by Paul Gilster | Nov 14, 2016 | Culture and Society |
Think fast. You’ve only got a day or so to work on this. You’ve been asked to come up with a plausible way of getting a fictional crew from one star to another, but laser sails and fusion rockets won’t do. The target might be thousands of light years away, so you have to be thinking faster-than-light. Maybe Miguel Alcubierre comes to mind, or perhaps a wormhole, but a nod in either direction isn’t enough. You’re being asked for a high level of detail, and you’d better have some serious equations available to show you’re not just blowing smoke.
As you might guess, the question relates to the Denis Villeneuve film Arrival, which Paramount released in the U.S. last Friday following its premiere at the Venice Film Festival. No spoilers here, just an entertaining tale. For the person who was asked to dream up fast interstellar transport was Stephen Wolfram, whose public relations people had received a request from the filmmakers to upgrade the science in the film, which was based on a 1998 short story by the brilliant Ted Chiang, a Nebula Award winning short story writer.
As to Wolfram, he heads up Wolfram Research and is the chief designer of both technical computing engine Mathematica and the Wolfram Alpha online presence. In what I might jokingly refer to as his ‘spare time’ he is the author of the recent A New Kind of Science, written during breaks from his work on knowledge-based programming, the latter being an expansion of Mathematica into what is now called the Wolfram Language.
Wolfram, in other words, is a formidable source when it comes to ideas pushing out to the edges of what we know. Intrigued by the challenge of Arrival, Wolfram and son Christopher traveled to Montreal to meet with the film crew. Soon both men were involved with analysis and computations as they turned questions from the director into Wolfram Language code and visualizations. But time was short, and the biggest challenge was coming up with a theory of interstellar space flight in the course of a single evening.
I don’t know if Wolfram is a movie buff or not, but I’d imagine that working this closely with actors and writers and everyone else on the site is enough to make him one. In any case, he’s keen to avoid giving away anything about the film — for that you have to see it — so you can go to his essay Quick, How Might the Alien Spacecraft Work? without concern that it will deflect your enjoyment of a film that is beginning to get a pretty solid buzz (I suspect our resident movie critic Larry Klaes is going to turn up with an essay about this movie, too).
What we get here is only an introduction into the material Wolfram supplied the filmmakers, but it’s intriguing in its own right. It draws from his own speculations about fundamental physics and the lowest level structure of space itself, the idea being that it is, in his words, ‘a network of nodes, where all that’s defined is connectivity.’ Thus space as we perceive it emerges as a large-scale feature even though it’s made up of discrete nodes. He likens this to water, which is made up of discrete molecules but ‘emerges’ as oceans and rivers.
The three-dimensional network underlying the universe, Wolfram supposes for the sake of his model, is made up mostly of local connections, while a few are long-range connections, which correspond to quantum entanglement. The trick is somehow to exploit these long-range connections, which involves disconnecting the outside of the ship from the rest of the network.
This calls for a form of matter that is not made from standard elementary particles, but as Wolfram says, “might be like a giant crystal formed directly from connections that make up space.” Thus the skin of the imagined ship is a dynamic metamaterial, and it is this boundary layer material that creates the needed interaction with the outside universe. And yes, it’s unobtainium, but remember, we’re in a fictional universe studying alien technologies.
We can’t go any further without going into the movie itself, but what comes across in Wolfram’s lively essay is the author’s sheer enjoyment at creating a self-consistent theory that could be referenced in the script. Numerous ideas for science fiction dialogue ensued, most of them not necessary in the actual film, but enlivening in their own right:
Here are a few of the ones that (probably for the better) didn’t make it into the final script. “The whole ship goes through space like one giant quantum particle.” “The aliens must directly manipulate the spacetime network at the Planck scale.” “There’s spacetime turbulence around the skin of the ship.” “It’s like the skin of the ship has an infinite number of types of atoms, not just the 115 elements we know” (that was going to be related to shining a monochromatic laser at the ship and seeing it come back looking like a rainbow). It’s fun for an “actual scientist” like me to come up with stuff like this. It’s kind of liberating. Especially since every one of these science fiction-y pieces of dialogue can lead one into a long, serious, physics discussion.
Wolfram says he got involved in Arrival because Hollywood films all too often don’t get the science input they need, a fact he attributes to directors being more attuned to human conflict and character development than the ‘science texture’ of their movies. But of course we have seen some films with an active science advisor, like Kip Thorne in the recent Interstellar, who conjured up its black hole effects with Mathematica. And (I hadn’t known this), Marvin Minsky worked on artificial intelligence issues for 2001: A Space Odyssey, while mathematician Manjul Bhargava spent years helping to bring The Man Who Knew Infinity to the screen, with careful attention to the math. Agreed, that one isn’t exactly science fiction, being a study of Indian mathematician Srinivasa Ramanujan.
Even so, science fiction in Hollywood hasn’t been known for its history of verisimilitude. Wolfram again:
When I watch science fiction movies I have to say I quite often cringe, thinking, “someone’s spent $100 million on this movie?—?and yet they’ve made some gratuitous science mistake that could have been fixed in an instant if they’d just asked the right person.” So I decided that even though it was a very busy time for me, I should get involved in what’s now called Arrival and personally try to give it the best science I could.
There’s a lot more than starship talk in Wolfram’s essay, especially on establishing communications with an alien intelligence (Wolfram starts with cellular automata), the similarities between software design and movie production, and the possible uses of gravitational waves (massive, spinning non-spherical objects produce them). I keep thinking that with people like Stephen Wolfram involved, the science standards in our films are bound to be on the uptrend presaged by Kip Thorne’s presence in Interstellar.
That could lead to some interesting choices of scripts as we tap the vast store of written science fiction, all too little exploited, for film plots with a genuinely scientific underpinning. Countless short stories and novels form a rich tradition growing out of the science fiction magazines and emerging in the late 20th Century as a vibrant literature in its own right. It’s time Hollywood embarked upon a much deeper acquaintance with this material.
by Paul Gilster | Nov 11, 2016 | Deep Sky Astronomy & Telescopes |
A newly discovered brown dwarf dubbed OGLE-2015-BLG-1319 is significant on several fronts, not the least of which is how it was found. Not only are we dealing here with another instance of gravitational microlensing, where the light of a background star is affected by a foreground object in ways that give us information about the closer star, but this instance of microlensing saw two space telescopes working together to make sense of the event, the first time a microlensing event has been observed by two space telescopes and from the ground.
The space-based instruments in question are the Spitzer and Swift telescopes, whose combined observations give us different magnification patterns rising from the same event. Spitzer observed the binary system containing the brown dwarf in July of 2015 from its perch about 1 AU away from the Earth. Swift, in low Earth orbit, also saw the system in late June of that year, marking its first microlensing observation. The first notification of the event came from the Optical Gravitational Lens Experiment (OGLE) in Chile, and it was also observed by the Microlensing Observations in Astrophysics (MOA) collaboration in New Zealand.
Image: This illustration depicts a newly discovered brown dwarf, an object that weighs in somewhere between our solar system’s most massive planet (Jupiter) and the least-massive-known star. This brown dwarf was discovered when it and its star passed between Earth and a much more distant star in our galaxy. This created a microlensing event, where the gravity of the system amplified the light of the background star over the course of several weeks. Credit: NASA/JPL-Caltech.
Combining the data and including observations from ground-based instruments allows scientists to make a call on the mass of the brown dwarf, between 30 and 65 Jupiter masses. The brown dwarf orbits a K-class star with about half the mass of the Sun. But focus on this: One of two possible distances between brown dwarf and star is 0.25 AU, which would put the object in what is known as the brown dwarf desert. The latter is a reference to the fact that stars of about the Sun’s mass rarely have a brown dwarf orbiting within 3-5 AU.
We don’t know for sure because there are two solutions to the distance question, the second being 40-52 AU. The paper notes that the Swift satellite is not distant enough from the Earth to allow for a separate measurement of the microlensing parallax, which would have made it possible to refine the distance measurement further. We get two solutions for the projected separation of brown dwarf and star, a well-known problem called close-wide degeneracy in which the perturbation patterns of close and wide objects can appear similar.
But if the 0.25 AU distance is correct, it would add to mounting evidence that the so-called ‘desert’ may be a mirage. For it turns out that OGLE-2015-BLG-1319 is hardly the first brown dwarf found through microlensing. In fact, there have been 15 published microlensing events involving brown dwarfs before this one, including one that hosted a planet, ten brown dwarfs around main sequence stars (with nine around M-dwarfs and one around a G-K class star), two binary brown dwarfs and two isolated brown dwarfs. In about half of these we also have questions about the distance between brown dwarf and star, but note this from the paper:
…the accumulation of detections suggests that BDs around main-sequence stars are not rare at separations of 0.5-20 AU, where microlensing is sensitive (this range is larger than for exoplanets due to higher detection sensitivity). This is in contrast to estimates through other techniques, such as radial velocity and transit, who find that BDs are rare (< 1%, Grether & Lineweaver 2006) at closer separations.
What to make of this? The paper continues:
One possible explanation for this difference, as suggested by Shvartzvald et al. (2016), is the different host stars that are mostly probed by each technique — FGK stars by radial velocity and transits versus M stars by microlensing.
Or as lead author Yossi Shvartzvald (JPL) puts it in this JPL news release:
“We want to understand how brown dwarfs form around stars, and why there is a gap in where they are found relative to their host stars. It’s possible that the ‘desert’ is not as dry as we think.”
The paper is Shvartzvald et al., “First simultaneous microlensing observations by two space telescopes: Spitzer & Swift reveal a brown dwarf in event OGLE-2015-BLG-1319,” Astrophysical Journal Vol. 831, No. 2 (7 November 2016). Abstract / preprint.
by Paul Gilster | Nov 10, 2016 | Exoplanetary Science |
Our knowledge of protoplanetary disks around young stars is deepening. This morning we have news of three recently examined disks, each with features of interest because we know so little about how such disks evolve. What we do know is that planets are spawned from the gas and dust we find within them, as we see in the disk below discovered using the SPHERE instrument on the European Southern Observatory’s Very Large Telescope in Chile.
Image: A team of astronomers observed the planetary disc surrounding the star RX J1615, which lies in the constellation of Scorpius, 600 light-years from Earth. The observations show a complex system of concentric rings surrounding the young star, forming a shape resembling a titanic version of the rings that encircle Saturn. Such an intricate sculpting of rings in a protoplanetary disc has only been imaged a handful of times before. Credit: ESO, J. de Boer et al.
The comparison with Saturn is not amiss, for this is a complex system of concentric rings that is uncommon among protoplanetary disks we’ve found so far. While dating such systems is difficult, astronomers believe this disk is a bit less than 2 million years old. Bear in mind that we’re still trying to work out the mechanisms that cause these sculpted effects. They’re surely the result of planets in formation, but it’s worth noting that while the disk around RX J1615 is strikingly regular, we’re just as likely to encounter gaps, voids and spiral arms in such disks.
The work here is from Jos de Boer (Leiden Observatory), who has put the SPHERE instrument to good use. SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) was built as a planet imager, one that would take direct images of exoplanets rather than detecting them through their star’s Doppler shifts or through transits of the planet. An advanced coronagraph, SPHERE blocks out the central star, using a polarimetric differential imaging mode that draws on the fact that the light of the star is unpolarized, while the light scattered by the disk is polarized, allowing sharp images of the disk to be extracted.
Another researcher from Leiden University, Christian Ginski, is behind work on a different young system. The star is HD 97048, about 500 light years from Earth. Here again we see a striking symmetry in the ring system. Four gaps and rings can be found here. But finding any planets that are sculpting this system is not going to be easy, as the paper on this work notes:
We find that nascent planets are one possible explanation for the structures that we are observing. However, given the low planet masses needed to carve out the gaps that we detected, it is unlikely that the planet’s thermal radiation is directly detectable by current generation planet search instruments such as SPHERE or GPI [Gemini Planet Imager]. This conclusion is strengthened by the fact that the gaps are most likely not completely devoid of material and thus any thermal radiation from a planet inside the gap would be attenuated by the remaining dust.
Image: The planetary disc surrounding the star HD 97048 in the constellation of Chameleon, about 500 light-years from Earth. The juvenile disc is formed into concentric rings. This symmetry is in contrast to most protoplanetary systems which contain asymmetrical spiral arms, voids and vortexes. The displayed image is a composite derived from two independent observations that targeted the inner and outer regions of this disc. The central part of the image appears dark because SPHERE blocks out the light from the brilliant central star to reveal the much fainter structures surrounding it. Credit: ESO, C. Ginski et al.
Contrast the two disks above with what Tomas Stolker and colleagues (Anton Pannekoek Institute for Astronomy, the Netherlands) have found. In the image below, we’re looking at HD 135344B, some 450 light years from Earth. Here the disk is obviously asymmetrical, consisting of a central cavity and two spiral arms thought to be the result of planet formation.
And in this system we have a feature that changed noticeably in the months between observing periods. The feature in question is one of the dark streaks that are evidently shadows created by material in motion within the protoplanetary disk. Planetary evolution in real time? That’s what this ESO news release calls it, an indication of the level of detail we can pick out in the inner disk regions of some stars with the SPHERE instrument.
The paper puts the matter this way:
The variable or transient nature of this shadow could be explained by several scenarios, including a local perturbation of the inner disk or an accretion funnel flow from the inner disk onto the star.
Image: The planetary disc surrounding the star HD 135344B, about 450 light-years away. The disc shows prominent spiral arm-like structures. Credit: ESO, T. Stolker et al.
In any case, we’re seeing change within months in this evolving system. And as to the spiral arms themselves:
An explanation for the spiral arms could not be uniquely determined. In the context of linear perturbation theory, the spiral arms are best explained by two protoplanets orbiting exterior of the spiral arms. Protoplanet solutions inside the scattered light cavity seem unlikely because the spiral arm pitch angles would require unphysical disk temperatures.
Understanding how planets shape the disks from which they form is a step forward in planet formation theory, and it’s clear that the environment of young systems like these is complex and varied enough to produce a wide range of outcomes in the evolving disk.
The papers are de Boer et al., “Multiple rings in the transition disk and companion candidates
around RX J1615.3-3255. High contrast imaging with VLT/SPHERE,” Astronomy & Astrophysics 595 (2016), A114 (preprint). On HD 97048, the paper is Ginski et al., “Direct detection of scattered light gaps in the transitional disk around HD 97048 with VLT/SPHERE,” accepted for publication at Astronomy & Astrophysics (preprint). The paper on HD 135344B is Stolker et al., “Shadows cast on the transition disk of HD 135344B,” accepted at Astronomy & Astrophysics (preprint).
by Paul Gilster | Nov 9, 2016 | Astrobiology and SETI |
In the last two days we’ve looked at a discussion of a possible SETI observable, a ‘shielding swarm’ that an advanced civilization might deploy in the event of a nearby supernova. As with Richard Carrigan’s pioneering searches for Dyson swarms in the infrared, this kind of SETI makes fundamentally different assumptions than the SETI we’ve grown familiar with, where the hope is to snag a beacon-like signal at radio or optical wavelengths. So-called ‘Dysonian SETI’ assumes no intent to communicate. It is about observing a civilization’s artifacts.
Both radio/optical SETI and this Dysonian effort are worth pursuing, because we have no idea what the terms of any discovery of an extraterrestrial culture will be. The hope of receiving a deliberate signal carries the enthralling possibility that somewhere there is an Encyclopedia Galactica that we may one day gain access to, or at the least that there is a civilization that wants to talk to us. A Dysonian detection would tell us that civilizations can survive their youth to become builders on a colossal scale, pushing up toward Kardashev levels II and III.
Keeping both SETI tracks engaged is good science. It’s encouraging on the radio front to see that the Parkes radio telescope in Australia has now joined the Green Bank Telescope (West Virginia) and the Automated Planet Finder (Lick Observatory) in SETI observations funded by Breakthrough Listen. A key component of the Breakthrough Initiatives effort (which includes Breakthrough Starshot), Breakthrough Listen has just announced the activation of its SETI project at Parkes with observations of the newly discovered planet around Proxima Centauri.
About this study, several points. First, Parkes marks a welcome expansion of the northern hemisphere efforts. Situated about 20 kilometers north of the town of Parkes in New South Wales, the telescope can observe those parts of the sky that are not visible to its northern counterparts, making it a major component in any comprehensive SETI effort.
Image: The Parkes radio telescope in New South Wales. Credit: CSIRO.
As to Proxima Centauri, we now have an Earth-sized planet orbiting in what appears to be its habitable zone, meaning that temperatures could allow liquid water to exist on its surface. The discovery of Proxima b has enlivened the interstellar community as we examine ways to learn more about it, including the Breakthrough Starshot flyby probe studies. But I think we can agree that the chances of finding a civilization on any particular planet are low.
So says Andrew Siemion, director of the Berkeley SETI Research Center and leader of the Breakthrough Listen science program. And he adds:
“…once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilisation just 4.2 light years away would change everything.”
It was in the same spirit that a number of SETI instruments have been turned to Boyajian’s Star (KIC 8462852), whose unusual light curves have drawn a great deal of attention because we have so far been unable to explain them. In both cases, we have a high-interest target, in the Proxima system because of its sheer proximity to Earth and in the Boyajian’s Star system because one explanation for those light curves is intelligent engineering.
So I am all for examining Proxima Centauri even though I think the real action there will be in one day analyzing its atmosphere for signs of biosignatures. 14 days of commissioning and test observations at Parkes led up to the first observation of Proxima on November 8 (local time). The broader strategy is to continue the SETI effort at radio wavelengths across a wide range of targets, as listed in this Breakthrough Initiatives news release.
- All 43 stars (at south declinations) within 5 parsecs, at 1-15 GHz. Sensitive to the levels of radio transmission at which signals ‘leak’ from Earth-based radar transmitters (with available receivers).
- 1000 stars (south) of all spectral-types (OBAFGKM) within 50 parsecs (1-4 GHz).
- One Million Nearby Stars (south). In 2016-2017, first 5,000 stars; 1 minute exposure (1-4 GHz).
- Galactic plane and Center (1-4 GHz).
- Centers of 100 nearby galaxies (south declinations): spirals, ellipticals, dwarfs, irregulars (1-4 GHz).
- Exotic sources will include white dwarfs, neutron stars, black holes, and other anomalous natural sources (1-4 GHz).
Bear in mind as these efforts proceed that Breakthrough Listen will also be coordinating searches with the FAST (Five hundred meter Aperture Spherical Telescope) in southwest China, exchanging observing plans, search methods and data. Thus we move toward a global SETI effort that can quickly share promising signals for analysis. Data from Parkes and the other Breakthrough Listen telescopes will be made available to the public online.
by Paul Gilster | Nov 8, 2016 | Astrobiology and SETI |
If you’re on the Moon and learn that there has been a major solar eruption, your best course of action is to get inside an appropriate shelter somewhere below ground, where you can be shielded from its effects. By analogy, wouldn’t a future civilization on Earth be able to shield itself from the effects of a supernova or gamma ray burst by burrowing into the planet?
In their paper on stellar explosions and risk mitigation, Milan ?irkovi? and Branislav Vukoti? argue against the idea, which runs into problems on multiple levels. For one thing, while the duration of gamma ray emissions is generally short — on the order of a hundred seconds or less — the pulse of accelerated cosmic rays from a supernova or GRB blast is likely to last much longer, perhaps a matter of months or even years.
Digging to avoid the worst of the effects would take you deep into the ground indeed. The authors cite work showing that you would need to burrow up to 3 kilometers below the surface before the incoming flux would drop to 1% of its initial value. And finally, Earth’s atmosphere could not itself be shielded this way, opening the door to ecological catastrophe.
A system-wide infrastructure involving asteroid mining and perhaps planetary colonies is likewise at risk. For all these reasons, ?irkovi? and Vukoti? think a future or extraterrestrial civilization would choose space-based shielding in its own planetary system as a response to the threat of any nearby stellar explosion. Here the most natural building material is ice, found in great abundance in the outer Solar System. What emerges is the concept of a ‘shielding swarm’ far from the Sun whose bulk density can be adjusted as necessary.
Here the notion of ‘smart dust’ inevitably occurs, which gives us a way of describing the swarm:
…we envision a swarm of particles confined by electromagnetic forces interspersed by smart dust particles controlling the swarm and enabling more precise manipulation, in addition to controlling ionization necessary for the ice particles to be moved around. They could provide essential telemetric information and the data on conditions within the swarm necessary for self-regulation actions. Since various forms of carbon, including fullerenes, is currently thought to be the best material for building smart dust, as well as other nanotechnological applications [89], and the Kuiper Belt objects are carbon-rich, it seems natural to assume that fragmentation of the very same icy body or bodies creating the bulk of the shielding swarm might provide material for construction of smart dust particles as well.
Image: Artist’s impression of a supernova blast. Credit: NASA.
So let’s drop back to the core idea. Assuming a threatening source can be identified and its likely explosion predicted, an advanced civilization could choose the appropriate icy objects and change their orbit to reach the staging area, where construction of the swarm can begin. Such a swarm could itself reduce cosmic ray flux by several factors, while additional active shielding could be provided by the same system of electromagnetic confinement that would be used to manipulate the particles in the swarm during its formation.
Searching for Extraterrestrial Technology
When contemplating what an extraterrestrial civilization might do (or indeed, what we might ourselves do when we reach a sufficient technological level), it’s useful to consider the thought processes involved. Freeman Dyson is relevant here — we are saying that anything we can hypothesize about our own future course should apply to at least some extraterrestrial species. This is how, without understanding the intricacies of a future technology, we can make broad predictions about possible astroengineering and how we might detect it.
Searching for Dyson swarms or spheres is an example of this, the search being motivated by our belief that such a swarm would be an intelligent way of maximizing energy resources for a society around a particular star. The fact that we can imagine it — although we are a long way from being able to do it — means that more advanced cultures have probably run across the same idea, given that it contradicts no physical laws. Thus it is at least worth the attempt to figure out what a Dyson swarm would look like if we stumbled across one in our data.
In a similar way, ?irkovi? and Vukoti? believe, it would be rational for any society to attempt to reduce large-scale risk, in this case in the event of the explosion of a close supernova. Shielding swarms of the kind the duo discuss in their paper are an extrapolation of what we, as a Kardashev 0.7 culture, might do if we had the energy and resources. Nudging forward into Kardashev 1 and beyond, we might look for signs of the presence of such swarms as a potential SETI signature around other stars. The paper suggests these possible observables:
- Planetary size structures with unusually small mass and non-Keplerian motion. In other words, find something the size of a terrestrial planet but with a mass as little as 10-8 Earth mass and suspicion should mount that it is an artifact.
- A swarming shield made predominately of ice may show unusual optical properties like polarization and non-equilibrium temperatures, as well as strong absorption in the far infrared. And this is interesting — a shield that is transiting its star would produce a small optical transit depth but a much larger infrared transit depth.
- Continuing fragmentation of small bodies in a planetary system without accompanying physical causes (collisions), along with anomalous loss of kinetic energy and momentum.
- Unusual observables in a planetary system occurring simultaneously with the last phases of evolution of a nearby supernova progenitor.
Image: The above two photographs are of the same part of the sky. The photo on the left was taken in 1987 during the supernova explosion of SN 1987A, while the right hand photo was taken beforehand. Supernovae are one of the most energetic explosions in nature, equivalent to the power in a 1028 megaton bomb (i.e., a few octillion nuclear warheads). Credit: NASA.
A shielding swarm of ice particles with infused ‘smart dust’ is attractive on a number of levels, not the least being that we can think of no physical laws such a swarm would violate, in sharp contrast to issues like faster than light travel or even the problems attendant on building a solid Dyson sphere (as opposed to a shell). The materials involved in a shielding swarm are those that would be available to any growing technology, and the construction and maintenance of such a swarm would be inexpensive to an advanced spacefaring culture.
…we conclude that successful mitigation of cosmic explosions risk is viable for sufficiently advanced technological societies, both future terrestrial and extraterrestrial. We suggest that building and maintaining shielding swarms of small particles/components is (relatively!) cheap and efficient way of achieving that goal and creating a durable planetary and interplanetary civilization. The technology required partially overlaps with that required for mitigation of asteroid/cometary impact risk, which could provide some clues for future technological desiderata and even convergence. Finally, this new type of macro- or astroengineering could not only enrich the spectrum of astroengineering possibilities, but also provide another opportunity for bold and innovative SETI programs to detect advanced technological civilizations elsewhere in the Galaxy.
Thus we have a possible new astroengineering signature to look for, and on that score, I think back to something Freeman Dyson said in a 1966 essay called “The Search for Extraterrestrial Technology.” Here he explains his view that if there are millions of places in the universe where light might develop, then we should not be thinking about average technological societies but those that are the most conspicuous. It is these we have the best chance to detect, and they will be the ones doing the biggest possible artificial activities.
Can we really rely on our extrapolations from our own technology to study this question? Here’s how Dyson stated the answer:
I assume that all engineering projects are carried out with technology which the human species of the year 1965 A.D. can understand. This assumption is totally unrealistic. I make it because I cannot sensibly discuss any technology which the human species does not yet understand. Obviously a technology which has existed for a million years will be likely to operate in ways which are quite different from our present ideas. However, I think this rule of allowing only technology which we already understand does not really weaken my argument. I am presenting an evidence proof for certain technological possibilities. I describe crude and clumsy methods which would be adequate for doing various things. If there are other more elegant methods for doing the same things, my conclusions will still be generally valid.
The paper is ?irkovi? and Vukoti?, “Long-term prospects: Mitigation of supernova and gamma-ray burst threat to intelligent beings,” accepted at Acta Astronautica. No preprint yet available but I’ll insert it when it appears. The Dyson paper I quote above is F.J. Dyson, “The search for extraterrestrial technology,” in: R.E. Marshak (Ed.) Perspectives in Modern Physics, Interscience Publishers, New York, 1966, pp. 641–655.
