Back in 2015, Stephen Colbert hosted Neil DeGrasse Tyson and Seth MacFarlane on his show. Stephen brought up Tabby’s star, explaining that one of the explanations for the drastic dips, although improbable, was that an alien megastructure could be orbiting the star. Although I would have preferred he listed the other possible explanations, I suppose I’m okay with how he introduced the topic because he mentioned that the likelihood of it being aliens was low.
It’s the next statement that bothers me. Seth MacFarlane chimes in with “Ya, I read that on Buzzfeed, so it must be true” (sarcastically), but this annoys me! Since the 2000’s with Wikipedia, there has been this sarcastic statement going around of “well I read it on the internet, so it must be true.” In extension to this, outlets such as Buzzfeed have started developing reputations as only there for their fans, publishing anything their fans might like, regardless of whether it was true or not (I’m saying this is becoming their reputation, not that they don’t fact check because honestly I don’t know). With all this, if Buzzfeed posts something about an alien megastructure found by astronomers, it will either reflect poorly on them or on astronomers.
Unfortunately, there is no way to get around the fact that the general population automatically calls BS to anything about aliens. As shown in this clip from Late Night, it is near impossible to have a legitimate discussion about SETI without astronomers rolling their eyes and everyone else just thinking it “fake news” (another popular statement these days). Neil responds to this statement with an exasperated expression and the statement “Just because you don’t understand something, doesn’t mean it’s aliens.” Well you know what, Neil?? No one said it *was* aliens! It was proposed as a solution, along with a ton of other things, but it *is* a solution to this anomalous data. The media picked up on that one little thing, and went crazy with it. Neil is right, in general, but I think it is important to remember that aliens are an explanation to different things we don’t understand, and while all other explanations should always be explored first (and with more fervor), aliens should not be removed as a solution just because sci-fi has trained us all to believe this silly and impractical.
In an interesting (and refreshing for my workload) change of pace, we have been assigned a video in addition to the normal literature readings for this week. See below.
In the clip, we see Neil deGrasse Tyson (NDT) and Stephen Colbert (SC) discussing the discovery of Tabby’s Star, a mature star found by Kepler that exhibits non-periodic dips in brightness, some of which are ~20% of the total brightness. The star also appears to be dimming gradually over time. Currently, we are unsure what is causing these phenomena.
Upon first watching of the clip, I was a little disconcerted but was unable to figure out why.
The first thing I noticed was NDT’s comment on the Kepler mission. Kepler was launched “to find Earth-like planets orbiting Sun-like stars”. Sounds good so far. “And there is a catalog of nearly 2000 of them now”. Aaaaand that is misleading as heck. I feel like I can confidently claim that a lot of people would interpret that as “We have found over 2000 Earth-like planets around Sun-like stars” instead of the actual fact that while Kepler was proposed to do one thing, it ended up finding exoplanets of all sorts (with a natural bias towards larger and smaller period planets). While this might be viewed as a nitpick, science communicators like NDT are often criticized heavily for misleading comments and errors in their appearances, and, it could be argued, rightfully so. Scientific communicators are the filters that bring the complicated and nuanced ideas (both new and old) within a field to a significant portion is the public. In this way, they have an incredible influence on the public perception of science. A power that is quite enticing (to me anyway). A good science communicator can drive public interest to a field (or science in general) for decades (eg. Carl Sagan, Bill Nye, Jane Goodall, and Steve Irwin are a few I could think of). It is important that they be correct and precise as often as possible. I understand when they, as fellow humans, make mistakes (I can’t even type a line of this post without having to hit the backspace key), but they have to be very careful because, to many, their word is gospel. They are the experts, after all. If you can’t trust them to get things right, who can you trust? It is hard in that people who become popular end up being asked to comment on broader and broader topics. As smart as they are, no one can be expected to have infallible knowledge of astronomy, physics, biology, climate science, anthropology, and every other topic of scientific inquiry.
The comment that started this whole line of thought could’ve been worse, but it reminded me of this topic.
The second bit that irritated me slightly was how SC makes his joke about how Tabby’s Star is definitely a ringworld (he has a picture!), and interrupts NDT when he tries to respond. While I understand that SC has a job to do and is making a joke (sidenote: I chuckled), I am always uncomfortable watching something like this happening. Just the fact that NDT is there makes it seem like the scientific community as a whole stands by this opinion at some level (“Yeah, I was watching SC last night, and NDT was on and they said we found alien megastructures around a star!” (not trying to create a strawman, but to illustrate a possible outcome)). This type of thing can make the scientific community seem less credible and can impact the subconscious way that people view scientists and research. Now, I haven’t seen the full show this is from so I don’t know if they discuss it later afterward, but at least with this level of context, it is frustrating to see.
I mean, it is also just a 2-minute segment from a late-night comedy show. Nothing in this clip is particularly awful. Nonetheless, it may act as a barometer of current societal trends and give insight to where these trends might take us.
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.
The authors of Rennie et al. (2017) paper think microbes are not so different from robots designed artificially with the capability of responding to the surrounding environment.
The authors first argue that the slime mold has a sense of intelligence by advancing towards in the direction with more nutrients by pumping cytoplasm in that direction. Additionally, slime mold has the ability of leaving chemical trails which reminds it places not worth visiting.
Further, the authors discuss the intelligence of bacteria, especially biofilms. First, they argue that biofilms have sophisticated structures which allow them to absorb nutrients nearby as much as possible. Moreover, the cells in biofilms have different functions depending on the location of the cells in the biofilms. Similar to slime mold, biofilms have the capability of moving towards locations with more nutrients by secreting materials which help them move more energetically and more rapidly.
Additionally, biofilms have different spiral migration pattern depending on their genes. Biofilms also are intolerant of other strains so they develop boundaries between each other when forming.
Wright (2017) explains that that searches for ETI should include searches within the solar system. He argues that it is a good place to look (either for extant or extinct life), because it is near the only place we for sure know harbours life, Earth. He argues that life could have arisen on other bodies in the solar system (namely Venus, Mars, maybe the moon, the icy moons, and possibly asteroids or KBOs), and mentions that it is even possible that a prior species on Earth arose before humans that was intelligent.
I agree with many points in this paper. I believe that SETI should include solar system searches, especially because of the data we already have for many of the bodies. This links back to the argument by Davies and Wagner (2013) that SETI should be done not based on the possibility of discovery, but based on the time and effort the search would take. Solar system searches take remarkably less time since the objects are closer to us.
Wright points out that Venus could have been a good host of life before it lost all of its water and went runaway greenhouse. Unfortunately, Venus has such a young surface from its volcanic flows that any evidence older than a couple hundred million years would be completely erased, and any evidence prior would likely be erased too. Mars is a decent target since it was probably wet once and capable of hosting life before it lost almost all of its atmosphere, but weathering on its surface is decent and any artifacts would probably be covered by now. Other objects in the solar system and their associated datasets should be searched for technosignatures though.
That being said, there is a point in Wright’s paper that I very much disagree with, and that is the possibility of an intelligent species before humans. While I will grant that the fossil record is horrifically incomplete, one flaw I find in this suggestion is the need for oxygen. Our planet was very anoxic before about 500 million years ago, and the rise of life is highly correlated with rising oxygen levels. While any life could have been anoxic, most astrobiologists search for life that requires oxygen since it is the only life we know. Wright is calling for an analysis of ancient facies in search for technosignatures; I think this exceeds the “low cost” criteria, especially given that a successful search requires the assumption that any life inferred did not require oxygen. On top of that, although the fossil record is lacking, there is no indication of any line of evolution that was anoxic, nor evidence of a rise in intelligence that went extinct (unless we include intelligent dinosaurs?). This suggestion just seems fanciful to me; although it would be kind of neat, we have absolutely no reason at all to believe that such a species arose, no evidence of anything that could destroy such a species (except maybe KT?), and any intelligent life would need to be anoxic and would defy our current understanding of life.
I don’t really know why you would want to build a city on a Kuiper Belt Object (KBO), but then again, I’m not an alien.
We thought the aliens were watching I Love Lucy, but maybe they’re watching Cowboy Bebop instead
Loeb and Turner (2012) make an argument that artificial lighting could be a good universal “lamppost”: something that all technologically advanced species would do so as not to be subject to the whims of a diurnal cycle. I can think of quite a few problems with that: a species that evolved in a sub-surface ocean, species on tidally-locked worlds that never had a diurnal cycle, the ever-popular “post-biological life”, etc.
But okay, sure, let’s say everyone needs street-lamps. With current technology, we would be able to detect artificial lighting (on the scale of a large terrestrial city) on KBOs in our own solar system. Regardless of plausibility, that’s pretty cool!
That part is in bold because it’s obviously the way this paper came about. I don’t think there are any good arguments for why KBOs are the best place to search for extraterrestrial life. I’m open to being proven wrong, but the paper reads as a fun thought experiment based on a new technological capability rather than any serious suggestion for how humanity can find another intelligent species.
The authors discuss a characteristic “flux-distance signature” that an artificially illuminated object would have. Based on a double r^2 relation (one in sunlight reaching the object, one for the backscattered light), a KBO that’s just reflecting naturally due to its albedo should increase in brightness by a factor of r^4 as it comes closer to the sun. Meanwhile, an object dominated by artificial illumination would only increase by r^2 as its source of luminosity approaches. Thus, if we notice any objects with this r^2 relation, we should really take note because that would be really weird.
The authors also discuss caveats and confounders of this idea (phase angles, outgassing, albedo variations, rotation, binary companions…), but indicate that all of these should be periodic with the exception of outgassing and should average out over years of observation. They also briefly talk about how this idea could be applied to exoplanets (with phase curves and such), but it doesn’t seem like the the technology is there yet.
This definitely felt to me like a good example of Davies and Wagner’s proposal of cost before plausibility in SETI work (discussed in a previous post). They outline the logic behind the method pretty well, but if they were actually interested in the results instead of the theory they should’ve looked more into which pre-existing datasets could be used to attempt this kind of work. Because if someone* was interested in actually testing this idea, and not waiting for LSST etc., it would be nice to be able to hit the ground running on it.
As I indicated in my first sentence, I don’t really see a reason why there should be artificial lights on a KBO. They’re cold, they’re small, they don’t have thick atmospheres, they have no access to non-Kuiper Belt resources (what, you wanted something other than ice and dust?), etc. That said, if the search is easy to do and we can clear out some parameter space… perhaps it’s worthwhile.
In this article by Loeb and Turner (2012), they propose the search for artificial illumination around Kuiper Belt objects on the outskirts of the Solar System. This would be a search for technologically advanced ET in our vicinity.
As one can see when flying at night during take off or descent into a big city, humans like to lengthen the duration of the ‘daylight’ using artificial light sources of lighting. Since our circadian rhythms have evolved to sleep when the Sun goes down, our eyes are not sensitive enough in low light conditions (night). Therefore, we try to illuminate our surroundings using fire and electricity for us to extend the hours we can work / recreate (or do anything), apart from sleeping. Since we as a species are very wasteful with little to no collective foresight, most of our sources of illumination are such that a huge fraction of the light they produce is wasted and radiated out into space. Below is an image which shows what the night sky looks like over various points on the Earth’s surface. This is an image created by piecing together numerous snapshots by NASA.
Earth at night. Credit: NASA
In this article, the authors propose a search for similar lighting around Kuiper belt objects (KBOs). Why KBOs? Perhaps since we have already looked at the moons of Jupiter and Saturn to rule out such ‘city’ sized illumination. However, I do not see the utility of such a search.
A KBO at about 50 AU would experience about 0.04% the Solar Flux we receive on Earth. Would sunlight really be an efficient source of energy for a civilization there? What are the alternatives? Chemical or fossil energy also relies on a primary energy source which is Sun in the Earth’s case. An advanced civilization cannot directly start using nuclear energy. Therefore, barring solar energy, there is no energy source that a primitive life form can utilize and evolve along. Even if one argues that the amount of sunlight is sufficient for species to thrive (like deep in the ocean) or caves on Earth, then the question arises can it sustain an intelligent civilization like humanity with a power hungry ‘brain’?
Moving on, if we argue that evolution is the mode by which life forms and transforms into intelligent life; then why will a ET civilization need bright Earth like lighting during their night time? Humans do not have night lights around their homes and cities which are 2500 (50AU ^2) brighter than our daylight. Our rods and cones will just saturate and perhaps even get damaged under such intense illumination.
Further, from our line of sight (Earth) the KBO will ALWAYS have day time. Since the side facing us is to a good approximation, the side facing the Sun. Unless they want to artificially brighten their day side, we will not be seeing anything.
Therefore to summarize my arguments against such a search are –
Plausibility of evolution of intelligent life on a KBO.
The need for such bright light for an ET on KBO.
We are always seeing the day side of a KBO from Earth.
Hence, I think such a search should not be conducted. Some of these points are mentioned in the conclusion of the paper, and it is correct that we cannot predict the nature of another civilization or its biology. However, the basic laws of Physics and Chemistry are universal.
When people consider intelligent life, they often picture humanity. Most would not contend the fact that humanity is the only intelligent species on Earth. However, have we exhausted the search for traces of ancient, intelligent species? That is to say, have we considered the possibility an intelligent species existed millions of years ago, on or near Earth, with comparable intelligence? Jason Wright notes the dearth of literature on “indigenous technological species” in his recent paper. He contemplates that a search for Solar System artifacts can serve as a vector to answer the perennial question of whether life exists elsewhere.
Wright begins by providing a history of the search for extraterrestrial intelligence (SETI). Conventional SETI prioritizes interstellar radio signals, waste heat, or other methods to find life in the form of extraterrestrial intelligence. Within our local neighborhood, the search is biologically driven, focusing on the search for microorganisms on moons or biochemical markers as proxies for life. Wright makes the case to search for artifacts within our Solar System. While the exact probabilities are unknown, Wright postulates it should be easier for the origin of any artifacts or technosignatures to “be local, [rather than] an extraterrestrial species crossed interstellar space and deposited [it] here”. Given this, he coins the phrase “prior indigenous technological species” to convey an ancient species dwelling in the Solar System. Such a species possessed high intelligence but has since become either extinct or left the Solar System.
Any artifacts from this species could remain here to inform us of their past and Wright argues there are various locations to search for these artifacts, even on Earth. Many may argue the post-Cambrian fossil record should remove all doubts of another intelligent species, particularly due to the existence of endocasts. However, it is impossible to unambiguously gauge intelligence and cognitive ability from the fossil record. Wright also mentions the “Earth is quite efficient, on cosmic timescales, at destroying evidence of technology on its surface”. Geologists do believe there is a technosphere which might leave impact on the fossil record. However, artifacts on billion year timescales would probably be destroyed by tectonic processes and, at best, one could probably detect unnatural isotopic ratios. There is also the question of magmatism on an early Earth-like planet. While the oldest crust is 4.4 billion years old, the early Earth suffered from magmatism. The modern continental crust, along with plate tectonics, would have emerged much later, potentially eradicating any traces of earlier intelligent life. Wright appears to favor searching in places with little surface restructuring (unlike Venus), such as Mars, and suggests the subsurface should be searched. Other areas of interest are old objects such as asteroids or Kuiper belt objects. Exactly what type of life would persist to leave artifacts is not mentioned and this warrants consideration given the climatic changes on Earth (and Mars/Venus).
Wright’s hypothesis could read as a script for a video game like Halo. The fact that his hypothesis can reflect science fiction (or a video game) does little to bolster a search. Furthermore, this paper is easily distorted, perhaps unfairly and to Wright’s distress, to make a claim that aliens existed in the past (see here, here, or here, for less low-brow articles see here or here). This concept of an indigenous technological species is as plausible as dragons or unicorns. There is no evidence against either mythical creature, but this has not fueled a search for them. To this blogger, it is not apparent how one searches for an artifact or technosignature. We assume it is something readily disentangled from nature, but we are limited by our anthropocentric machinations. It is unsettling to form argument where (i) the answer may be beyond recognition or (ii) a conclusion is that all evidence was simply destroyed. Furthermore, it appears that a non-detection can be rendered insignificant as one could always imagine a different condition for artifact preservation. If one’s hypothesis is not testable, then it does not merit scientific consideration.
In Loeb & Turner (2012), a new Solar System SETI method is described. If Kuiper Belt objects (KBOs) are artificially illuminated, we should be able to detect that based on how their brightness changes with distance (both from us and the sun).
If a KBO has artificial illumination on its surface, then its brightness should only decrease with distance (from us on Earth) squared (a geometric effect of the intensity of the light diluting as it gets further from the source, see Wikipedia’s explanation). But, if a KBO is illuminated solely by the Sun (as we expect them to be), the light is coming from the Sun, so the light gets diluted twice and we would expect it to decrease with distance to the fourth power. The distance from the Sun to the KBO and from the Earth to the KBO are essentially the same because the Earth is relatively close to the Sun. KBOs are 30-50 AU away from the Sun while Earth orbits snuggly at 1 AU. So the distances can only be different by at most at most ~3%, a subtlety I feel should have been made explicit in the paper. Presumably this power law identification could be performed (at least in a rudimentary sense) by putting the data into log space and identifying the linear trend of brightness as a function of distance (hopefully with a slope of -2).
Another interesting tidbit was the use of a unit defined as 1% of the solar daylight illumination of Earth, ~ 1.4 · 10^4 erg/(s cm^2). They state that this corresponds roughly to the illumination in a brightly lit office or to that provided by the Sun just as it rises or sets in a clear sky on Earth. I spent an inordinate amount of time wrestling with this fact, as it is repeatedly used as a baseline in the paper and is not immediately obvious to me what this statement even means. It doesn’t feel like outside my office is 100x brighter on a sunny day, but who knows.
This paper discusses the possibility of detecting artificial illuminated objects in the outskirt of solar system by measuring the flux variation with respect to distance.
The authors begin by arguing that there are two basic illumination classes we use, one is thermal (light bulb) and the other one is quantum (LED). The spectra of those light sources should be very different from natural sources. Therefore, it is possible to detect those sources.
Further, the authors discuss whether we could detect those sources with our current technology and their conclusion is that we could be able to detect illumination level on the equivalent scale of large cities on Earth out to the outskirt of Solar system.
Additionally, the authors quantitatively calculate the flux versus distance slope difference between artificial objects (-2) and natural sources (-4). There are other factors that could affect this slope, including changing phase angle. Those factors influence the flux variation on the scale of 0.1 magnitude and should be able to be averaged out by long period of observation.
Finally, the authors argue that the chances of detecting such objects will be higher when the “dark side of the planet is more in view” or the host star of planet has went into a white dwarf so that the light contrast will be higher.
