SETI@Home Adds New Search Method 191
Adam Korbitz writes to point out that SETI@Home has added a new algorithm for use in evaluating signals from outer space. It's called "Astropulse," and they've made the scientific details available. Quoting:
"The original SETI@home is narrowband, meaning that it is listening for a particular radio frequency. That's like listening to an orchestra playing, and trying to hear when anyone plays the note "A sharp." Astropulse listens for short-time pulses. In the orchestra analogy, it's like listening for a quick drum beat, or a series of drumbeats. Since no one knows what extraterrestrial communications will 'sound like,' it seems like a good idea to search for several types of signals. In scientific terms, Astropulse is a sky survey that searches for microsecond transient radio pulses."
we'll never find any signals (Score:5, Interesting)
As the information in a radio signal approaches the Shannon limit, it becomes indistinguishable from noise to an outside observer. Any sufficiently advanced civilization will have the technology to maximize the information sent in a radio signal. Therefore we will not be able to detect radio signals from other civilizations (except for perhaps a 100-200 year period in their evolution where they use inefficient radio signals)
A terrible analogy (Score:5, Interesting)
As a musician and a recording engineer, I feel I must comment on the analogy used.
For someone with a trained ear picking out an A#, or any particular note, shouldn't be all that difficult, especially if that note is tonic, 3rd, 4th, 5th, or other similar high recognizable interval from the tonic. It would be trivially easy for someone with perfect pitch to pick out a particular note.
I suppose the analogy might hold if we compared the prior SETI searching signals to be like a man who is deaf in his right ear turning his left ear away the orchestra to try and determine if the 2nd piccolo is playing sharp on A#, and now, SETI is that same man, facing forward with a brand new hearing aid, merely trying to pick out staccato notes.
What are the chances? (Score:3, Interesting)
I wonder if similar detection rates have been calculated for SETI (e.g., assume ET having a transmitter of 1 MW, at what distance would you still detect anything? And how many life supporting planets are in that range? ) This will depend a lot on the parameters in your Drake's equations, but they should at least give some order of magnitudes. I remember reading some skeptic article several years ago, which claimed that even with optimistic estimates, the chance of detecting anything would be absolutely zero.
Until that time, I rather waste my computer cycles on the LIGO data (Einstein at home [uwm.edu]) or one of the various medical applications (e.g. Folding at home [stanford.edu]), which produce scientific results today.
Re:Use light, not radio waves (Score:2, Interesting)
Re:Yes but (Score:3, Interesting)
Re:Erm... (Score:2, Interesting)
You may have noticed that most species are wholly moral, they don't live hedonistic lives, and they love and care for their young and other members of their social group without need of intellection about imaginary Daddies.
How do you know this? I find it interesting that you can describe animals as having morals, and expressing love, but not religious beliefs. How do you know that animals don't believe in God?
Re:SETI is doomed (Score:2, Interesting)
Re:Surprising (Score:4, Interesting)
They chose 1420 megahertz for a good reason:
There is, however, a pronounced minimum in the radio-noise spectrum. Lying at the minimum or near it are several natural frequencies that should be discernible by all scientifically advanced societies. They are the resonant frequencies emitted by the more abundant molecules and free radicals m interstellar space. Perhaps the most obvious of these resonances is the frequency of 1,420 megahertz (millions of cycles per second). That frequency is emitted when the spinning electron in an atom of hydrogen spontaneously flips over so that its direction of spin is opposite to that of the proton comprising the nucleus of the hydrogen atom. The frequency of the spin-flip transition of hydrogen at 1,420 megahertz was first suggested as a channel for interstellar communication in 1959 by Philip Morrison and Giuseppe Cocconi. Such a channel may be too noisy for communication precisely because hydrogen, the most abundant interstellar gas, absorbs and emits radiation at that frequency. The number of other plausible and available communication channels is not large, so that determining the right one should not be too difficult.
Source:http://www.ufoevidence.org/documents/doc252.htm
More recently scientists have considered neutrino signals to be much more likely for alien communications since they can be sent across the universe with minimal signal degradation. The problem is that they are very hard to sense, and even harder to generate as a controllable signal.
SETI is an extreme misdirection (Score:3, Interesting)
SETI, as primarily currently pursued, is unlikely to find anything. I sum up my perspective, "We don't talk to nematodes and *they* don't talk to us." It is useful to consider the difference in intellectual capacity between humans and nematodes is far less than that between Matrioshka Brains and us.
Most advanced extraterrestrial civilizations are going to be far far ahead of us. At the point where they have constructed Matrioshka Brains. The intellectual capacity of an MBrain is roughly a trillion trillion times that of a human brain. They can simulate the history of entire humanities in seconds. We are simply not of interest to them.
There are 3 ways to detect MBrains.
1. Stellar occultations (similar to some of the exoplanet searches now being done).
2. Gravitational microlensing studies (also being done).
3. Large scale mid-to-far IR surveys looking for bright IR objects that do not appear to be visible (not being done because our far IR detectors are extremely poor and not particularly sensitive; and they must be operated from space so they are $$$).
The observant will note that none of these involve using computer cycles for the analysis of radio wave noise. The astronomer geeks will notice that long term backyard surveys searching for exoplanets using variations in stellar brightness might either capture candidate stars with exoplanets or perhaps an occasional gravitational microlensing event or maybe an MBrain traveling through the galaxy on its way to the nearest carbon white dwarf star (because they need more carbon for extreme nanotech) or a stellar gas nebula for a fueling pit stop. The extremely astute might notice that should sufficient numbers of these be discovered then there might be another explanation for all of the "dark matter" which doesn't result from the physics of the universe but from the natural activities of intelligent life. (Perhaps making the theoretical physicists extremely unhappy.)
It is also the case that to scan large fields of stars for variations in brightness and separating the normal variable stars from those which are "unusual" would not be a small use of ones spare computer time.
Congrats: You've missed the frigging point. (Score:1, Interesting)
SETI is not looking for 'leakage' transmission.
At this point in our own development it's unlikely that a civilization substantially more advanced than ours could detect our *own* leakage signals from interstellar distances. A strong obvious leakage signal is wasted energy.
Instead SETI is looking for intentional beacon signals, presumably ones designed to be easily detected and made by civilizations where energy is a few orders of magnitude less costly than it is for us.
Mostly SETI has looked for continuous signals on the microwave hydrogen line with the rationale that it would be a good frequency to put a beacon on because any one performing radio astronomy will be looking there. They've also been mostly looking for continuous carriers with the assumption that continuous carriers can be averaged for long spans of time and picked up out of the noise floor.
Now they are also looking for pulse like signals, the rationale being that with a given energy budget you can get higher above the noise floor using a pulsed signal... and that few natural phenomena have pulsed output.
So yes... what SETI has done in the past isn't optimal for the hopeless task of catching leakage current.
As to why we haven't found anything yet, we only need to consider ourselves: It would be completely reasonable to spend equal amounts of money on both SETI transmission (running our own beacons) as reception, yet we only do reception. Only for a few brief moments in the history of man have we produced beacon signals that we would have had any hope of picking up ourselves from another solar system. It may well be that the universe is chock full of intelligent life which are all listening but none speaking up.