Contributor Post Created with Sketch. Saturday Night Science: Making Contact

 

“Making Contact” by Sarah ScolesThere are few questions in our scientific inquiry into the universe and our place within it more profound than “are we alone?” As we have learned more about our world and the larger universe in which it exists, this question has become ever more fascinating. We now know that our planet, once thought the centre of the universe, is but one of what may be hundreds of billions of planets in our own galaxy, which is one of hundreds of billions of galaxies in the observable universe. Not long ago, we knew only of the planets in our own solar system, and some astronomers believed planetary systems were rare, perhaps formed by freak encounters between two stars following their orbits around the galaxy. But now, thanks to exoplanet hunters and, especially, the Kepler spacecraft, we know that it’s “planets, planets, everywhere”—most stars have planets, and many stars have planets where conditions may be suitable for the origin of life.

If this be the case, then when we gaze upward at the myriad stars in the heavens, might there be other eyes (or whatever sense organs they use for the optical spectrum) looking back from planets of those stars toward our Sun, wondering if they are alone? Many are the children, and adults, who have asked themselves that question when standing under a pristine sky. For the ten year old Jill Tarter, it set her on a path toward a career which has been almost coterminous with humanity’s efforts to discover communications from extraterrestrial civilisations—an effort which continues today, benefitting from advances in technology unimagined when she undertook the quest.

World War II had seen tremendous advancements in radio communications, in particular the short wavelengths (“microwaves”) used by radar to detect enemy aircraft and submarines. After the war, this technology provided the foundation for the new field of radio astronomy, which expanded astronomers’ window on the universe from the traditional optical spectrum into wavelengths that revealed phenomena never before observed nor, indeed, imagined, and hinted at a universe which was much larger, complicated, and violent than previously envisioned.

In 1959, Philip Morrison and Guiseppe Cocconi published a paper in Nature in which they calculated that using only technologies and instruments already existing on the Earth, intelligent extraterrestrials could send radio messages across the distances to the nearby stars, and that these messages could be received, detected, and decoded by terrestrial observers. This was the origin of SETI—the Search for Extraterrestrial Intelligence. In 1960, Frank Drake used a radio telescope to search for signals from two nearby star systems; he heard nothing.

As they say, absence of evidence is not evidence of absence, and this is acutely the case in SETI. First of all, consider that you must first decide what kind of signal aliens might send. If it’s something which can’t be distinguished from natural sources, there’s little hope you’ll be able to tease it out of the cacophony which is the radio spectrum. So we must assume they’re sending something that doesn’t appear natural. But what is the variety of natural sources? There’s a dozen or so Ph.D. projects just answering that question, including some surprising discoveries of natural sources nobody imagined, such as pulsars, which were sufficiently strange that when first observed they were called “LGM” sources for “Little Green Men”. On what frequency are they sending (in other words, where do we have to turn our dial to receive them, for those geezers who remember radios with dials)? The most efficient signals will be those with a very narrow frequency range, and there are billions of possible frequencies the aliens might choose. We could be pointed in the right place, at the right time, and simply be tuned to the wrong station.

Then there’s that question of “the right time”. It would be absurdly costly to broadcast a beacon signal in all directions at all times: that would require energy comparable to that emitted by a star (which, if you think about it, does precisely that). So it’s likely that any civilisation with energy resources comparable to our own would transmit in a narrow beam to specific targets, switching among them over time. If we didn’t happen to be listening when they were sending, we’d never know they were calling.

If you put all of these constraints together, you come up with what’s called an “observational phase space”—a multidimensional space of frequency, intensity, duration of transmission, angular extent of transmission, bandwidth, and other parameters which determine whether you’ll detect the signal. And that assumes you’re listening at all, which depends upon people coming up with the money to fund the effort and pursue it over the years.

It’s beyond daunting. The space to be searched is so large, and our ability to search it so limited, that negative results, even after decades of observation, are equivalent to walking down to the seashore, sampling a glass of ocean water, and concluding that based on the absence of fish, the ocean contained no higher life forms. But suppose you find a fish? That would change everything.

Jill Tarter began her career in the mainstream of astronomy. Her Ph.D. research at the University of California, Berkeley was on brown dwarfs (bodies more massive than gas giant planets but too small to sustain the nuclear fusion reactions which cause stars to shine—a brown dwarf emits weakly in the infrared as it slowly radiates away the heat from the gravitational contraction which formed it). Her work was supported by a federal grant, which made her uncomfortable—what relevance did brown dwarfs have to those compelled to pay taxes to fund investigating them? During her Ph.D. work, she was asked by a professor in the department to help with an aged computer she’d used in an earlier project. To acquaint her with the project, the professor asked her to read the Project Cyclops report. It was a conversion experience.

Project Cyclops was a NASA study conducted in 1971 on how to perform a definitive search for radio communications from intelligent extraterrestrials. Its report [18.2 Mb PDF], issued in 1972, remains the “bible” for radio SETI, although advances in technology, particularly in computing, have rendered some of its recommendations obsolete. The product of a NASA which was still conducting missions to the Moon, it was grandiose in scale, envisioning a large array of radio telescope dishes able to search for signals from stars up to 1000 light years in distance (note that this is still a tiny fraction of the stars in the galaxy, which is around 150,000 light years in diameter). The estimated budget for the project was between 6 and 10 billion dollars (multiply those numbers by around six to get present-day funny money) spent over a period of ten to fifteen years. The report cautioned that there was no guarantee of success during that period, and that the project should be viewed as a long-term endeavour with ongoing funding to operate the system and continue the search.

The Cyclops report arrived at a time when NASA was downsizing and scaling back its ambitions: the final three planned lunar landing missions had been cancelled in 1970, and production of additional Saturn V launch vehicles had been terminated the previous year. The budget climate wasn’t hospitable to Apollo-scale projects of any description, especially those which wouldn’t support lots of civil service and contractor jobs in the districts and states of NASA’s patrons in congress. Unsurprisingly, Project Cyclops simply landed on the pile of ambitious NASA studies that went nowhere. But to some who read it, it was an inspiration. Tarter thought, “This is the first time in history when we don’t just have to believe or not believe. Instead of just asking the priests and philosophers, we can try to find an answer. This is an old and important question, and I have the opportunity to change how we try to answer it.” While some might consider searching the sky for “little green men” frivolous and/or absurd, to Tarter this, not the arcana of brown dwarfs, was something worthy of support, and of her time and intellectual effort, “something that could impact people’s lives profoundly in a short period of time.”

The project to which Tarter had been asked to contribute, Project SERENDIP (a painful acronym of Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) was extremely modest compared to Cyclops. It had no dedicated radio telescopes at all, nor even dedicated time on existing observatories. Instead, it would “piggyback” on observations made for other purposes, listening to the feed from the telescope with an instrument designed to detect the kind of narrow-band beacons envisioned by Cyclops. To cope with the problem of not knowing the frequency on which to listen, the receiver would monitor 100 channels simultaneously. Tarter’s job was programming the PDP 8/S computer to monitor the receiver’s output and search for candidate signals. (Project SERENDIP is still in operation today, employing hardware able to simultaneously monitor 128 million channels.)

From this humble start, Tarter’s career direction was set. All of her subsequent work was in SETI. It would be a roller-coaster ride all the way. In 1975, NASA had started a modest study to research (but not build) technologies for microwave SETI searches. In 1978, the program came into the sights of senator William Proxmire, who bestowed upon it his “Golden Fleece” award. The program initially survived his ridicule, but in 1982, the budget zeroed out the project. Carl Sagan personally intervened with Proxmire, and in 1983 the funding was reinstated, continuing work on a more capable spectral analyser which could be used with existing radio telescopes.

Buffeted by the start-stop support from NASA and encouraged by Hewlett-Packard executive Bernard Oliver, a supporter of SETI from its inception, Tarter decided that SETI needed its own institutional home, one dedicated to the mission and able to seek its own funding independent of the whims of congressmen and bureaucrats. In 1984, the SETI Institute was incorporated in California. Initially funded by Oliver, over the years major contributions have been made by technology moguls including William Hewlett, David Packard, Paul Allen, Gordon Moore, and Nathan Myhrvold. The SETI Institute receives no government funding whatsoever, although some researchers in its employ, mostly those working on astrobiology, exoplanets, and other topics not directly related to SETI, are supported by research grants from NASA and the National Science Foundation. Fund raising was a skill which did not come naturally to Tarter, but it was mission critical, and so she mastered the art. Today, the SETI Institute is considered one of the most savvy privately-funded research institutions, both in seeking large donations and in grass-roots fundraising.

By the early 1990s, it appeared the pendulum had swung once again, and NASA was back in the SETI game. In 1992, a program was funded to conduct a two-pronged effort: a targeted search of 800 nearby stars, and an all-sky survey looking for stronger beacons. Both would employ what were then state-of-the-art spectrum analysers able to monitor 15 million channels simultaneously. After just a year of observations, congress once again pulled the plug. The SETI Institute would have to go it alone.

Tarter launched Project Phoenix, to continue the NASA targeted search program using the orphaned NASA spectrometer hardware and whatever telescope time could be purchased from donations to the SETI Institute. In 1995, observations resumed at the Parkes radio telescope in Australia, and subsequently a telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia, and the 300 metre dish at Arecibo Observatory in Puerto Rico. The project continued through 2004.

What should SETI look like in the 21st century? Much had changed since the early days in the 1960s and 1970s. Digital electronics and computers had increased in power a billionfold, not only making it possible to scan a billion channels simultaneously and automatically search for candidate signals, but to combine the signals from a large number of independent, inexpensive antennas (essentially, glorified satellite television dishes), synthesising the aperture of a huge, budget-busting radio telescope. With progress in electronics expected to continue in the coming decades, any capital investment in antenna hardware would yield an exponentially growing science harvest as the ability to analyse its output grew over time. But to take advantage of this technological revolution, SETI could no longer rely on piggyback observations, purchased telescope time, or allocations at the whim of research institutions: “SETI needs its own telescope”—one optimised for the mission and designed to benefit from advances in electronics over its lifetime.

In a series of meetings from 1998 to 2000, the specifications of such an instrument were drawn up: 350 small antennas, each 6 metres in diameter, independently steerable (and thus able to be used all together, or in segments to simultaneously observe different targets), with electronics to combine the signals, providing an effective aperture of 900 metres with all dishes operating. With initial funding from Microsoft co-founder Paul Allen (and with his name on the project, the Allen Telescope Array), the project began construction in 2004. In 2007, observations began with the first 42 dishes. By that time, Paul Allen had lost interest in the project, and construction of additional dishes was placed on hold until a new benefactor could be found. In 2011, a funding crisis caused the facility to be placed in hibernation, and the observatory was sold to SRI International for US$ 1. Following a crowdfunding effort led by the SETI Institute, the observatory was re-opened later that year, and continues operations to this date. No additional dishes have been installed: current work concentrates on upgrading the electronics of the existing antennas to increase sensitivity.

Jill Tarter retired as co-director of the SETI Institute in 2012, but remains active in its scientific, fundraising, and outreach programs. There has never been more work in SETI underway than at the present. In addition to observations with the Allen Telescope Array, the Breakthrough Listen project, funded at US$ 100 million over ten years by Russian billionaire Yuri Milner, is using thousands of hours of time on large radio telescopes, with a goal of observing a million nearby stars and the centres of a hundred galaxies. All data are available to the public for analysis. A new frontier, unimagined in the early days of SETI, is optical SETI. A pulsed laser, focused through a telescope of modest aperture, is able to easily outshine the Sun in a detector sensitive to its wavelength and pulse duration. In the optical spectrum, there’s no need for fancy electronics to monitor a wide variety of wavelengths: all you need is a prism or diffraction grating. The SETI Institute has just successfully completed a US$ 100,000 Indiegogo campaign to crowdfund the first phase of the Laser SETI project, which has as its ultimate goal an all-sky, all-the-time search for short pulses of light which may be signals from extraterrestrials or new natural phenomena to which no existing astronomical instrument is sensitive.

People often ask Jill Tarter what it’s like to spend your entire career looking for something and not finding it. But she, and everybody involved in SETI, always knew the search would not be easy, nor likely to succeed in the short term. The reward for engaging in it is being involved in founding a new field of scientific inquiry and inventing and building the tools which allow exploring this new domain. The search is vast, and to date we have barely scratched the surface. About all we can rule out, after more than half a century, is a Star Trek-like universe where almost every star system is populated by aliens chattering away on the radio. Today, the SETI enterprise, entirely privately funded and minuscule by the standards of “big science”, is strongly coupled to the exponential growth in computing power and hence, roughly doubles its ability to search around every two years.

The question “are we alone?” is one which has profound implications either way it is answered. If we discover one or more advanced technological civilisations (and they will almost certainly be more advanced than we—we’ve only had radio for a little more than a century, and there are stars and planets in the galaxy billions of years older than ours), it will mean it’s possible to grow out of the daunting problems we face in the adolescence of our species and look forward to an exciting and potentially unbounded future. If, after exhaustive searches (which will take at least another fifty years of continued progress in expanding the search space), it looks like we’re alone, then intelligent life is so rare that we may be its only exemplar in the galaxy and, perhaps, the universe. Then, it’s up to us. Our destiny, and duty, is to ensure that this spark, lit within us, will never be extinguished.

Scoles, Sarah. Making Contact. New York: Pegasus Books, 2017. ISBN 978-1-68177-441-1.

This is a SETI Institute seminar with Jill Tarter and Sarah Scoles discussing the book, SETI, Tarter’s career, and future prospects for SETI, including the Laser SETI project.

Here is Jill Tarter’s 2009 TED talk which figures in the book. This is the debut of the new Jill Tarter without slides with dozens of bullet points. Tarter was the winner of the 2009 TED Prize.

This a lecture by Jill Tarter in 2014 at NASA Ames, “Searching for ET: An Investment in Our Long Future”:

An October, 2016 SETI Talk by Eliot Gillum describes the Laser SETI project:

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There are 25 comments.

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  1. Judge Mental, Secret Chimp Member

    Are they still doing crowd sourcing on processing the captured data? I remember running their screen saver for a few years, where they would send out data packets to be processed, and then capture the results.

    • #1
    • September 2, 2017, at 11:11 AM PDT
    • 2 likes
  2. Randy Webster Member

    I used to have seven or eight PC’s running the SETI software.

    This reminds me of a quote from some general I read somewhere “We’re alone, or we’re not. Either way, it boggles the mind.”

    • #2
    • September 2, 2017, at 11:35 AM PDT
    • 3 likes
  3. Gary McVey Contributor
    Gary McVey Joined in the first year of Ricochet Ricochet Charter Member

    Coincidentally, in the US this weekend a restored version of “Close Encounters of the Third Kind” is playing in about 900 theaters. It’s probably hard for younger Ricochetti to imagine the level of hype that picture got when released in late 1977. Partly this was because “Star Wars” had opened six months earlier and become an unprecedented box office phenomenon, so the expectations were the director of “Jaws” should easily be able to top it. (He didn’t.)

    But partly it was a function of Columbia Pictures’ buildup campaign, rather unusual in that they sought the endorsement of prestigious figures like Ray Bradbury, the Dalai Lama, Carl Sagan and the secretary general of the United Nations. In short, it was a pretentious campaign meant to convince the public that this was more than just a movie, but something akin to a religious experience. Widespread SETI publicity in the Seventies was part of that background.

    It has been speculated since that Spielberg, like most people, underestimated how long it would take to identify a provable extraterrestrial signal; that he wanted to be proven to be a prophet when that day came, be it in 1979 or 1982 or 1985.

    • #3
    • September 2, 2017, at 11:45 AM PDT
    • 5 likes
  4. John Walker Contributor
    John Walker

    Judge Mental (View Comment):
    Are they still doing crowd sourcing on processing the captured data? I remember running their screen saver for a few years, where they would send out data packets to be processed, and then capture the results.

    This is the [email protected] project, which has been run by UC Berkeley since 1999. The project is still running, and you can download and run the software. It has since been extended into an open infrastructure which allows running other computationally-intense tasks in the background.

    In the 1990s and early 2000s, most personal computers, when not processing user tasks, simply whiled away their time in an “idle loop” which did nothing. Thus, it made sense to replace the idle loop with a task that mopped up all of that otherwise wasted compute time to do something useful. In the late ’80s I spent three years of computer time trying to figure out whether the number 196 ever formed a palindrome!

    These days, most computers have intelligent power management, which means that when they’re idle, rather than just running what amounts to a:

    heck: goto heck;

    loop, they reduce the clock speed and power down, which doesn’t just lower energy consumption, it reduces the heat generated by the processor, which in turn reduces cooling requirements and increases component life. With such machines, a compute-bound background task or screen saver makes less sense, and as a result programs like [email protected] are less frequently used today.

    • #4
    • September 2, 2017, at 11:58 AM PDT
    • 6 likes
  5. Scott Abel Inactive

    Judge Mental (View Comment):
    Are they still doing crowd sourcing on processing the captured data? I remember running their screen saver for a few years, where they would send out data packets to be processed, and then capture the results.

    I’m still doing it, since 2001. As John explained.

    • #5
    • September 2, 2017, at 2:44 PM PDT
    • 2 likes
  6. Bob Wainwright Member

    John, Here’s a real dumb question..

    You mention that there’s basically an infinite number of possible frequencies a signal could be sent on, so we could be listening in the right direction but not be on the right frequency.

    Isn’t there some way to have a receiver that simply picks up everything, regardless of frequency? After all, the signal is passing through, so why can’t it be detected regardless of what frequency the receiver is tuned to?

    • #6
    • September 2, 2017, at 6:14 PM PDT
    • 2 likes
  7. Randy Webster Member

    • #7
    • September 2, 2017, at 7:29 PM PDT
    • 3 likes
  8. John Walker Contributor
    John Walker

    Bob Wainwright (View Comment):
    Isn’t there some way to have a receiver that simply picks up everything, regardless of frequency? After all, the signal is passing through, so why can’t it be detected regardless of what frequency the receiver is tuned to?

    Radio signals have traditionally been thought of as having a single principal frequency, or “carrier wave”, which contains most of the energy of the transmission. Information is transmitted in a variety of ways: by turning the carrier wave off and on, as when transmitting Morse or teletype code, by varying the intensity of the carrier (amplitude modulation, or AM radio), or shifting its frequency up and down through a range which is small compared to the carrier frequency (frequency modulation, or FM radio). This is because it is very easy to generate a carrier signal with a tuned circuit, and to pick it out of the background noise with another tuned circuit set to the same frequency as the carrier. When you “tune” a simple radio, you’re adjusting a tuned circuit to correspond to the carrier frequency of the transmitter to which you wish to listen.

    This is a tremendous simplification of the set of all possible electromagnetic signals. A pure carrier wave has the waveform of a simple sine wave, but it’s possible for an electromagnetic signal to have any waveform whatsoever. It is possible to represent an arbitrary waveform as the sum of a series of sine waves by means of a Fourier transform, decomposing the signal into a spectrogram. A device which does this is, not surprisingly, called a spectrograph. SETI observations have mostly used electronic spectrographs operating in the microwave band (where signals propagate efficiently over interstellar distances and aren’t absorbed by the Earth’s atmosphere). These spectrographs have, over time, grown from the hundred-channel unit of project SERENDIP to the billion channel spectrum analysers used in current work. Inherent in all of this work, dating back to Project Ozma in 1960, is that the most likely alien signal will be a “beacon” consisting of a carrier wave on a single, precisely-controlled frequency. Such a signal is economical to generate and transmit, is easily distinguished from background noise, and, importantly, is not generated by any known natural process. Detecting such a signal would mean that it is either artificially-generated or the result of a novel astrophysical source never before observed.

    But there is another way to go about receiving a radio signal. With sufficiently high performance electronics (something which was only a dream until recently), it is possible to build a “software-defined radio”. This dispenses entirely with tuned circuits, and simply connects the antenna to an analogue-to-digital converter, which produces a digital signal representing the waveform sampled at a sufficiently high rate to represent it faithfully. Software then processes these waveform data with algorithms which extract the signal from them, depending upon how it is encoded. Running the sampled waveform through a Fourier transform algorithm, for example, produces a spectrogram of the signal, but many other transformations and modulations are possible.

    Software-defined radio is now practical for carrier frequencies up to those used in amateur radio and military communications, but we’re not yet at the point where it can operate in the microwave bands examined by most SETI projects. The advent of software-defined radio at SETI frequencies is one of the anticipated technological breakthroughs that will dramatically increase the performance of SETI without any need to upgrade the antenna hardware.

    It should be noted that SETI researchers are not unanimous in assuming a narrow-band beacon is the most effective signal for interstellar communications. That assumption dates from the days when such signals were the only kind we could easily produce and detect, which was long before the advent of technologies such as spread-spectrum and broadband communications. In the following talk, James Benford, who knows a thing or two about microwave communication, argues that a cost-optimised interstellar beacon is more likely to be a pulsed or spread spectrum transmission, and that by searching exclusively for narrow-band beacons we may be looking in the wrong place. If this view is correct, the advent of software-defined radio will be extremely important in searching for such signals.

    • #8
    • September 3, 2017, at 4:27 AM PDT
    • 6 likes
  9. Bob Wainwright Member

    Thanks so much John.

    • #9
    • September 3, 2017, at 6:39 AM PDT
    • 3 likes
  10. Jack Sarfatti Inactive

    Historical note. Phil Morrison was my undergrad advisor at Cornell in 1959 and I was taking classes from him when he was working on the paper cited above.

    • #10
    • September 3, 2017, at 10:48 AM PDT
    • 3 likes
  11. Dan Hanson Thatcher
    Dan Hanson Joined in the first year of Ricochet Ricochet Charter Member

    While radio SETI is important, I think SETI may have more luck looking for artifacts of civilization rather than communication signals.

    We are in our infancy when it comes to communication technology. It is entirely possible that broadcast radio emissions are a tiny blip in the lifespan of a civilization, We ourselves are in the process of going cosmically ‘dark’ as we move away from powerful broadcast signals towards fiber and cable. Tuned narrowband communications are very rapidly giving way to spread spectrum, encrypted communications which can be very hard to pick out from noise in a foreign signal. And we’ve only been at the point where we can communicate over large distances for a tiny fraction of our civilized existence, which in turn is only a tiny fraction of the age of the universe.

    With telescopes like the James Webb observatory coming online, and with increasingly large telescopes on earth with adaptive optics, it seems more likely that we will discover civilizations by looking for pollution in the atmospheres of exoplanets, Dyson spheres around stars, perhaps the signatures of relativistic spaceships or beamed power used to accelerate them, etc. Communication technologies may change rapidly, but huge civilizations require huge amounts of energy or make huge changes to their solar systems, and that’s the kind of thing we might be able to detect.

    • #11
    • September 3, 2017, at 5:02 PM PDT
    • 4 likes
  12. Randy Webster Member

    Dan Hanson (View Comment):
    Dyson spheres around stars,

    Do you think that Dyson spheres are a real possibility?

    • #12
    • September 3, 2017, at 5:21 PM PDT
    • 1 like
  13. Trink Coolidge
    Trink Joined in the first year of Ricochet Ricochet Charter Member

    Dan Hanson (View Comment):
    With telescopes like the James Webb observatory coming online, and with increasingly large telescopes on earth with adaptive optics, it seems more likely that we will discover civilizations by looking for pollution in the atmospheres of exoplanets, Dyson spheres around stars, perhaps the signatures of relativistic spaceships or beamed power used to accelerate them, etc. Communication technologies may change rapidly, but huge civilizations require huge amounts of energy or make huge changes to their solar systems, and that’s the kind of thing we might be able to detect.

    Fascinating. Thank you.

    • #13
    • September 3, 2017, at 5:24 PM PDT
    • 3 likes
  14. Benjamin Glaser Inactive

    My dad worked at NRAO in Green Bank, WV back when SETI was active on the 40m telescope. Those guys were pretty fun to talk to as a 17 year-old high school senior.

    • #14
    • September 3, 2017, at 6:20 PM PDT
    • 2 likes
  15. Judge Mental, Secret Chimp Member

    Dan Hanson (View Comment):
    While radio SETI is important, I think SETI may have more luck looking for artifacts of civilization rather than communication signals.

    We are in our infancy when it comes to communication technology. It is entirely possible that broadcast radio emissions are a tiny blip in the lifespan of a civilization, We ourselves are in the process of going cosmically ‘dark’ as we move away from powerful broadcast signals towards fiber and cable. Tuned narrowband communications are very rapidly giving way to spread spectrum, encrypted communications which can be very hard to pick out from noise in a foreign signal. And we’ve only been at the point where we can communicate over large distances for a tiny fraction of our civilized existence, which in turn is only a tiny fraction of the age of the universe.

    With telescopes like the James Webb observatory coming online, and with increasingly large telescopes on earth with adaptive optics, it seems more likely that we will discover civilizations by looking for pollution in the atmospheres of exoplanets, Dyson spheres around stars, perhaps the signatures of relativistic spaceships or beamed power used to accelerate them, etc. Communication technologies may change rapidly, but huge civilizations require huge amounts of energy or make huge changes to their solar systems, and that’s the kind of thing we might be able to detect.

    “The Ringworld is unstable!”

    • #15
    • September 3, 2017, at 7:21 PM PDT
    • 4 likes
  16. Dan Hanson Thatcher
    Dan Hanson Joined in the first year of Ricochet Ricochet Charter Member

    Randy Webster (View Comment):

    Dan Hanson (View Comment):
    Dyson spheres around stars,

    Do you think that Dyson spheres are a real possibility?

    A Dyson Sphere, probably not. An actual solid sphere around the sun would not be gravitationally stable. But the modern conception of a Dyson sphere is more like a Dyson swarm – a vast collection of solar collectors, habitats or other artifacts, each disconnected from the others and in its own orbit. Put enough of them in orbit around the star, and we could detect it as a dimming of the star, coupled with an increase in infrared radiation that shouldn’t exist for a star of that type.

    For example, you may have heard of Tabby’s Star, which is a star that The Kepler mission was observing, looking for planetary transits that cause slight dimming of the star when the planet passes in front. That’s how we have detected most of our exoplanets. But Tabby’s star is strange – it has weird, non-periodic transits much bigger than a planet should be able to cause. And the transits are oddly-shaped, which would not be the case for a transiting spherical object.

    In addition, Tabby’s star has been constantly dimming for decades, which is unheard of in a main sequence star. Now, no one is saying that it’s aliens, but to this point we do not have a satisfactory explanation for what is going on there. But this is exactly the type of signature you might see if a civilization were in the process of building out a giant dyson swarm. Other features are missing, howver, such as an increase in infra-red radiation,

    Whatever it is, it’s something rare as Kepler has looked at over 70,000 stars and we have not seen another one remotely similar.

    We now have a catalog of thousands of exoplanets that Kepler has discovered. Now that we know where they are and when they will transit, we can begin to look at how the star’s spectra changes when the planet passes in front. With the new generation of telescopes coming online, we should soon be able to measure the composition of the atmospheres of earth-like planets in the habitable zones of those stars. If we find planets with oxygen-rich atmospheres or other chemicals like methane, it will be a strong marker for life. We can then target those planets for more detailed measurements.

    My own guess is that life is relatively common in the universe, but intelligent, technological civilizations may be extremely rare. In that case, my money is on us discovering life somewhere else in the cosmos long before we pick up communications from ET.

    • #16
    • September 3, 2017, at 7:30 PM PDT
    • 4 likes
  17. Trink Coolidge
    Trink Joined in the first year of Ricochet Ricochet Charter Member

    Dan Hanson (View Comment):
    My own guess is that life is relatively common in the universe, but intelligent, technological civilizations may be extremely rare. In that case, my money is on us discovering life somewhere else in the cosmos long before we pick up communications from ET.

    Dang. It’s been the main event on my bucket list. First contact. Hubby and I may not have but a couple decades to go yet. Dang. So we shouldn’t hold our breath, I guess :(

    • #17
    • September 3, 2017, at 7:39 PM PDT
    • 2 likes
  18. Randy Webster Member

    Dan Hanson (View Comment):
    With the new generation of telescopes coming online, we should soon be able to measure the composition of the atmospheres of earth-like planets in the habitable zones of those stars.

    Incredible. Thanks, Dan.

    • #18
    • September 3, 2017, at 10:10 PM PDT
    • 2 likes
  19. John Walker Contributor
    John Walker

    Dan Hanson (View Comment):
    For example, you may have heard of Tabby’s Star, which is a star that The Kepler mission was observing, looking for planetary transits that cause slight dimming of the star when the planet passes in front. That’s how we have detected most of our exoplanets. But Tabby’s star is strange – it has weird, non-periodic transits much bigger than a planet should be able to cause. And the transits are oddly-shaped, which would not be the case for a transiting spherical object.

    I’ve always expected that if and when we detect intelligent aliens it will be a) in some part of the observational phase space we’ve opened up looking for something else entirely and b) obvious in retrospect that we’d made many “pre-discovery observations” which we didn’t know how to interpret at the time.

    The discovery of pulsars is an excellent example of this: as soon as radio astronomy observations with high time resolution began to be made, we discovered something so strange that nobody could, at the time, think of a natural process that could account for it. In that case, it turned out to be spinning neutron stars rather than aliens, but it’s an example of how when you look in a new place, you often find things you never imagined existed.

    Tabby’s star (KIC 8462852) is another example: it’s the result of the Kepler spacecraft conducting a long-term staring survey of transits on a large number of stars. Once again, we looked in a corner of the observational phase space we’d never probed before, and something distinctly odd popped out. The jury’s still out on this one.

    Another mystery, less well known to non-specialists, is the “fast radio bursts”. First detected in 2007, they are millisecond-length pulses in the radio band which seem to come from distant sources at extragalactic distances. Their discovery was accidental, and exploration of them is opening up another part of the phase space: transient radio events distributed across the whole sky. The first observations seemed never to repeat, but more recently a source (FRB 121102) has been found which does repeat. Nobody knows the cause of these bursts. A recent paper has noted that the properties of fast radio bursts are almost precisely what you’d expect from transient observations of microwave-propelled light sails used by advanced extragalactic civilisations to propel interplanetary or interstellar craft as leakage from the propulsion beam happens to sweep across the Earth.

    • #19
    • September 4, 2017, at 1:03 AM PDT
    • 5 likes
  20. YouCantMeanThat Coolidge

    Randy Webster (View Comment):
    This reminds me of a quote from some general I read somewhere “We’re alone, or we’re not. Either way, it boggles the mind.”

    ^That^

    (Why I read Ricochet — The occasional word from people who know about what they are talking (as opposed to the bloviating about current events, about which no one actually knows anything).)

    In my own unschooled rumination on seti (not to be confused with SETI) I was stuck at the point of, “If they’re civilized, the BEMs (more politely LGMs) must have radio.” Several posts have given thoughtful work-arounds on that. But the one I would toss out is the fact that potential sources being a bazillion light years away means that ANY observation of which we are capable is observing conditions a bazillion years ago. Thus, if there is any correlation between the appearance of us and our development of technology coupled with a sufficient disconnect from the lower levels of Maslow’s Hierarchy to permit serious seti, and the age of the galaxy and/or the universe, it may simply be too soon to see anything but possibly the BEM equivalent of the stone age, or less.

    • #20
    • September 5, 2017, at 7:09 AM PDT
    • 1 like
  21. John Walker Contributor
    John Walker

    YouCantMeanThat (View Comment):
    But the one I would toss out is the fact that potential sources being a bazillion light years away means that ANY observation of which we are capable is observing conditions a bazillion years ago.

    This is a common misconception as regards most current and past SETI projects. With the exception of a very few and extremely limited searches for signals from other galaxies and star clusters, which would require such power to generate that they could be sent only by a civilisation so far advanced compared to our own that we could scarcely imagine their capabilities or motives (the energy needed to send such a signal would require, at the minimum, harnessing the entire energy output of one or more stars), almost all SETI observations are sensitive only to signals from a distance of around 1000 light years, which includes around one million stars. A signal from a civilisation at this distance would have taken at most 1000 years to reach Earth, so the sender need only be in advance of terrestrial technology by that amount.

    This is a tiny sample of the galaxy—there are around two hundred billion stars in the Milky Way galaxy, so the stars we can observe with current SETI technology is 1/200000 of those in the galaxy, or 0.0005%.

    The estimation of a maximum detection range of 1000 light years makes the assumption that the signals we’re looking for are those we could generate with our own existing technology and with a budget comparable to “big science” projects such as the Large Hadron Collider or the International Space Station. If the sending civilisation were transmitting a stronger signal, this would increase the range at which it can be detected, but only slowly due so the inverse square law (if you double the distance, you need a signal four times stronger to remain detectable).

    There are stars similar to the Sun which are billions of years older, so a gap of 1000 years in technology is no barrier to finding another communicating civilisation. One key factor in determining how many communicating civilisations exist within a range where we can detect them is how long each civilisation transmits its beacon. Even if civilisations are common, if each transmits for much less than 10,000 years, it’s unlikely that two will overlap within a 1000 light year radius. So one of the assumptions of the SETI endeavour is the optimistic assumption that once a civilisation develops the technology to communicate, it will remain at that level of technology for a long time compared to recorded human history.

    It’s worth noting that for our own species, this “longevity” parameter in the Drake equation is currently zero—we have never yet deliberately transmitted a signal which would be detectable by a SETI search conducted by beings in another star system.

    • #21
    • September 5, 2017, at 7:50 AM PDT
    • 2 likes
  22. YouCantMeanThat Coolidge

    John Walker (View Comment):
    we have never yet deliberately transmitted a signal which would be detectable by a SETI search conducted by beings in another star

    Most excellent. But “deliberately” is a very big word; are we not radiating, rather promiscuously, signals that would be interpreted as “intelligent?” Even back episodes of, say, The Beverly Hillbillies?” More problematic is that thousand year figure; we’ve not had a civilization last nearly that long, much less a technology, and the returns are from from being counted on the question of whether we are capable. You may argue that the latter is more political than scientific, but it is no less real.

    • #22
    • September 5, 2017, at 8:12 AM PDT
    • 1 like
  23. Judge Mental, Secret Chimp Member

    YouCantMeanThat (View Comment):

    John Walker (View Comment):
    we have never yet deliberately transmitted a signal which would be detectable by a SETI search conducted by beings in another star

    Most excellent. But “deliberately” is a very big word; are we not radiating, rather promiscuously, signals that would be interpreted as “intelligent?” Even back episodes of, say, The Beverly Hillbillies?” More problematic is that thousand year figure; we’ve not had a civilization last nearly that long, much less a technology, and the returns are from from being counted on the question of whether we are capable. You may argue that the latter is more political than scientific, but it is no less real.

    But it’s not as if we have one big transmitter beaming The Beverley Hillbillies. There are thousands, each sending out a different signal. I have to guess that’s going to work out to something like white noise. Guessing again, I’m betting that is going to be similar to the radio noise produced by stars.

    • #23
    • September 5, 2017, at 8:18 AM PDT
    • Like
  24. Judge Mental, Secret Chimp Member

    Judge Mental (View Comment):

    YouCantMeanThat (View Comment):

    John Walker (View Comment):
    we have never yet deliberately transmitted a signal which would be detectable by a SETI search conducted by beings in another star

    Most excellent. But “deliberately” is a very big word; are we not radiating, rather promiscuously, signals that would be interpreted as “intelligent?” Even back episodes of, say, The Beverly Hillbillies?” More problematic is that thousand year figure; we’ve not had a civilization last nearly that long, much less a technology, and the returns are from from being counted on the question of whether we are capable. You may argue that the latter is more political than scientific, but it is no less real.

    But it’s not as if we have one big transmitter beaming The Beverley Hillbillies. There are thousands, each sending out a different signal. I have to guess that’s going to work out to something like white noise. Guessing again, I’m betting that is going to be similar to the radio noise produced by stars.

    Put that on top of most of the signals not being powerful enough to go very far, in terms of being heard against the background noise.

    • #24
    • September 5, 2017, at 8:22 AM PDT
    • Like
  25. John Walker Contributor
    John Walker

    YouCantMeanThat (View Comment):
    Most excellent. But “deliberately” is a very big word; are we not radiating, rather promiscuously, signals that would be interpreted as “intelligent?” Even back episodes of, say, The Beverly Hillbillies?”

    This is what, in the SETI community, is called “leakage radiation”: transmissions which propagate into space that were not intended as a beacon to other civilisations. Significant leakage from the Earth only dates from the years after World War II, when television broadcasting in the VHF and later UHF bands became common and high-power military radars were deployed for anti-aircraft surveillance and ballistic missile warning. (Earlier radio broadcasts were at frequencies which are bent by the Earth’s ionosphere and do not escape into space in large quantities.)

    The Earth is increasingly going “radio silent” as high power broadcasting is being replaced by cable and fibre optic distribution and satellite broadcasting. Unlike a terrestrial radio transmitter which leaks its signals along the horizon, a communication satellite aims its antennas at the Earth and leaks very little signal to space. Military radars continue to be used, but their signals are intermittent and detecting them would require the listener to searching at just the right place and right time.

    The fact is that if there were planets radiating leakage energy to the extent the Earth presently does, none of the SETI searches to date or presently planned would have detected it. That would require at least a massive antenna array as envisioned by Project Cyclops plus the luck to happen to be listening when the beam from one of the leakage sources happened to sweep past the Earth. And even so, the distance at which even so grandiose a system (recall that the budget estimate for Cyclops was comparable to the Apollo project) could detect Earth-scale leakage was estimated to be less than 100 light years, within which there are around 150,000 stars.

    • #25
    • September 5, 2017, at 8:31 AM PDT
    • 2 likes

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