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SETI Results By Scientific American
Paul Cobbaut writes "This http://www.sciam.com/2000/070 0issue/0700crawford.html is a link to an article on SA about Seti results so far. It discusses about why we found no ET yet, and provides more links." Very lucid and informative. Compare and contrast with a previous story.
See: Misconceptions Regarding SETI, Dyson Spheres and the Fermi Paradox
The bottom line is this -- nanotechnology enables the transition from pre-Kardashev-Type-I civilizations (us) to post-KT-II civilizations in decades. Such civilizations are resistant to almost all hazards on galactic scales and will thus be the dominant form of life in galaxies. If we are typical, it only takes a few hundred years to evolve from the discovery of the laws of physics to reach KT-II levels. KT-II civilizations survive for trillions of years. Unless the evolution of intelligent life is very, very difficult our galaxy should be dominiated by KT-II civilizations (Dyson shell supercomputers, a.k.a. Matrioshka Brains) with thought capacities in excess of a trillion trillion times the human mind.
Intentional communications generally occurs between entitites of approximately the same capacity. As we are at the sub-worm level in comparison to KT-II civilizations, they will not be directing communications at us. Non-intended leakage communications could be detected by SETI out to a few dozen light years, but we should be looking in the MHz frequences, not in the GHz frequencies. Therefore SETI@home is a waste of CPU cycles.
Interstellar travel is possible (the British Interplanetary Society Project Daedalus Study showed that). It is however pointless. The speed-of-light delays and communications costs for large volumes of data, mean you get little benefit from colonization. You do not want to become larger, you want to become smaller (or at least work very hard to minimize propagation delays)! The fact that KT-II civilizations can each build billions of lunar diameter telescopes makes rationalizations for interstellar travel difficult (why go "there" when you can "watch" there?). You also don't go very far, because "there", by the time you arrive, may not be there anymore (a closer civilization may have occupied the location). Arguments that we should colonize the galaxy in a few million years fail to understand that the rate of expansion is not limited by the speed-of-light but by the time it takes to dismantle planets, gas giants, brown dwarfs, etc. and turn them into something useful. It isn't the stars that are desirable to KT-II civilizations, it is planets with heavy metal abundances that "happen" to be on courses around the galaxy that these civilizations find attractive.
It is worth noting that the gravitational microlensing results, suggest that our galaxy is surrounded by ~200 billion "objects" of masses around 0.3-0.5 Msun. Astronomers are currently unable to provide an good explanation for what these might be. The best current guess is primordial black holes. (Of course most of the astronomers involved assume the universe is "dead".)
Comments by Verteiron, regarding the use of radio are absolutely correct. Given the capacities of KT-II civilizations, they are going to be able to build very large telescopes that can detect any other KT-II civilizations. If they want to communicate, they will do it using tightly focused lasers, probably in the blue or UV regions. This minimizes photon (energy) loss due to beam spreading and allows the highest data rates.
seti@home won't find alien life because it is just a distributed MP3 compression job on the Aricebo astronomers CD collection.
Bob.
One of the major reasons that ET will prove so elusive is the fact that we're not only looking at narrow slices of space, on narrow frequencies... but we're also looking for a signal that may encompass a very narrow slice of time for a civilization.
Putting aside the argument that intelligent life is not the "goal" of evolution (which is also a very good thing to remember), let's assume that an intelligent civilization DOES evolve out there. How long are they going to use radio for communication?
I don't claim to know tons about the area of the EM spectrum we're currently searching, but don't you think there will be better ways to communicate?
Analogy: Two tribes in two valleys separated by hills communicate via smoke signals. This is, to them, not only the best, but one of the only ways to communicate. Yet, all around them, even passing through them, are our radio waves, from our civilization, carrying speech and music, microwaves carrying our voices... Is it really so hard to adapt this analogy to our situation?
For all we know, there could be civilizations all around us, communicating; we just don't have the technology to detect the transmissions.
End of lesson. You may press the button.
Here's some thoughts I've had about SETI:
Something I've never seen is any information about how powerful the extraterrestrial signals have to be for us to hear them- to do that, we need to know how much gain the receiving antenna has, what the sensitivity of the receiver is, and the intensity of the background noise. From that information we can get an idea of what sort of transmitters (at what distance) we're looking for. For example, a big radio station in the US is about 100KW, with antennas that point the signal more or less to the horizon. We make it a point not to send too much energy up- the intensity pointing straight up at the sky is many dB down from the main lobe. Just how far away could the Aricibo antenna hear a station that had an effective 1KW (isotropic) pointed in their direction?
Of course the Aricibo antenna doesn't listen at the frequencies of FM radio, it listens to signals in the microwave region (for SETI work, from what I understand). At these frequencies, it is even easier to point the signal from an antenna. Unless someone is broadcasting to us intentionally, I have a feeling we're never going to hear them.
There has been much talk about how we've been broadcasting to the universe- but at stellar distances, all those signals are going to look like they're coming from the same point, albeit diverse in frequency. But everything at the same frequency gets added together- and if you add enough non-correlated signals together- guess what: it looks like noise! Can our signals compete with the EM noise put out by the Sun?
Another thing: as our technology improves, our signals look more and more like noise, and we use less effective power- consider any sort of spread spectrum- the energy has been spread out over a wide area to combat interference, lowering the peak power at any one frequency. At the same time we're making improvements with our receivers so that we don't need to transmit as much power. It all ends up as more efficient use of what we have (more bandwidth for the same power) I can't think of any expanding intelligence that couldn't see the utility of that- so as an intelligent race expands, the overall amount of unintended radiation may not go up proportinately.
On the other hand, I support SETI- I've got it running on 4 machines, and I've completed over 350 SETI@Home work units. If we don't look, we won't find anything until they land on the White House lawn. These are just some things I've been thinking about.
The next probe will probably carry a DVD instead. Now how do we explain to the aliens why these "lawyers" are coming to "sue" them simply because they really managed to decode our discs.
All opinions are my own - until criticized
- the existence of moon of sufficient size to help create tides and provide a just the right amount of long term stability to the earth to allow life to evolve. . . That is a rare event
- the extinction of the dinosaurs by an asteroid impact
- birth and procreation of mutated ape of sufficient intelligence to create civilization
- The existence of a very few brilliant individuals
- A long period of time without a life killing catastrophe of natural origin.
I think that if the probability of intelligent life arising naturally is nonzero (i.e. there is no divine intervention or the like required), then it must have happened many times throughout the universe; the universe is simply too unimaginably huge for it not to have. However, intelligent life in a galaxy a gigaparsec from us is not terribly interesting; if that's our closest neighbor, then we might as well be alone. The interesting question is whether there is intelligent life close enough that we might be able to interact with it someday, and on that question we are basically ignorant. We have no idea how typical our own planet and solar system really are. We have begun to see signs that planets, at least, are not all that uncommon, and this is progress, but we have no idea how likely the coincidences that allowed technological civilization to evolve really are. Any attempt to generalize from the one example we have to the galaxy as a whole is mere speculation. Not that there is anything wrong with speculation, mind you, but we should take care not to confuse our speculation with fact.Granted, but is this the only stable configuration? What about moons around gas giants? What about configurations that don't occur at all in our solar system?
Why is this necessary? Who is to say that the dinosaurs wouldn't have spawned an intelligent race on their own, had they survived. Or maybe they would have died off for other reasons; the late Cretaceous is not the only mass extinction in earth history, after all.
We have no data on how rare this really is, nor can we be sure that something resembling a primate is the only sort of life that can develop civilization.
This is a very distorted view of scientific and technological progress. Closer examination of history shows that when the time for an idea is right, there are usually many people working on it independently. We remember the one who got there first, and we forget the also-rans, but that doesn't mean they weren't there. If Newton had died of the plague, others would have picked up the torch. Maybe we would have had to wait another decade or two, but physics would have developed, just the same.
Sure, but how rare is that, really? With only our own planet's history to draw from, it's hard to say, exactly.
Since we are too ignorant to predict from theory what we might find out there, our only recourse is to look and see what we can turn up. SETI is a crude tool; there are too many ways for it to fail to detect something that really is out there. For the moment, however, it is the only tool we have. Someday we will have space-based interferometers that are capable of resolving nearby planets directly, and that will tell us a lot more about how typical or atypical our own planet really is. And after that, who knows? We may never find out whether or not we are alone, but if we don't look, then we'll definitely never know.
``Sure the game is rigged, but don't let that stop you. If you don't bet, then you can't win.'' --Robert A. Heinlein
-rpl