by James & Gregory Benford
Talk of interstellar beacons invariably heats up the discussion, and I was fascinated to read not only Bob Krekorian’s take on the concept, but the follow-up comments of James and Gregory Benford, whose work on beacons has been examined previously in these pages. See A Beacon-Oriented Strategy for SETI, as well as Jim Benford’s Regarding METI and SETI Motives and Jon Lomberg’s Interstellar Beacons: A Silence in Heaven? for our treatment of this topic. Meanwhile, what about putting some constraints on how an interstellar beacon would operate? Here are the Benford brothers with a look at one way to proceed.
Bob Krekorian’s ideas invite comments. He takes a simple model which has the virtues of minimizing Doppler shifts in SETI beacons: an outward-facing array in an AU scale orbit around a star, fed by solar panels and radiating outward. The concept isn’t fleshed out quantatively, so can’t be compared to approaches such as ours. And of course he couldn’t say much in a short editorial. Perhaps he should write a detailed version of his idea, so comparisons can be made.
But this concept has the limitations of previous attempts at describing beacons: insufficient constraints, leading to little quantifying. There’s no condition placed on a beacon to estimate its principal features. That’s why we introduced cost as a driving factor (for a detailed discussion of Earth-based beacon costs, see James Benford, Gregory Benford & Dominic Benford, Messaging with Cost Optimized Interstellar Beacons; for ET beacons, see Gregory Benford, James Benford & Dominic Benford, Searching for Cost Optimized Interstellar Beacons.
This quantifying approach is sobering, as it forces tradeoffs on otherwise open-ended speculations. But it also advances the subject, which many beacon speculations do not do. It’s simply much clearer to pick a major organizing principle – economics – than generalize from a special design (“stellar orbital beacon hypothesis”). As we’ve argued, minimizing cost and effort are far more general traits, and we’ve given reasons for expecting this among any evolved species. See our ‘Searching’ paper for references to others who previously pointed this out.
Other specific comments on Bob Krekorian’s ideas:
- 1. The concept seems to assume that the galactic plane and the orbital plane of the beacon solar system are the same. That’s highly unlikely. For example, the angle between the plane the Galaxy and the ecliptic of our solar system is slightly more than 60 degrees. Almost all star ecliptic planes will be angled with respect to the galactic plane, with few exceptions: this beacon concept could be used only if the angle were near zero, an unlikely event.
- 2. Bob gets the number of stars vs. distance a bit wrong. In the near region, the distribution is uniform, so star numbers increase as the cube of the beacon range, but only out to about 650 ly, where the disk thins to half the density of the plane. Total disk depth is~1300 light years, so the stellar distribution is not spherical beyond that distance. Then it goes over to a number increasing as the square of distance. Bob’s numbers don’t fit either of these domains. He could get better numbers from Project Cyclops, pg. 54.
- 3. Of course, narrower bandwidth beaming is more efficient. But, quite generally, high powers radiators are not narrow band. Broadband emitters (~MHz) eliminate the need for all Doppler adjustments anyway (See appendix in ‘Messaging’).
- 4. It’s an old idea that the acquisition signal will be in the form of a pointer that directs us to the primary communications channel.
- 5. Of course, placing it very close to the star will rule out laser beacons.
A comment on John Hunt, who appears to believe that beacons are cheap. Our analysis says otherwise. With the very lowest price technology we have today, beacons cost $200,000 per light year. A more likely cost is about ten times that. So a 1,000 ly beacon will be 200 M$-2 B$. Making many of these ‘200 billion beacons’ would cost at least 40 T$.
To quote ourselves:
“We assume that if they are social beings interested in a SETI conversation or passing on their heritage, they will know about tradeoffs between social goods, and thus, in whatever guise it takes, cost. But what if we suppose, for example, that aliens have very low cost labor, i.e., slaves or automata? With a finite number of automata, you can use them to do a finite number of tasks. And so you pick and choose by assigning value to the tasks, balancing the equivalent value of the labor used to prosecute those tasks. So choices are still made on the basis of available labor. The only case where labor has no value is where labor has no limit. That might be if aliens may live forever or have limitless armies of self-replicating automata, but such labor costs something, because resources, materials and energy, are not free.
“Our point is that all SETI search strategies must assume something about the Beacon builder, and that cost may drive some alien attempts at interstellar communication.”
I think that I have to correct what I wrote because it leaves the impression that I think that no one would use nukes at all cost.
I don’t think that. I think that only no sane person would carry out a nuclear first strike. That leaves unfortunately a lot of opportunities for a nuclear war. power hungry madmen are a legion. Someone could be so pushed in the corner by some other means that he has no choice but to use nuclear weapons or be wiped out. etc.
But I can not imagine that a message from extraterrestrials could trigger a nuclear war out of blue. At worst, it could perhaps accelerate a crisis that would end up in a world war anyway. But even that is unlikely.
In the present situation, there is just no possibility, unless the message is deliberately sent for that purpose ( imagine genocidal aliens transmitting a blueprint of antimatter weapon that can be manufactured using common household chemicals, or something similarly far fetched )
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In the present situation, there is just no possibility, unless the message is deliberately sent for that purpose ( imagine genocidal aliens transmitting a blueprint of antimatter weapon that can be manufactured using common household chemicals, or something similarly far fetched )
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The aliens need not be genocidal. They could be friendly and just want to chat. And so, planning ahead, they include blueprints for a communication device in the message their beacon is sending. But how can a primitive species launch a multi-million ton device into orbit – why by the use of an orion type ship. And just to make sure we can build such a ship and can access all the materials needed for it they include the details for a device that can extract minerals, including uranium for the bombs, from sea water. And suddenly even small groups can now obtain as much uranium as they want.
Just as a far fetched example of how an innocent seeming message could lead to disaster for us. When two cultures meet, one of them doesn’t need to be hostile in order to do damage to the second. Alien civilizations might be aware that an innocent seeming message could have an unforeseen impact and so create beacons that only a civilization that has already expanded into space can detect. It would not be that long a wait – 100 years or so. Alien civilizations that have expanded into space, and are looking for others, would be able to find them regardless of beacons so a beacon then, saying hi, wouldn’t be likely to do damage. A beacon in such a situation would just be an invitation for communication.
Hope I don’t sound too hostile. I just get so frustrated knowing that we have the technology now to get into space and we would rather waste our resources on killing each other. It’s a topic that makes me mad. Money for killing, but not for exploring the cosmos. Insane.
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But I can not imagine that a message from extraterrestrials could trigger a nuclear war out of blue.
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I doubt it too. However we humans are complicated. No telling how it would affect us. It might draw us together and help eliminate some of the conflicts. It might create a driving force that finally gets us to start expanding into space. That is what I am hoping for. If such an alien civilization exists close by then we will probably find it soon, 50 years or so, so we had better hope we are able to handle the shock.
A reactor? For $1,000,000? I want one to heat my pool!
By the way, I am looking for volunteers to help me purify the plutonium from the spent fuel, to defray the cost. I hear it gets a good price in the Middle East. You’ll find me at the beach extracting uranium with my handy-dandy uranium extractor that I bought at home depot.
A reactor built that way would be unsuitable for anything but plutonium production. In fact it would consume energy to maintain forced cooling.
But the plutonium from it would be ‘weapon grade’. Not the reactor grade messy thing. So it would need only chemical separation that is easily achievable.
I see. In fact, when I googled the information, i stumbled at various posts at various nuclear physics related discussion boards that were obviously written by someone who looks for help in a clandestine nuclear weapon manufacture. Of course no one gave them what they were looking for. Physicists are not that stupid. But it was plainly obvious that the guys ( maybe it was the same guy because the writing style was very similar ) who posted questions like that were not extremely bright. Because they could just download a standard nuclear lattice code and try to do the computations on their own, as I did. As opposed to ask questions on discussion board in a manner that leave no doubt about what they really want.
Aliens With Lasers: SETI Bets On Nano-second Flashes From E.T.
Bruce Dorminey, Contributor
I’m a science journalist writing about over-the-horizon technology.
7/18/2012 @ 4:52AM |1,012 views
Dr. Ragbir Bhathal at the Australian Optical SETI Project, Rotary Observatory, at the University of Western Sydney (UWS) Campbelltown. Credit: Luke Fuda, Camden Advertiser (Fairfax Media)
Nearly four years ago, a tiny optical observatory in a remote Sydney suburb created a minor news flap after potentially detecting an intelligent laser signal from the direction of 47 Tucanae — a truly ancient globular cluster of some 35,000 stars in the southern constellation of Tucanae.
“We were doing the normal run on our 0.4 meter (16 in.) Telescope in December 2008 and found this spike on our computer screen,” said astrophysicist Ragbir Bhathal, Director of the Australian Optical SETI Project at the University of Western Sydney Campbelltown. “It was quite exciting to see this very sharp signal and I wrote on the print-out “Is it E.T.?”
But alas, No. Although Bhathal said there was no fault with the instruments; six months of trying to relocate the signal turned up nothing. “We have now dismissed it as spurious,” said Bhathal, who notes that instead of an intelligent signal from E.T., the spike was most likely caused by wayward cosmic rays.
Full article here:
http://www.forbes.com/sites/brucedorminey/2012/07/18/aliens-with-lasers-seti-bets-on-nano-second-flashes-from-e-t/?ss=innovation-science