphere (at most a few thousand years) and largely produced unnaturally, at least on Earth. There may be volcanic and fumarolic CFCs, but these are appreciably lower in concentration. The estimated time for this measurement would be on the order of day with JWST, which the authors argue could be used to simultaneous detect a spectral edge, be it natural or artificial. The simulations of spectra are shown in Figure 1.

Figure 1. Above are the spectral windows used for detecting CFCs and select molecules used in this paper. The top row shows the combined transmission spectrum. The orange segments are expanded below to highlight where CFCs and other molecules have significant lines. In each zoomed segment, the black represents the contribution from the most significant components of Earth’s atmosphere. Lin et al argue the highlighted regions make good regions to observe for pollutants caused by an Earth-like civilization around a white dwarf.

This blogger is in awe at the assumptions going into this paper. The notion of white dwarfs around planets, while not new, invokes various questions of habitability. If we assume the planet existed before the stellar remnant emerged, how could it survive and retain its orbit? If we assume the planet forms from stellar ejecta, would the metallicity allow for the formation of a rocky planet? “Polluted” white dwarfs do exist and have evidence of debris disks, but as of yet no bona fide planet has been detected around a white dwarf. If we ignore that assumption, the issue of detectability persists and the choice of a cultural signal (a pollutant). CFCs are particularly heavy and would require an observation to probe beneath a significant amount of atmosphere. Furthermore, if in the outer atmosphere, UV radiation would readily destroy CFCs. The required resolution of 3000 is the estimate from JWST documentation but it may be much less at these particular windows. Lin et al assume the civilization must develop like Earth and cause an excess (more than ten times our currently level) of pollutants while refusing to control said emissions. Too many assumptions go into this argument for it to be a viable SETI experiment (i.e. a direct JWST proposal).

Is SETI Interdisciplinary?

Wright views SETI as an interdisciplinary field, albeit one that is fragmented and mired by inconsistent jargon. In a recent paper presented at the SETI Institute Workshop, Wright attempts to organize the terminology and subfields of SETI into a unified framework. He explicitly states:

SETI [is] an interdisciplinary study that includes the humanities and social sciences, and a subfield of astrobiology that focuses on the detection of technosignatures (as opposed to biosignatures). Two major branches of SETI are communication SETI and artifact SETI (although the line between them is not always sharp), and others include METI and the search for “nature plus”.

Above is a comparison of “orthodox” SETI and “Dysonian” SETI.  Wright argues that SETI as a whole is in between both of these extremes. The fact that each extreme focuses at difference frequencies and has different assumptions of advanced technological civilizations (ATC) suggests multi-discipline approach. The table is from Bradbury et. al. 2011.

Wright references the arguments brought by Robert Bradbury et. al. There are two primary extremes in SETI: (i) traditional SETI focusing on intentional messages primarily in the radio and (ii) Dysonian SETI focusing on artifacts and traces of advanced technological civilizations (see Table 1). Bradbury concluded that:

orthodox SETI is not only low probability in terms of success, it is also potentially risky, stunting and scientifically limiting […] We suggest that there is no real scientific reason for such situation. The regrettable condition of SETI is due to excessive conservativeness, inertia of thought, overawe of the “founding fathers,” or some combination of the three. Another, albeit extra-scientific, argument often put forward in informal situations is that the massive pseudoscientific fringe surrounding SETI (“flying saucers” enthusiasts, archaeo-astronauts, and the like) would feel encouraged by relaxing the conservative tenets of the orthodox SETI. […] The proposed and unconventional approach, with its emphasis on the search for the manifestations of ATCs would lose nothing of the advantages of conventional SETI before detection [63], but the gains could be enormous

For Bradbury, to focus on just radio SETI lacks scientific merit and appears to be done out of deference to the founders of SETI. Instead, both orthodox and Dysonian SETI should be viewed as one field requiring knowledge from various other subfields. Wright builds upon Bradbury’s conclusion by attempting to show that SETI is interdisciplinary. He notes that SETI can be performed at multiple wavelengths, such as the optical and near infrared. A lot of the examples provided; exoplanetary science, galactic and stellar astrophysics, time-domain astronomy, and multi-messenger astronomy easily make SETI part of physics and astrophysics. The case for interdisciplinarity becomes more concrete for the social sciences. Wright appears to argue for the need of xenology, using humanity as a logical stepping stone. This is a reasonable step and, while social sciences will inherently carry an anthropocentric view, it does allow for interesting dialogue with social scientists and practitioners of SETI.

Wright argues that for SETI to embrace multiple disciplines, it must standardize the jargon used by practitioners. While some of the terms he mentions are obscure (alien race), others such as “intelligence” and “beacon” have clear implications in what SETI is searching for and how to proceed. This blogger is largely in agreement with Wright. It makes no sense for SETI to be fragmented into many factions as they are all doing something to search for extraterrestrial life. Normalizing the language used is but one step. As mentioned by Bradbury, there still exists some stigma towards Dysonian SETI which hopefully disappears as more searches are performed.

Playing Games with Lasers (Beaming Manhattan into the Void)

Everyone has been in a situation where they need to make themselves conspicuous. Proponents of SETI have often provided novel solutions to ensure an observer would readily identify their planet as one hosting life. The answer can be condensed to a basic principle: do something unnatural at the exact moment someone is observing you. David Kipping, an astronomer at Columbia University, who searches for planets and moons beyond our solar system, believes lasers can be used by ETI to serve as a beacon or mask a planet entirely. In a recent paper, Kipping and a graduate student argue that artificial transit profiles can be feasibly generated using laser emission. Unlike optical SETI, which focuses on pulses of light, Kipping believes the transit can be a useful signal to or cloak from Earth (see Movie 1).

Movie 1. Alex Teachey on Cloaking Planets
One of the co-authors of this paper sets out to describe how lasers could be used to cloak a transit. The timing of this video showed poor foresight (April Fool’s Day….). A secondary video by Alex provides answers to some common questions from YouTubers.

The use of transits in SETI goes back to the pre-Kepler days, when Luc Arnold first proposed distinguishing a transiting mega-structure from a natural body. Cloaking a planet requires many assumptions. Kipping ask us to consider an arbitrarily advanced civilization that discover all “nearby” habitable planets along their ecliptic plane. Kipping assumes the inhabitants would know which of these planets could observe their transits and, through some machinations privy only to ETI, such civilization would decide to prevent detection by these planets using the transit method. Kipping et. al. dismiss a previous suggestion of a mega-structure, arguing a powerful laser would be “technologically more feasible”. After performing a few calculations, Kipping et. al. argue a ~60 MW laser would serve as an optical, “broad-band” cloak and prevent detection from a mission such as Kepler. A laser, while monochromatic, could in theory serve to effectively mask a transit, as shown in Figure 1. Kipping et. al. argue that a laser array on the surface of a planet would be difficult and that instead ETI could place an array of lasers in space (colloquially known as a weapon). The authors aptly refuse to compare either solution. A similar and energetically cheaper alternative would be to use lasers to block out the absorption lines of biosignatures.

Figure 1. The Strange World of David Kipping
Both images are from Kipping et. al. 2016. On the left: Cloaking of a Transit Signal. The top panel shows the unaltered transit for various missions. The middle panel is the power profile of a 600 nm laser array designed to cloak the Earth. The bottom panel shows what an observer would detect. On the right: Using Transits as a Beacon.  The top panel shows the power profile of a laser array designed to broadcast the Earth. The bottom panel shows the transit signature an observer would detect. The laser makes for very unnatural signatures that distinguish it from orbiting planets.

In addition to cloaking, Kipping et. al. briefly discuss signaling via lasers. Broadcasting would be much cheaper, as it would not have to be broadband. The ingress and egress could be altered with lasers as shown in Figure 1. Another possibility, is to use lasers to etch intriguing patterns during the light curve. Kipping has stated:

You can make your transit look strange, have bumps and wiggles, maybe even the New York City skyline—whatever you want.

Savvy extraterrestrial scientists could use a deformed transit as a beacon to announce their existence (see Figure 2). By Kipping’s hypothesis, ETI no longer required planet-size megastructures, such as a rotating triangle or louvres, to produce unnatural transit signatures.

Figure 2. Laser Doodles
Going from top to bottom: (i) An unperturbed transit showing how a star dims slightly when an orbiting planet passes in front of it. (ii) A transit showing different shapes due to a laser array aimed toward an observer. This example shows the New York City skyline. (iii) The ideal beacon would be a square. This is a simple shape that would never occur naturally (yay limb darkening) and would require a laser only at ingress and egress.  Source: David Kipping

The reader is left with many questions and a sense of unease given all the assumptions. The ETI in question is apparently aware of all habitable planets in its ecliptic plane and capable of generating an array of lasers to block its transit. This is an act in vain if said planets use other techniques (i.e. direct imaging or radial velocity) to detect said planet. Kipping et. al. acknowledge this:

Transits are not the only method to discover planets and thus a truly xenophobic civilization may conclude that even a perfect and chromatic transit cloak would be ultimately defeated by observation of the planet using radial velocities. In this sense, the biocloak is perhaps the most effective strategy since certainly the transit and radial velocity measurements would appear compatible. However, even here, direct imaging would reveal a strong discrepancy in terms of the atmospheric interpretation and thus overcome the cloak.

A large part of this paper was to discuss how a transit could be cloaked, only to have that entire hypothesis appear to be an act in vain. The discussion on broadcasting with a strange transit signature is not fundamentally new. This blogger is left pondering the purpose of this paper. The authors themselves have dismissed the efficacy of cloaking and suggest we search for strange transits, something proposed by Arnold a decade earlier. Even if one were to assume cloaking to be efficient, SETI has predominantly concerned itself with civilizations indifferent to outside observers. After all, one could always invoke any arbitrary set of conditions or technology that would make a civilization impossible to detect. While the method of using lasers is novel, the rest of the paper reminds astronomers to search for strange transit signatures. Believe this requires strong priors and an indifference to all the assumptions. Kipping himself expects detections “on the order of a few dozen” and this blogger wishes him the best in his future endeavors.

Masers are the Future

Cocconi and Morrison initially proposed interstellar communication using radio waves, particularly near the hyperfine transition of hydrogen. The first SETI observations, conducted by Frank Drake, followed this suggestion of where to look. The focus in the microwave was a result of technological limitations, as observations at other frequencies were unimaginable when Cocconi and Morrison initially presented their work. With the discover of the maser in the 1950s, a new vector for communication became available. The authors postulated that “maser oscillators and other appropriate apparatus in or near the optical region [will] allow detectable light signals to be beamed between planets of two stars separated by a number of light years”. The creation of the laser in 1960, a more practical device than a maser, served as further justification for this claim.

Townes and Schwartz note the physics behind the maser was first described by Einstein. There was no theoretical deficit precluding its discovery or delaying development. The authors use this to argue that there may exist an extraterrestrial society comparable to Earth that discovered and developed masers before radio waves. They boldly state:

We propose to examine the possibility of broadcasting an optical beam from a planet associated with a star some few or some tens of light-years away at sufficient power-levels to establish communications with the Earth. There is some chance that such broadcasts from another society approximately as advanced as we are could be adequately detected by present telescopes and spectrographs […]

A maser, much like its optical counterpart, could theoretically operate continuously at high power and would be almost monochromatic. Townes and Schwartz note the limit to producing an ideal maser would be the technological problems in mirror accuracy and control of any optical distortions. They considered two masers (1) one energetic maser and (2) twenty-five masers pointing in the same direction and specified two criteria for the detectability of either maser:

  • it must produce enough photons per unit area at the receiver to be detectable with a lens of practical size and in a reasonable time and
  • it must be distinguishable from the background stellar light.

They argued that the intensity of radiation from the group of masers would produce a beam of high intensity capable of being observed by the naked eye or binoculars out to 0.1 or 0.4 light years, respectively. A larger telescope of long integration would be required for masers further than 10 light years. The authors note that, from the work of Cocconi and Morrison, there were ten Sun-like stars within a distance of 10 light years, making masers very applicable to SETI. Spectra would be another useful diagnostic for a maser. A grating spectrograph in the 1960s could have resolved the energetic maser as a signal equal to the stellar background. Noting this, Townes and Schwartz propose that “[a] spectral line sought can be expected to be exceptionally narrow, at an abnormal frequency for the type of star in question, and varying in intensity [o]bservation of any of these characteristics should lead to closer examination” of an object.

In less than a decade after discovery, masers were already being considered for SETI. The advantages include the coherence of radiation over a very large aperture and the theoretical possibility of obtaining coherence among several maser sources. Given that nay plausible atmosphere would prevent emission of masers, the authors propose utilizing a “very high-altitude balloon, a space platform, or natural Moon”. Only two years passed after Cocconi and Morrison published and people began considering where to look. This is an on-going discussion, but the authors correctly argue that charged particles would be deflected while UV and IR emission would be absorbed by an atmosphere. This blogger considers this to be an important discussion. When this was originally published, SETI was still in its infancy and the authors emphasized the need to consider other wavelengths before all of SETI focused on microwaves. While the development of masers may have stymied after the discovery of the more practical laser, optical SETI now exists. Recent progress in masers (see Movie 1) suggest their applicability will soon increase. Perhaps the masers of the future will become useful for SETI as Schwartz and Townes initially proposed.

Movie 1. Mainstream Masers Coming Soon™
Laser are everywhere, but masers came first! They are like lasers but in the microwave. This video shows the latest applicability of masers. Who knows, perhaps the suggestion by Schwartz and Townes to use masers for communication is not too far off.

The Gangrenous Limb of Science: Hard Science Fiction

***It should be stated the author is not a fan of science fiction in general. But there is nothing inherently wrong with the genre until scientists begin to use fiction to address scientific problems***

Is it fiction, science, or an unholy amalgam of both? That is the question this blogger tried to address when reading “Gravity’s whispers”. Gregory Benford is both an astrophysicist and a writer of hard science fiction. Hard science fiction attempts to lead the reader to a fictitious world with an emphasis on scientific accuracy. On his Amazon page, it states:

Often called hard science fiction, Benford’s stories take physics into inspired realms. What would happen if cryonics worked and people, frozen, were awoken 50 years in the future? What might we encounter in other dimensions? How about sending messages across time? And finding aliens in our midst? The questions that physics and scientists ask, Benford’s imagination explores. With the re-release of some of his earlier works and the new release of current stories and novels, Benford takes the lead in creating science fiction that intrigues and amuses us while also pushing us to think.

This piece hardly makes one think about the science and more about the literary elements forgotten in science fiction. The story begins with a date and a quote popularized by Voltaire: perfection is the enemy of good. It should be noted this piece is neither. An unnamed scientist (this is left unclear, for all we know it could be part of the janitorial staff at the VLA) has tried to decipher a signal received from their date, Sam the Slow. The mysterious protagonist purportedly spent a day trying to decipher a noisy pattern. Their work paid off and revealed “a string of numbers, […] the zeroes of the Riemann zeta function”. Some exposition later, the reader learns Sam is a scientist working on LIGO and this first gravitational wave detection, thought to be a neutron star crust vibration, actual contains a message. Real talk follows:

‘What? A tunable gravitational wave with a signal? That’s im—’ ‘—possible, I know. Unless you can sling around neutron stars and make them sing in code’

The progenitors of the signal even provide a proof for one of the unsolved problems in mathematics. There is talk of a Nobel prize and relief in that humanity cannot answer the SETI signal.

There were various moments of drivel, notably in the discussion of romance between both parties. It neither adds to the plot nor to the purported science. What should have been discussed more was the signal processing. To this blogger, the mysterious protagonists might as well be ETI. They were somehow able to decipher a gravitational wave chirp to reveal a solution to a Millennium Prize Problem. These individuals will apparently win a Nobel for the detection of SETI and a Millennium Prize. Sam notes “the rest of them”, presumably scientists, would laugh at this assertion and this serves to emphasize the delicate nature of the topic.

The actual content of the message should not be too important as it could have been random prime numbers, albeit the discussion of the Riemann hypothesis gives ETI high intelligence. Greater scientific accuracy could have been invoked by using eLISA instead of LIGO and positioning the scientsits somewhere other than the VLA. This particular piece was neither amusing nor particularly thought provoking. The only moment of connection between the reader and scientists would have been at the end (not because the story completed…) with the relief that humanity cannot contact this extremely intelligent form of life. This blogger thinks writings such as this are dubious at best. It is the height of folly to presume scientific accuracy on completely fictitious topics, and melding the two somehow gives disappointment a tangible form.

SETI at Different Wavelengths

Charles H. Townes, the inventor of the maser and laser, wrote a paper in 1983 to discuss the appropriate wavelength for the search for extraterrestrial intelligence (SETI). He argued that, while SETI developed, it was important to consider which wavelengths to conduct searches. Beginning with Drake’s Project Ozma, most SETI experiments have used the radio region of the electromagnetic spectrum with particular emphasis on the water hole. With the discovery of masers and lasers, it was possible to consider using them for interstellar communications at optical wavelengths. Schwartz and Townes in a 1961 letter first presented this idea of using masers to communicate over long distances, assuming we used a narrow-band receiver. In this article they proclaimed:

We propose to examine the possibility of broadcasting an optical beam from a planet associated with a star some few or some tens of light-years away at sufficient power-levels to establish communications with the Earth. There is some chance that such broadcasts from another society approximately as advanced as we are could be adequately detected by present telescopes and spectrographs, and appropriate techniques now available for detection will be discussed. Communication between planets within our own stellar system by beams from optical masers appears a fortiori quite practical.

They concluded “the frequency of the hydrogen line in the micro-wave region is not the only reasonable place at which to search for possible interstellar communications, and […] the optical region also seems a logical one”. This paper can largely be viewed as a continuation of his initial work.

Townes begins by motivating SETI at other wavelengths. An extensive search focusing on one regime in the electromagnetic spectrum would be a large endeavor and potentially a waste of resources. The communication capabilities of ETI were assumed to be analogous to our capabilities. The principals for SETI are described via various strategic questions and under the assumption ETI wishes to minimize costs of any technology they use. The first question addressed is the nature of the signal, primarily if ETI signals would be isotropic or directive. It is preferred that a civilization broadcast narrow band. Townes uses the excessive power an isotropic signal would require (9 ordered of magnitude more) to suggest ETI would favor sending a beam. Other assumptions regarding ETI and its capabilities:

  • regarding power sources, there is no necessary choice as a function of wavelength from the radio region down at least into the ultraviolet,
  • there are detectors of sensitivity close to the ultimate limit dictated by the quantum properties of radiation over the whole range of wavelengths, and
  • if needed, the use of space for the beacons is to be expected.

Townes consider numerical evaluations of the signal-to-noise ratio (SNR) for different wavelengths. One potential observation scheme involves using longer wavelengths with linear detection of all wavelengths and a constant antenna area but solid angles corresponding to the diffraction limit only for wavelengths >1 cm. The other observation scheme involves short wavelengths with a quantum counting detector and an antenna with a fixed diameter for long wavelengths down to 1 cm and then decreasing linearly in size to 10 m in the infrared.

These were but two examples discussed. Townes concludes that, depending on the assumptions, other regions, such as the infrared, should be considered. This was a marked departure from what was initially proposed by Cocconi and Morrison. While Townes initial suggest of using the infrared may not be used today, the discussion regarding where to look is still ongoing. Experiments in optical SETI have since been conducted (e.g. Reines & March, 2002), Laser SETI is a thing (see Movie 1), and it optical SETI is one of the projects of the SETI Institute. Recent papers have scrutinized both the wavelength of photons and even the nature of the particle observed by SETI. It may have taken over forty years since the first publication from Townes discussing masers, but at least proponents of SETI are no longer latching onto the microwave.

Movie 1. Laser SETI Wants Your Money
Laser SETI is an example of the types of searches Townes proposed – something not tied to the microwave region. The optimal wavelength to observe is an important discussion that is still ongoing.

So you find aliens, then what?

The SETI Protocols were conceived in the 1980s as procedures for individuals or organizations to follow while performing radio searches for extraterrestrial intelligence. A subset of the protocols, the “Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence”, provides the guidelines that should be followed after the detection of extraterrestrial intelligence. It was initially adopted in 1989 and revised in 2010 (albeit, the SETI Institute only references the old protocols). As stated in the cover letter, the protocols were adopted by various institutions including:

the Board of Trustees of the Academy and also by the Board of Directors of the International Institute of Space Law […] it was endorsed by the Committee on Space Research, by the International Astronomical Union, by the members of Commission J of the Union Radio Scientifique Internationale, and by the International Astronautical Federation

This marked the first attempt to address the concern of what to do if SETI made an unambiguous detection of extraterrestrial intelligence. Gertz states, in his recent discussion of SETI protocols, the principles from the original protocol can be distilled to three broad tenets:

  1. SETI should be conducted transparently;
  2. a detection should be followed by observations and adhere to rigorous confirmatory procedures; and
  3. all parties must refrain from transmitting a response without authorization from a broadly representative body, such as the Security Council of the United Nations.

The revised protocol states SETI searches should be “conducted transparently, and its practitioners [may] present reports on activities and results in public and professional fora [and] be responsive to news organizations and other public communications media about their work”. This explicitly addresses the prevalence of the internet and social media in sharing information and fomenting misinformation. It is an attempt to mitigate the hijacking of the scientific narrative behind any SETI search. The other addition discusses how to handle evidence and confirm a detection. It makes a direct reference to the Rio Scale (SETI-ists have updated this, paper in preparation). The Rio Scale was developed as a suitable tool for assessing the plausibility of detection signal and gauge the impact such an announcement would have on the public. While the Rio Scale may be under debate (one of the original proponents of the Rio Scale now favors the London Scale and there are other blogs debating its use), it attempts to give scientists a tool to mitigate the subjective nature regarding plausibility. As NASA no longer funds SETI, the primary purpose of this protocol is to ensure the detection is real and mitigate misinformation.

The protocols are not perfect (see Tarter’s take in Movie 1) and have come under criticism. Some have argued social media have made the protocols useless. Others have sensationalized the topic. Gertz has questioned the feasibility of enforcement, noting that while “Western SETI scientists” laws protecting them, it might not be the case elsewhere. Gertz has a nihilistic view on treaties with no legal reparations against individuals or entities who do not adhere to the protocol. He contemplates the need to restrict access to information and would like to see the legal provisions backing future SETI protocols and a complete ban of METI. He is also unaware that publications mentioning restricted access to detections only fuel the conspiracy theorists that the government is trying to cover-up the existence of alien life. Gertz ignores the fact that his view of the protocols appears counterintuitive to his interest in SETI. If one truly does believe SETI/METI pose an imminent danger and warrant militant regulation, then why should anyone do SETI? This blogger views both SETI/METI as benign activities that can improve their scientific standing if the protocols are followed. If not, the age of social media will most likely make a spectacle of any detections and render moot what little credibility SETI/METI. The protocols are still lacking and should be revised to explicitly address the dangers of social media, but the attempt to maximize transparency is important in a field sullied with conspiracies, dubious claims, and distorted facts.

Movie 1. Jill Tarter on Post-detection Protocols
If the SETI Institute detects a signal from extraterrestrial life, what happens next? SETI director Jill Tarter explains the protocol for such a situation. She makes a passing reference to the protocols discussed in this blog.

Humanity’s Problem Child: The Internet

Before we dissect the recent craze over aliens in the news, it is important to understand there exist strange phenomena that have not been properly explained. Such events require scrutiny and the application of the scientific method to validate. Lee Billings recently published an article in Scientific American discussing sensational events in the search for extraterrestrial intelligence (SETI) and serves to caution the reader about spurious conclusions with specious data. In the article, Billings has a few sentences that capture the sentiments of this blogger:

Far from being close-minded killjoys, most scientists in the “never aliens” camp desperately want to be convinced otherwise. Their default skeptical stance is a prophylactic against the wiles of wishful thinking, a dare to true believers to provide extraordinary evidence in support of extraordinary claims. What is really extraordinary, the skeptics say, is not so much the possibility of extraterrestrial intelligence but rather the notion that its existence nearby or visitation of Earth could be something easily unnoticed or overlooked. If aliens are out there—or even right here—in abundance, particularly ones wildly advanced beyond our state, why would incontrovertible proof of that reality be so annoyingly elusive?

This is especially true in the age of social media where it is easy to scour the underbelly of the internet for a place to validate any claim. For proponents of SETI, who wish to see this field fully embraced by science, any publications and announcements must be well managed. The first topic Billings discusses is KIC 8462852, the star at the center of an “alien megastructure” theory the media latched onto (see Movie 1). The scientists involved began a successful Kickstarter project to raise funds for observations which ultimately revealed the dips most likely due to clouds of submicron-scale dust. This star was first published in 2015 and the possibility of alien megastructures, inadvertently attributed to Jason Wright, was allowed to gain much traction despite its low probability. Wright states that the unwanted sensationalism lured astronomers to study this object “precisely because all the ‘aliens’ talk annoyed them, and they wanted to find a natural explanation”. The second example was of ‘Oumuamua, which was speculated to be a spaceship but later confirmed to be the first detected interstellar asteroid. Billings uses these to show that the media coverage, while perhaps hysterical, was able to mitigate much damage to SETI due to careful guiding of the narrative by the astronomy community.

Movie 1. Alien Megastructures (KIC 8462852)
Nat Geo describes the various scenarios for alien megastructures that have been considered for Tabby’s star.
Movie 2. The Truth Twitch of Conspiracies
Roger is hosting Conspiracy Con for those individuals who want the “truth”. Unfortunately, in the real world conspiracy conventions exist and people believe the government is intentionally hiding information about alien life.

Billings then dives into the lion’s den – unidentified flying objects (UFOs). Conspiracy theories regarding UFOs are rampant and even make cameos on shows (see Movie 2). In fact, conspiracies themselves have long since gained traction on the internet because of the wealth of data on the web itself allows people to draw links between anything (see Movie 3). This particular story was recently published by the New York Times (the Times), a reputable newspaper, and infused ufology with unneeded attention. The Times discussed a formerly classified program run by the Department of Defense to study reports from the armed services about encounters with UFOs. The program was officially canceled in 2012 and included videos of separate UFO encounters (see Movie 4). This article generated over one thousand comments ranging from support to criticism (one scoffed at money going into looking at UFOs but little to no money going into climate change). Perhaps the most pernicious things are the following points a general reader may take from the article, as pointed out by Scientific American:

  1. many high-ranking people in the federal government believe aliens have visited planet Earth;
  2. military pilots have recorded videos of UFOs with capabilities that seem to outstrip all known human aircraft, changing direction and accelerating in ways no fighter jet or helicopter could ever accomplish; and
  3. in a group of buildings in Las Vegas, the government stockpiles alloys and other materials believed to be associated with UFOs.
Movie 3. The Double-Edge of the Internet
The Internet can fuel paranoid thinking. In this video, example include 9/11, lizard people, and aliens. It can be dangerous for science to let conspiracies gain and hold traction, such as in the Times article about UFOs.
Movie 4. The Pentagon and UFOs
Above is a video the Times released in its article showing the purported UFOs. These objects, while unexplained, should not readily be attributed to aliens. They, like all UFOs, must be analyzed from a scientific perspective. The videos from the Times have served to foment more conspiracy theories.

This is pouring lighter fluid on conspiracy theories. To a layperson, this may seem as concrete evidence UFOs exist. The government has spent millions to search this phenomenon and has been secretive in releasing information, only fomenting ideas that the government knows “the truth” but is hiding it. The release was so sensational it wormed its way to the OVNI section on Univision and other reputable news sources. The rate at which this spread caused immediate backlash with some trying to make sense of the information and to mitigate conspiracies. Billings himself argues one should be careful with these extraordinary claims showing a dearth of high-quality evidence. Aliens and UFOs should never be the first conclusion to unexplained phenomena until all other natural phenomena can be thoroughly excluded. A quote from Bruce Macintosh makes a great point on UFOs:

UFO detections have remained marginal for decades; they’ve just gone from being blurry shapes on film cameras to blurry shapes on the digital infrared sensors of fighter jet gun cameras. This, in spite of the fact that the world’s total imaging capacity has expanded by several orders of magnitude in the past 20 years.

Movie 5. Scientist Fending off Conspiracies
Above is a video from the Washington Post where David Morrison, from the NASA Ames Research Center, strives to debunk the conspiracy theory of Nibiru. Even this blogger was asked questions about this object last year while apartment hunting. The person asking was under the impression I was hiding information. It is important for scientists to publicly fight disinformation!

This blogger agrees that to assume aliens are the answer to UFOs and adamantly cling to that conclusion is not science and warrants intense scrutiny from scientists. Astronomy itself is no stranger to conspiracy theories about many things, such as Armageddon. It is incumbent on scientists, particularly proponents of SETI, to get their narratives out to the public and fend off conspiracies (see Movie 5). This may place a heavy burden on scientists, but it is necessary to fend of disinformation and ridicule that has plagued SETI. While we know UFOs exist, even as chicken coops (see Movie 6), it is important to be able to draw the line between science and fiction that can set back research endeavors.

Movie 6. The Real UFOs
Real UFOs have chickens! Above is a video showing modifications done to a chicken coop to add lights and sounds in the name of sensationalism.

Bacteria, the Bane of SETI

Jason Wright, in a recent post on Scientific American, argues that NASA should fund the search for extraterrestrial intelligence (SETI) as part of its astrobiology program. Since 1993, SETI has not been funded by NASA. However, the recent Release of Annual Research Opportunities in Space and Earth Sciences 2018 (ROSES–2018) Omnibus NASA Research Announcement has conflicting remarks regarding SETI research. Under the “Evolution of Advanced Life”, it states “[p]roposals aimed at identification and characterization of signals and/or properties of extrasolar planets that may harbor intelligent life are not solicited at this time” while under “Biosignatures and Life Elsewhere” it states “… research focused on understanding or characterizing nonradio ‘technosignatures’ from extrasolar planets that may harbor intelligent life are included in this area”. NASA itself appears to be unsure about SETI. Wright, in an attempt to bolster why SETI should be considered for funding, remarks:

… there is no a priori reason to believe that biosignatures should be easier to detect than these technosignatures. Indeed, intelligent, spacefaring life might spread throughout the galaxy, and therefore be far more ubiquitous than planets that have only microbes. Life might be much easier to find than the NASA strategy assumes. Indeed, it has been noted cynically, but not untruthfully, that NASA eagerly spends billions of dollars to search for “stupid” life passively waiting to be found, but will spend almost nothing to look for the intelligent life that might, after all, be trying to get our attention. This is especially strange since the discovery of intelligent life would be a much more profound and important scientific discovery than even, say, signs of photosynthesis on the nearest exoplanet to the solar system, Proxima b

In many ways, this simplistic view on life hinders progress for SETI. Only a small number of all microbial species have been described. There are estimates suggesting that more than 1 trillion (1012) species of bacteria, archaea and microscopic fungi exist on Earth, orders of magnitude more than eukaryotes (some have argued these are a few million), particularly any “intelligent life”. There are perhaps orders of magnitude more prokaryotes in space which have yet to be detected. NASA has considered the search for biomarkers as an indirect detection of life and has also considered the impact of bacteria. Furthermore, on Earth we know bacteria (i) predate complex, intelligent life, (ii) played an important role in altering the composition of the atmosphere, and (iii) have left stromatolites and other geochemical features as the oldest record of life on Earth. In short, if we cannot find traces of the most common form of life, a form incapable of masking its signature from us, then how can we expect to find extraterrestrial intelligence?

Rennie and Reading-Ikkanda, in a recent publication on Quanta Magazine, show the complexity of simple prokaryotes and, while not a SETI article, make the case that bacteria are dynamic organisms capable of adapting to their environment. The diversity of these organisms is shown in Figure 1. The authors first mention the discussing the ability of bacterial colonies to synchronize and swarm, much like flocks of birds or schools of fish. Under the microscope, the ability for precise movement is surprising, given the lack of differentiation in the organism (see Movie 1). Bacteria, particularly slime mold, are able to crawl around in search for a nutrient-rich environment with controlled secretion of chemicals to ensure (i) they do not explore a nutrient-deficient region and (ii) they grow asymmetrically. Biofilms, compact societies of bacteria, are able to grow in three dimensions and even on non-solid surfaces. In dense bacterial colonies, there is something analogous to differentiation where bacteria on the inside anchor in place, bacteria at the edges of the biofilm divide for growth, while others in the middle release spores for new colonization.

Figure 1. The Joys of Bacteria
Going counterclockwise from top left: (i) Physarum polycephalum explores an area and leaves behind a chemical trail if the region is nutrient deficient. (ii) Bacteria do not need a solid surface for growth. This B. subtilis culture grows by forming a floating biofilm across the air-liquid interface in a beaker. (iii) Spiral migration is a behavior favored by the soil bacterium Bacillus mycoides. Communities of these cells expand by forming long filaments of cells that coil either clockwise or counterclockwise. (iv) In this powdery colony of Streptomyces coelicolor, the pigmentation comes from actinorhodin, a molecule with antibacterial effects. Biofilms may use bioactive pigments as signals for controlling the behaviors of other microorganisms in their shared environment. Source: Quanta Magazine

Movie 1: Synchronized motility in bacteria. In a colony of E. coli cells, two silicone oil tracers exhibit synchronized loops. Source: Quanta Magazine.

While the bacteria covered in this article require humidity and warm temperatures around 30°C, this is not the requirement for all prokaryotes. In the 1980s and 1990s, scientists began to discover that bacteria were robust organisms, capable of surviving in extreme environments not amenable to most eukaryotes. These so called extremophiles are capable of living in regions that would be otherwise inhospitable to life. Bacterial spores are also fairly robust and it has been theorized that life on other planets in the Solar System could be seeded from extremophiles ejected from Earth or Mars. Table 1 shows a few examples of extremophiles from the NASA Astrobiology Strategy. There is also genetic evidence that the last universal common ancestor is a thermophile (a subset of extremophiles).

The search for life should begin with the most common organisms known to us, bacteria. If scientists can detect extraterrestrial bacteria (e.g. on other bodies in the Solar System), the case for SETI would be much stronger. If bacteria could exist elsewhere, then presumably they could be the precursors of more complex life. This could then be used as a bolster to SETI’s claim – if there exist simple organisms outside of Earth, why should anything prevent “intelligent life” from evolving? As it stands now, SETI’s focus on “intelligent” non-microbial life seems specious at best. The arguments presented by Wright do little to inform the reader why “stupid life” should be more difficult to detect than tenuous technosignatures. SETI itself is not informed by biology or chemistry and it seems unclear to this blogger why it should even be considered astrobiology as opposed to astronomy. Until SETI can motivate why one should search for rare life when the most common form of life appears non-existent elsewhere, it will remain a commensal offshoot to astronomy.

Table 1. Characteristics of known extremophiles on Earth. Source: NASA Astrobiology Strategy