Enceladus, Revisited

Tomorrow is a very important day.

Around 1400 UTC tomorrow (0700 PDT) NASAs Cassini spacecraft will do a flyby of the south pole of Enceladus, at an altitude of 99 km (62 miles). This is the first close flyby of Enceladus since early March 2011.

At that time we learned that the Tiger Stripes on the south pole of Enceladus were being heated by an energy source of some 15.8 gigawatts. 1.4 gigawatts is the absolute maximum Enceladus should be able to generate, for a matter of a few short seconds, if all of her potential geothermal and radioactive energy were concentrated into the same place at the same time. Tomorrow we will learn if the Tiger Stripes have cooled, or if they are maintaining this heat output at a consistent (or increasing) rate. All evidence so far indicates that the heat signature is not decreasing.

Tomorrow we'll know for sure. And things may become a lot more interesting.

You can track the Cassini/Solstice mission tomorrow here:
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20111001/

Tiger, tiger, burning bright

Typically, in astronomy, "The Great Silence" refers to the (not actually surprising) lack of intelligent radio transmissions emanating from the nearby stars.

Today it apparently refers to the lack of intelligent or otherwise radio transmissions emanating from the commercial media regarding the NASA announcement of a high energy heat source on Saturn's moon Enceladus.

By "commercial media" I mean CNN, BBC, Fox and even Weekly World News. I gave up the search after WWN, although I was pleased to learn there that space aliens have been ditching the bodies of human abductees onto the surface of the moon, minus their bones. How DO they keep scooping larger news agencies like the BBC?

Anyway, none of the news outlets I checked had picked up the NASA story (the real one). Given the incredible opportunity this story presents for each of the media outlets to royally eff it up in their own special way, I was inclined to give NASA credit for cleverly hiding the story in plain sight and wording it so blandly that the media didn't notice it. But that would imply that the NASA press corp was "clever", and so far the available data does not fit that hypothesis very well.

My next hypothesis was that the news outlets did read the story and understand its implications, but were taking the responsible path of allowing the information to trickle into the public's consciousness in its own time. Then I remembered that I had included Fox News in my list.

The only conclusion I was left with was that the science editors of the various media really genuinely didn't understand the importance or the implications of the press release. So, allow me to break it down into itty bitty words for the journalists.

Saturn has a tiny moon called Enceladus. "Tiny" as in about 500 kilometers, or about 300 miles, in diameter. For comparison, if Enceladus happened to be sitting on Ellensburg WA, the sphere of the moon would reach to Aberdeen WA to the west, Pullman WA to the east, Warm Springs OR to the south and nearly to Chilliwack BC to the north. So, "tiny" as far as moons go, but you wouldn't want to have to store it in your basement.

Enceladus has an ice mantle which is about 5km thick, which is much thinner than the ice mantles of the Jovian moons. Beneath that is a salt water ocean, which happens to be rich in simple organic chemicals.

Now, here's the rub. Enceladus should be frozen solid. There really isn't a logical reason why the interior of Enceladus is warm enough to melt the ice. There are two standard candidates for this, the first being tidal expansion and contraction from the gravitational relationship with Saturn and Dione (another of Saturn's moons), and the second being radioactive decay of superheavy metals within the rocky interior of Enceladus. Neither of these explanations hold much water.

Mimas, yet another of Saturn's moons, is closer still to Saturn but frozen stone cold solid. And you wouldn't really expect a world with a gravity 0.01 times that of earth to have made very much uranium.

Furthermore, Enceladus' heat does not seem to be evenly distributed around the globe, but concentrated in one single very small area. A tidally induced underwater volcano might account for this, but we would expect that to be situated near the equator, either facing or opposing Saturn (like our own moon, Enceladus is tidally locked with Saturn, with the same side always facing the planet). However, it turns out that our lone hot-spot is precisely at the south pole.

Still, knowing that there was in fact a hot-spot, scientists computed the absolute maximum heat output which could be generated by a combination of tidal dynamics and radioactive decay. The very generous number they arrived at was 1.4 gigawatts.

The hot-spot is called the "tiger stripes", because it is a region of four nearly parallel and evenly spaced trenches, each about 80 miles long by 1 mile wide. Cassini recently measured the heat from the tiger stripes as 15.8 gigawatts. More than ten times the maximum which could be generated by any known natural phenomenon.

So, what are we looking at here?

The official SWAG (stupid wild-assed guess) from NASA and JPL is that it is a somehow anomalous flareup that Cassini just happened to capture. The problem with this is that the original 1.4 gigawatt number was the anomalous flareup. So we can probably throw that one out. That leaves us with two possibilities. Either we're seeing a previously unknown natural phenomenon, or we're seeing a previously unknown artificial phenomenon. Either way we're going to need a lot more data and a lot more research. And suddenly Saturn's moon system looks a lot more interesting.

Cassini finds 15.8 gigawatt energy source on Enceladus

Here is the link from the NASA story. Will post much more later, class starting in a couple of minutes.

The commercial media doesn't seem to have picked this up yet. When they do, they will make a mess out of it. Here's the full NASA press release, minus graphics:

================================================================

Cassini Finds Enceladus is a Powerhouse
03.07.11

PASADENA, Calif. – Heat output from the south polar region of Saturn's moon Enceladus is much greater than was previously thought possible, according to a new analysis of data collected by NASA's Cassini spacecraft. The study was published in the Journal of Geophysical Research on March 4.

Data from Cassini's composite infrared spectrometer of Enceladus' south polar terrain, which is marked by linear fissures, indicate that the internal heat-generated power is about 15.8 gigawatts, approximately 2.6 times the power output of all the hot springs in the Yellowstone region, or comparable to 20 coal-fueled power stations. This is more than an order of magnitude higher than scientists had predicted, according to Carly Howett, the lead author of study, who is a postdoctoral researcher at Southwest Research Institute in Boulder, Colo., and a composite infrared spectrometer science team member.

"The mechanism capable of producing the much higher observed internal power remains a mystery and challenges the currently proposed models of long-term heat production," said Howett.

It has been known since 2005 that Enceladus' south polar terrain is geologically active and the activity is centered on four roughly parallel linear trenches, 130 kilometers (80 miles) long and about 2 kilometers (1 mile) wide, informally known as the "tiger stripes." Cassini also found that these fissures eject great plumes of ice particles and water vapor continually into space. These trenches have elevated temperatures due to heat leaking out of Enceladus' interior.

A 2007 study predicted the internal heat of Enceladus, if principally generated by tidal forces arising from the orbital resonance between Enceladus and another moon, Dione, could be no greater than 1.1 gigawatts averaged over the long term. Heating from natural radioactivity inside Enceladus would add another 0.3 gigawatts.

The latest analysis, which also involved the composite infrared spectrometer team members John Spencer at Southwest Research Institute, and John Pearl and Marcia Segura at NASA's Goddard Space Flight Center in Greenbelt, Md., uses observations taken in 2008, which cover the entire south polar terrain. They constrained Enceladus' surface temperatures to determine the region's surprisingly high output.

A possible explanation of the high heat flow observed is that Enceladus' orbital relationship to Saturn and Dione changes with time, allowing periods of more intensive tidal heating, separated by more quiescent periods. This means Cassini might be lucky enough to be seeing Enceladus when it's unusually active.

The new, higher heat flow determination makes it even more likely that liquid water exists below Enceladus' surface, Howett noted.

Recently, scientists studying ice particles ejected from the plumes discovered that some of the particles are salt-rich, and are probably frozen droplets from a saltwater ocean in contact with Enceladus' mineral-rich rocky core. The presence of a subsurface ocean, or perhaps a south polar sea between the moon's outer ice shell and its rocky interior would increase the efficiency of the tidal heating by allowing greater tidal distortions of the ice shell.

"The possibility of liquid water, a tidal energy source and the observation of organic (carbon-rich) chemicals in the plume of Enceladus make the satellite a site of strong astrobiological interest," Howett said.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The CIRS team is based at NASA's Goddard Space Flight Center in Greenbelt, Md., where the instrument was built.

On Intelligence, part three

Signs of Life

Electromagnetic radiation is of limited utility for interstellar communication, precisely because it is limited to the speed of light. It is not terribly difficult to imagine a scenario in which a civilization on a star was in EM communication with a colony of its own on another star one parsec away. Of necessity, this would be in the form of reciprocal one-way communications, perhaps the interstellar equivalent of three-year-old newsreels. But it seems unlikely that this sort of communication would be uninterrupted and continuous.

Over distances much larger than a parsec, any semblance of two-way communications
breaks down to the point of utter futility. The only place in our galaxy where EM has any conceivable utility for two-way communications over interstellar distances is near the galactic center, where “interstellar distances” are in fact quite short. However, with as much radiotelescope time as has been devoted to this region of the sky generally, we have not yet detected artificial signals there. For the rest of the galaxy, any species attempting two way communication across interstellar space using EM may, almost by definition, not be considered “intelligent”.

Unfortunately, we are still limited to searching in this spectrum, even with the
understanding that no species in their right mind would be broadcasting on it, at least in terms of two-way interstellar communication. So we must look for reasonable purposes for transmitting high-output, uniformly pulsed signals which are not intended to be responded to. As we have only earth-bound human culture as an analogue from which to anticipate alien technologies, we must look at human civilization and technologies which have, by design and intent, broadcast proportionally large-output transmissions which were deliberately and readily identifiable as artificial.

Perhaps the best candidates which come to mind are “aids to navigation” such as buoys and lighthouses. On earth, these tend to be self-powered, self-repairing, and capable of broadcasting light, sound and/or radio signals easily discernible from the background, in an easily recognizable and repeating pattern. An analogous structure in deep space might well remain “on station”, transmitting for eons after the civilization which constructed it had become extinct. Antiquity would be no great barrier to utility, as the age of the phased light or radio transmissions would be of little relevance for determining the object’s relative location. A “buoy” placed on-station ten thousand years ago by a species long extinct would still have utility for space-faring civilizations today, and would provide earthbound SETI researchers with proof of extra-terrestrial intelligence.

Buoys, by definition, are undeniably artifacts; they must be designed in such a way as to not be possibly mistaken for a naturally occurring phenomenon. They tend not, however, to be scintillating conversationalists. If in fact such artifacts do exist throughout the galaxy, and are in fact transmitting on frequencies which humans are capable of receiving, the first “intelligent” communication we receive from an alien civilization may be something like “dit dah dah dit”, repeated over, and over, and over, and over…tantalizing, as it would tell us absolutely nothing about the species which created it other than the fact that they had need of navigation aids at some point in their history. However, given their potential longevity, message redundancy, signal strength and likely ubiquity (if in fact other species in the galaxy are spacefaring, by whatever means), deep-space aids to navigation, if
such exist, seem very likely candidates for our first unmistakable and undeniable contact with an extraterrestrial intelligence.

The argument against navigational buoys being our first contact is that we haven’t heard any yet. There are four possible reasons for this. 1) they are too far away, or for whatever other reason the signal-to-noise-ratio is too low for us to detect with our existing telescopes, 2) they are not transmitting in the spectra we are looking, or even in a spectrum that we are aware of, 3) we are receiving transmissions from them already and have simply not recognized then as such, or 4) they don’t exist.

SETI today

Presently, SETI predominantly uses very large earth-based radiotelescopes such as
Arecibo Radio Observatory in Puerto Rico to “look” at the sky at that latitude as the earth rotates under it. Because this is a “fixed” antenna located on a rotating body, SETI first looks for signals which increase and then decrease at a rate consistent with planetary rotation and the passive field-lobe of the array; this signal-strength bell-curve is called a “Gaussian”. Any EM source which is not originating on earth will exhibit this, whether it is a star, an earth-orbiting satellite or an Aldebaranian disc-jockey. Strong narrowband EM pulses of smaller pulse-length than the duration of the Gaussian are also looked at, and “triplets” (evenly spaced short pulse-length EM pulses which conform in signal strength to a Gaussian) are especially interesting.

Once a signal of interest has been detected, verified by multiple computers and isolated from terrestrial (or near-extraterrestrial, such as satellite) radio frequency interference, it is then examined for persistency. A “persistent” signal is one which is observed on more than one occasion with the same frequency and same location, by one or more radiotelescopes. One current data set of 80,704 Gaussians contained 2,868 candidates which matched once (2 occurrences), 111 candidates which matched twice (3 occurrences), and 4 candidates which matched three times (4 occurrences). Within this particular data set there were no candidates which matched more than three times. As this particular search construed “persistency” as being within 2.5 arc minutes and 50 Hz frequency, the persistent signals in this sample must be presumed to be only randomly and incidentally so.

Much of the search to date has focused on the 1000 to 10,000 MHz “waterhole”, with the presumption that anyone willfully transmitting EM over interstellar distances would do so in frequencies least impeded by background noise. Again, the likelihood of any species technologically intelligent enough to do so actually attempting two-way communication across interstellar distances with EM is, one hopes, rather small; aids to navigation or similar beacons, however, would by necessity utilize the water hole if they were transmitting EM at all. All other things being equal, then, as EM is the only means we have of searching for extraterrestrial intelligence at this point in our history, if we are serious about locating proof of extraterrestrial intelligence we need to consider the virtue of searching for radio- or light-transmitting artifacts rather than actual coherent communication, and optimize our search toward finding those things which are most likely to be transmitting on the frequencies we’re searching.

The disadvantage of searching for buoys, obviously, is that once the initial excitement of discovery wears off, they really aren’t very interesting. The advantage is that what buoys lack in eloquence they make up for in tenacity, so there’s no worry about “missing the signal”. Any systematic search of the sky on the right frequency and sensitivity will find it eventually, and once it is located it is easy to verify independently with other antennas, and could be easily monitored continuously as the earth rotates by a series of antennae at different longitudes around the globe. For a search such as this, then, one large array is
infinitely preferable to a large number of smaller arrays.

However, for detecting more “interesting” and potentially more ephemeral signals, a
much larger number of smaller antennae would seem to be optimal. A 3-meter dish
antenna is the minimum needed to “see” in the water hole. Already, SETI-inclined
amateur radio enthusiasts have been building very small radio telescopes from old
satellite television antennas; the SETI League has established Project Argus to integrate the searches of these amateur radio-astronomers via e-mail and newsletters.

Concurrent with but independent from this “SETI at home” amateur radio astronomy is
“SETI@home”, which utilizes millions of personal computers around the world to
analyze SETI data obtained from Arecibo or other giant radio arrays. Essentially
SETI@home is using unused processing time on individual personal computers as a giant supercomputer. The individual user is given a screensaver-like program which processes units of parsed-out data from Arecibo. Because SETI@home has over 2,000,000 participants, extraordinary amounts of data are able to be processed in a very small amount of time.

“Combining the forces” of the SETI League and SETI@home, it would be possible to
create an array of perhaps millions of small antennae scattered around the world,
interfaced via personal computers. If an individual antenna picked up an interesting
candidate, the personal computer it was attached to could perform a preliminary data
analysis, and then automatically prompt all of the antennae in its hemisphere to train on the same Right Ascension and Declination. All data collected would then be transmitted to a central supercomputer for further analysis. In this way, a truly global antenna array (if only 1% of current SETI@home participants participated in this, that would commit 20,000 new antennae to the search) could be built for well under $500 per participant, and almost no hardware or software overhead whatsoever for the university organizing it.

The existing single massive antenna approach, used in tandem with the sort of
Shoestring Budget Global Array (SBGA) proposed here, could significantly accelerate
our search for extraterrestrial intelligence.

And, really, what could be cooler than turning your old satellite dish into a personal radiotelescope to hunt for aliens with?

On Intelligence, part two

Inter-species communication on earth has met, to date, with only limited success. The most successful instances of inter-species communication have all involved a wide spectrum of visual, auditory, tactile and other sensory cues, such as the Fouts' work with chimpanzees. Crafting a communication which can be broadcast on radio frequencies and which will be comprehensible to an intelligence other than ourselves is not a small task. Any communication which is deliberately transmitted to other stars should, at the very least, be readily comprehensible to all humans from all cultures on this planet, and it should also be readily comprehensible to all other species on this planet which are estimated to have intelligence in any way analogous to humans. More, it should be such that all such species comprehending it would be able to convey their comprehension of it to the humans transmitting it in such a way that the humans would understand conclusively that
comprehension was being conveyed. This problem of “comprehensibly conveyed
comprehension” is crucial to SETI.

For example, if we were to attempt to convey our intelligence to a spiny anteater (which has a much higher neocortex-to-body-weight ratio than humans, and is therefore, by some definitions of intelligence, significantly and demonstrably more intelligent than we are) by means of tapping out “x, xx, xxx, xxxxx, xxxxxxx”, then a response from the anteater which indicated its comprehension that it was being communicated with might be tapping out “x, xx, xxx, xxxxx, xxxxxxx”, whereas a response which indicated its comprehension of the meaning of the communication might be tapping out “xxxxxxxxxxx, xxxxxxxxxxxxx, xxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxxxxxx”, in this case simply continuing the string of prime numbers for the same consecutive interval as the transmission. However, responses such as 15 taps or 120 taps (the units of the original message added or multiplied together, respectively) might also convey comprehension of part of the meaning of the message, if not the actual intent. However, it is not impossible that the spiny anteater, with its relatively massive neocortex, is possessed of a mathematics so far advanced of our own that the “obvious” relationship of these numbers to it would be utterly incomprehensible to us or even unrecognizable as an intelligent response.

To date, our attempts at deliberate communication with extraterrestrials have been mostly undecipherable even to the majority of humans living in the same culture as the scientists creating the messages. Obviously, this cannot work; language is by definition symbolic, and without a universal (even if rudimentary) symbol set, communication will not occur.

We may presume, for example, that hydrogen occurs in any place that life exists.
However, humans have only been aware of the existence of hydrogen since Paracelsus, and it was not until Cavendish that it was isolated as a unique gas, and it is very unlikely that Neils Bohr would have recognized the Schrodinger/Heisenburg model of a hydrogen atom as anything related to chemistry. So it is probably unreasonable to assume that a non-human intelligence would have any ability to decipher a human’s symbolic representation of a hydrogen atom, from any given point in human history.
Dolphins and other cetaceans, for example, are believed by many humans to be likely terrestrial candidates for non-human intelligence. It is unlikely, however, that most dolphins would understand a human’s symbolic representation of a hydrogen atom, or binary notation of numerals, or consecutive strings of prime numbers. At least, as of this writing, no dolphin has clicked a consecutive string of prime numbers to any human capable of comprehending the significance of prime numbers; it may simply be that dolphins consider humans mathematically inept.

Symbolic representations of hydrogen atoms, binary notation, and prime numbers
each, at one time or another, have been deliberately transmitted into space, in hopes that some other species somewhere might recognize us as intelligent. Perhaps the most eloquent, although probably equally incomprehensible, messages sent
deliberately into deep space to date were not a radio or light transmission at all, but rather two identical drawings etched in 6” by 9” gold-anodized aluminum plates, attached to the Pioneer 10 and 11 spacecraft.

Punch magazine was quick to point out some possible misinterpretations of the etchings. Among the quotes of the hypothetical alien scientists attempting to decipher the etchings--

“A suggestion that it could be a map of some metropolitan railway has been made to us, but we feel that this fails to take into account the arrowed position of a capsized yacht…”

“The illustrated talent for the creature on the right to be capable of firing arrows from the shoulder is a particularly sinister turn…”

Indeed.

On Intelligence, part one

The following is part of an essay I wrote back in 2000 or something, as part of a 600-level course in astronomy and exobiology. I'm not big on recycling old material, but I'm even less big on re-inventing the wheel, and there's material here I want to present before delving deeper into the topic of extra-terrestrial intelligence. I've edited it here to read a bit less like a post-grad paper, but I'm leaving the original content more or less intact. I'm going to present this here in installments, because the original essay is rather long. I probably won't disclaimer all of the later installments, or excerpts from other essays from that time, so let this disclaimer stand for all of them.

=========================================

The first obstacle in the path of finding extraterrestrial intelligence is to define
“intelligence”. Even when discussing terrestrial animals, the concept of “intelligence” is at best an abstraction. Some criteria for intelligence have been such things as total brain mass, brain-to-body-weight ratio, neocortex-to-bodyweight ratio, communications and behavior. Using these criteria, reasonable arguments may be made for the intellectual superiority of such creatures as humans and other apes, crows, cetaceans, mice, dogs, cats, bees and spiny anteaters. It is questionable whether humans possess the intellectual capacity to recognize intelligence in other species, or to meaningfully define intelligence
generally. From a purely evolutionary standpoint, every species which currently exists would be, by definition, equally “intelligent” for its evolutionary niche or it would have been out-competed by a more “intelligent” species.

However, for the purposes of the current search for extraterrestrial life, we can eliminate a great many of the abstract considerations of what constitutes actual intelligence, and simply focus on the specific types of intelligence which might produce EM transmissions. As EM energy is the first (and currently only) possible means for humans to communicate beyond this planet and beyond the solar system, we are limited to this spectrum, and any species communicating by other than EM means are self-eliminated from the search. Within the EM spectrum, we can narrow our definition of “intelligence” to mean the type of intelligence which can produce narrowband EM transmissions which are pulsed into a pattern which is readily identifiable as non-random. This effectively limits the search for extraterrestrial intelligence to such intelligences as humans, which are now able to produce such EM transmissions artificially, and fireflies, which are capable of producing such transmissions biologically. There is no reason to postulate the greater
likelihood of biological or artificial ability to transmit in the EM spectrum, nor is there any reason to assume that either would necessarily be more likely to possess a type of intelligence similar to our own. However, it is
possible that a species which developed artificial means of transmitting and receiving EM energy would have undergone a greater number of analogous steps in their intellectual evolution to our own, than a species which had evolved a biological means of transmitting and receiving in this spectrum. For this reason, we will focus our search on those species which have developed EM technology independent of any biological mechanism for producing this, whether or not we would be able to discern the difference from Earth-based telescopes.

We have not yet discovered another world within our own solar system which
conclusively harbors life, although Europa is a prime candidate. As we have observed no evolutionary models other than our own, we can, at this point, only extrapolate from our own evolution what course the evolution of intelligence might take on another world. The steps in our own evolution which might reasonably be expected to have extraterrestrial analogues leading to the development of EM technology are as follows:

Impeti 1: Organic chemicals to prokaryotic life
Evolutionary Impeti 2: Prokaryotic life to eukaryotic life
Evolutionary Impeti 3: Cambrian explosion (2011 note: I was unaware of the Ediacaran Biota when I wrote this, which fundamentally changes this part of the equation)
Evolutionary Impeti 4: Prehensility
Evolutionary Impeti 5: Technology
Evolutionary Impeti 6: Intelligence (development of EM technology)

By this definition, homo sapiens became an intelligent species in September of 1895 ev, when Guglielmo Marconi became the first intelligent mammal on earth. Now, a little more than a century since this achievement, humans are able to demonstrate their intelligence every time they place a call on a cellular telephone.
Prehensility is of course critical, as species which might otherwise be construed as
“intelligent” which have no physical means of creating technology (such as some
cetaceans) tend not to build artifacts capable of transmitting in the EM spectrum. It is over-simplifying the situation, however, to assume that an orderly progression from the digging-stick to the cellular telephone (or radio telescope) is inevitable for any prehensile and technologically inclined species.
Even species which happen to develop EM technology may not utilize it for
communications, either because they have methods of communication which are superior
to EM, or simply because it does not occur to them to do so. For example, many human
cultures have, independently of one another, developed both cups and strings; however the number of human cultures who have adapted these technologies to create crude telephones out of them is significantly small. The analogy is not a bad one; SETI itself is rather like standing on an island with a cup-and-string telephone and sticking one cup to our ear and holding the other cup out to the sea, and hoping to hear people talking on some other island. And then shouting into one cup while holding the other cup out to the sea, hoping someone out there will hear us.

More on object 1991VG

Here is the web page for the JPL small-body database for 1991VG, which is a possible Bracewell Probe candidate. My original post on this, titled The Sentinel, seems to be getting a lot of airplay, so I will be researching it further.

July of 2017 is our next launch window for either a crewed or robotic mission to 1991VG. Hopefully we'll have heavy lift capabilities available at that time.

The Sentinel

In 1950 physicist Enrico Fermi, while considering the presumed ubiquity of technological civilizations around the Milky Way, over lunch one day asked the simple question, "Where are they?". By which he meant, even if advanced alien civilizations were exceedingly rare, if they existed at all some of them, even traveling at speeds of 5% of the speed of light (which may in fact prove to be about the maximum speed possible for space travel, which will be the subject of another post in the near future) or even slower, should eventually have colonized or at least visited all of the galaxy and already contacted us, either in person or by means of a probe of some sort. Meaning, the question of whether or not there are other technological civilizations in the Milky Way should be nonsensical; either there are none, or they're already here and downtown Seattle should look like Mos Eisley Spaceport. I mean, even more than it already does.

 The fact that earth is not already crawling with aliens (no disrespect intended to the Aldebaranian's mode of locomotion, its just an expression), combined with the lack of an unambiguous signal received by any of the SETI telescopes, is sometimes referred to as the Great Silence, or the Fermi Paradox.

I think this is from the brilliant comic XKCD, if you know otherwise please let me know!

There are a couple of possible explanations for this. The first is that there simply aren't any other technologically advanced civilizations in the Milky Way. As a generation which has grown up on a daily diet of science fiction, this seems ironically uncomfortable. But it may well be the case. Of the billions of species which have ever lived on earth we are the only one which has proven capable of space travel or radio broadcasts. Or any other technology more sophisticated than a digging stick or a broken rock. Life, even intelligent life, may well be ubiquitous, but technologically advanced civilizations may be vanishingly rare.

Another possibility is that interstellar space travel, either for reasons we do understand or for reasons we do not, may simply not be feasible. This is also uncomfortable for us, but it may be true. It is almost certainly true that crewed space travel will never exceed about 10% of the speed of light, for a variety of reasons (not the least of which being that by 12% of the speed of light, a grain of sand hitting the vessel would react with the force of a hydrogen bomb). But at 10% (or even 5%, which we have the technology to achieve right now) of the speed of light we could get to the nearest stars within a human lifetime. But there may be barriers to traveling through interstellar space which we haven't even considered.

Another possibility, one championed by UFO enthusiasts, is that our skies and streets ARE crawling with aliens, we just need to pull our heads out of our recta and realize it. This isn't quite as far-fetched as it sounds; some have posited that the natives in Hispaniola could not see Columbus's ships until their shamans or whatever they're called there did. This may be apocryphal, but it is true and demonstrable that the human mind filters out data it isn't prepared to process. If this sounds like BS to you, take this simple test here, and then come back to this post. My personal feeling is that this possibility is pretty unlikely, but I wanted to include it specifically because so many discussions of the Fermi Paradox willfully exclude it, which is simply bad science. 

Yet another possibility is that alien civilizations have visited here in the past, and then (tinkered with chimpanzi genes to invent us/used their antigravity technology to move around a bunch of rocks/put on funny hats and modeled for neolithic artists/figured we were beyond hope and left never to return/fill in the blank). This is also possible; there is an entire field of research called SETA, or the Search for Extraterrestrial Artifacts. SETA to date has not proven any more fruitful than SETI, with one possible exception which I'll talk about in a moment. In order for an artifact to be unambiguously "alien" it needs to be something truly beyond the abilities of human artificers to construct. For example, the pyramids at Cheops are amazing, but well within the capability of bronze-age builders if you happen to have many of them. If the pyramids had been made out of titanium, for example, THAT would be a pretty good indication that it was not built by bronze-age humans.

One type of artifact especially interesting to SETA researchers is something called a Bracewell Probe, first proposed by Ronald Bracewell in 1960. It is an autonomous robot probe used essentially as a message in a bottle to another star, which has crammed into its memory banks all of the information from and about the originating species that it's creators deemed worthy to put in it. If the probe happens to have the ability to utilize resources in other star systems to self-replicate, it is called a von Neumann probe and then has the ability to cover a lot more interstellar territory. Arthur Clarke, in his novel and then movie 2001: A Space Odyssey, imagined that an advanced alien civilization might send out millions of such probes to monitor promising worlds around the galaxy. Rather than try to analyze the development of each of the billions of species the probes were monitoring, the aliens set up a simple test. They placed a Bracewell probe on the moon. Any species on earth which advanced to the point of landing on the moon would find the probe, and trigger it to give the previously earthbound species further instructions.  

If you watched 2001 but didn't quite understand what was happening in that scene, or in any part of the movie, that's okay. Clarke was brilliant, and director Stanley Kubrick was brilliant, but the combination of the two of them was just effing weird.

So, we've been to the moon, and haven't found a Bracewell probe there. But oddly enough, we may actually have found one even closer than the moon.

On 6 November 1991 astronomer Jim Scotti discovered what he thought was a small near-earth object (asteroid), which was prosaically named 1991vg. NEO expert Duncan Steel at the University of Adelaide, Australia, analyzed 1991vg and made a truly startling discovery.  Based on the orbit of 1991vg, which trails the earth in its own orbit but sometimes closes range with earth for brief periods and then resumes its "station" behind it, and based also on the fact that light reflected from it indicates that the object is of a faceted nature (more like a shoebox than a basketball), there are three possible explanations for it. The first is that it is a naturally occurring asteroid. The second is that it is a piece of human-made space debris, left over most likely from the early Apollo missions. The third is that it is a self-propelled artifact of non-human origin. Through careful analysis and process of elimination, the third possibility has emerged as by far the most likely candidate. Really.

It is important to understand that Duncan Steel is probably the world's foremost expert of NEOs. He has written dozens of papers on various aspects of NEO research, and Steel and Scotti together have discovered and catalogued more NEOs than maybe all of the other researchers in the field combined. When Duncan Steel says "that's definitely not an asteroid and probably not human-made space junk", it's worthy of further investigation.

Here is his paper on the subject, in its entirety: SETA and 1991vg    

More research, obviously, must be done to determine the true nature of 1991vg. But if you happen to look up in the sky some night and see a giant baby swatting at satellites, don't say I didn't warn you.

Is there anybody out there?

This post is the first in what will be an ongoing series concerning SETL, SETI, SETA, and the ultimate question of  "if technologically advanced alien civilizations are commonplace and traveling all over the galaxy, why the hell haven't they landed here yet?". It's actually a more reasonable question than it appears to be at first glance.

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In 1924 Mars and the earth were going to to be closer, for a few days, than they had been since 1804. The US Navy was asked to maintain a period of radio silence in order to listen for Martian broadcasts. The Navy managed to remain silent, but so, apparently, did Barsoom.

 In 1960 astronomer Frank Drake created Project Ozma, which was earth's first serious attempt to use radiotelescopes to listen for signals from intelligent species elsewhere in the galaxy. Ozma looked specifically at the stars Tau Ceti and Epsilon Eridani, both considered at the time to be likely candidates. They, too, failed to produce an artificially generated radio signal (but Drake did, in the process, manage to discover boring old pulsars).  Not especially daunted by not finding obvious signals after searching only two of billions of stars, Drake proceeded to expand his search of the heavens. In 1961 Drake chaired a meeting at the National Academy of Sciences National Radio Astronomy Observatory in Green Bank, West Virginia. Now known simply as the "Green Bank Meeting", this gathering of 12 astronomers, physicists, biologists and others established the first serious scientific protocols for the Search for Extra-Terrestrial Intelligence, or SETI.

In preparing for the Green Bank Meeting, Drake created the now famous equation which bears his name:



In which

N = the number of civilizations in our galaxy with which communication might be possible

R^* = the average rate of star formation per year in our galaxy

f_p = the fraction of those stars that have planets

n_e = the average number of planets that can potentially support life per star that has planets

f_ℓ = the fraction of the above that actually go on to develop life at some point

f_i = the fraction of the above that actually go on to develop intelligent life 

f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

 

Many variants and modifications of the Drake Equation have appeared since it was first published. It is probably best known from Carl Sagan and Star Trek. Some of the variables we now have pretty good estimates for. In each case the numbers are much higher than originally anticipated by Drake. The number of old, stable stars in the Milky Way is many times larger than was imagined in 1961. The number of these which have habitable worlds is also much higher than previously imagined. How ubiquitous life is on habitable worlds remains to be seen; if life is found on Europa and Enceladus, and fossils are found on Mars, then  f_ℓ will be assumed to be a very large number.

f_i, f<sub>c and L remain unknowns, but are tempered by the fact that to date we have no solid evidence of alien technology, either as radio signals, artifacts or direct contact and observation. 

It is important to understand that SETI itself is a gross misnomer. It is not possible to search for intelligence. It is possible to search for life on other worlds, and it is possible to search for technology on other worlds, but intelligence itself is almost impossible to identify, even here on earth. We observe behaviors in cetaceans, cephalopods, corvids, canines, felines, pachyderms and even some primates which we interpret as intelligence. On the other hand, we occasionally observe behavior in simple eukaryotes, prokaryotes, viruses and even sub-atomic particles which might be considered intelligent if we observed it in a vertebrate. Even among our own species, we have very little understanding of what "intelligence" means, and how or if that can be qualified or quantified in a meaningful way. But, to the very best of our knowledge, no species on earth other than ourselves has ever developed technology more sophisticated than a broken rock or a digging stick.  


Even very advanced human cultures did not invent the technology to transmit and receive radio waves until Marconi. And as human technology progresses, we are now broadcasting fewer and fewer radio signals into space simply by virtue of using more microwavelength communications and fewer medium and high frequency communications. Even if another civilization followed exactly our trajectory of technological development, there may be only a window of less than a century in which they are broadcasting distinct signals in the EM spectrum. We simply don't know.


Searching for extraterrestrial technology by listening in the radio spectrum, because it presupposes that the entities sending the signal have a transmitter which we can receive, is only a baby step above tying a string to two soup cans and holding one can to our ear and the other to the night sky. In other words, the sky may be teeming with technologically advanced civilizations and we'd never know it, because even though they're technologically advanced, we aren't. Whatever the reason (and we'll be exploring some of them in the coming weeks here), we have not yet found a conclusive radio signal from space aliens.

We have, however, found some not-quite-conclusive signals of interest. The most interesting was found by Jerry Ehman in 1977, and is known as the "WOW! signal" because of a hand-scrawled note on the digital printout. It was strong, narrowband, clearly not from our solar system, met all of the parameters SETI researchers have expected, lasted 72 seconds...and was never heard again.</sub> 

 

_{SETI, more properly SETT, continues. Radiotelescopes great and small comb the skies searching for a distinct and unambiguous signal from a technological race beyond our solar system. Whether we will find an unambiguous signal in our lifetimes, or ever, only time will tell.}

Underway

I'm going to be in the air or on the road for most of the next several days. This Android phone will be my only access to this blog until next Tuesday. Expect shorter posts without lots of photos and graphics, and probably more typos since I can't actually see all of the screen. If it works out, I'm going to start writing about SETI, and things like the Drake Equation, the Fermi Paradox and the Great Silence. The more we learn about abiogenesis and astronomy, the more ubiquitous life in the universe seems likely to be. But life, even intelligent life, does not equate to life which broadcasts radio signals. By this definition of "intelligence" there was no intelligent life on earth until Marconi, and Howard Stern and Rush Limbaugh are more intelligent than Isaac Newton. And fireflies, by communicating with deliberately phased electromagnetic pulses, were intelligent millions of years before Marconi.

Arguably there are many intelligent species on earth, from primates and cetaceans to corvids and octopi. But of the millions of species on earth past and present, only humans have developed tools more sophisticated than the digging-stick. One less species on earth, and earth would not be broadcasting its intelligence into the cosmos, in the form of Knight Rider reruns.