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SETI@Home Adds New Search Method
Posted by
Soulskill
on Sun Jul 27, 2008 12:19 PM
from the look-for-interstellar-torrents dept.
from the look-for-interstellar-torrents dept.
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."
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Surprising (Score:5, Insightful)
Re:Surprising (Score:5, Funny)
Broadband wasn't common in 1999. Now they figure aliens must have upgraded too. ;)
Parent
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We got the idea that aliens will send a signal with a wide bandwidth over a short time, because we are doing that too.
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.
Parent
Re:Surprising (Score:5, Informative)
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Yes but (Score:4, Insightful)
Re:Yes but (Score:5, Insightful)
The cost in electricity for them to use my "unused" resources is not worth it for SETI which offers and most likely will never offer any tangible benefit to our society.
True, but who are you to say what others due with their free CPU cycles?
Personally, I like protein folding, but if other people want to look for alien life with their cycles then its their computer.
Parent
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"Do", not "due". And I got the right to say the first time we had brownouts in my area, and other people's energy wasting affected me. Not only do you waste an extra 40-100W per computer, but during summer, your ACs work harder too, cooling down that extra heat energy.
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Proverbs 27:1
Boast not thyself of tomorrow; for thou knowest not what a day may bring forth.
In this case foolish to assume SETI is an empty hope.
Re: (Score:2, Insightful)
T>True, but who are you to say what others due with their free CPU cycles?
CPU cycles aren't free these days (with good power management), they cost electricity and producing electricty usually leads to CO2 emissions and thus contributes to global warming.
Your pointless SETI computations are heating up my planet, so I can bloody well complain about it.
Now, finding a large prime number on the other hand, might earn me an entry in the Guinness Book of World Records...
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Re:Yes but (Score:5, Insightful)
Parent
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The proven existence of intelligent extraterrestrial life will have a profound effect on a lot of people's core religious beliefs. That alone will have a major effect on society and it might just turn a few people away from their outdated superstitious beliefs. I consider that a tangible benefit.
Sure, finding alien life will have a lot of impact. The thing is SETI won't do that, at least as far as basic physics and math is concerned.
But of course, it may end up replacing out outdated superstitious beliefs, and replacing them with more modern superstitious beliefs, such as trying to catch alien radio on our satelites. The parallels between doing this, and an old-school prayer to God are quite ironic.
Re:Yes but (Score:4, Insightful)
Parent
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Read the Rama series by Arthur C. Clarke and Gentry Lee, crappy fiction after the first one, but they examine things just like this.
And personally, extra-terrestrial life doesn't contradict my personal Christian beliefs.
Highly Debatable (Score:4, Insightful)
Yes, but is there any alien life? Certainly there's been no evidence of any, though you talk as though it certainly, and inevitably, exists. It sure sounds like you are the one making assumptions and promoting a faith based argument!
And as for this changing anyone's beliefs, that's highly debatable. Christian author CS Lewis wrote a trilogy in the late '40s that imagined intelligent life to be on both Mars and Venus. He was a noted apologist and theologian for the Christian faith, and he had no problem with considering the existence of extraterrestrials. (Note: The starting book of the trilogy was called Out of the Silent Planet).
Parent
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How do you pull bullshit from that?
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I don't fucking care & refuse to show any respect, or even read anything you've said after it.
This is why we need people to be more rational.
Re:Erm... (Score:4, Insightful)
His point was that people can be good without being religious. And of course people can be nasty and religious at the same time.
...go fuck yourself.
Your posts have done a lot to back up his claim.
Parent
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Re: (Score:3, Informative)
Isn't it the whole point of SETI@Home to use the normally unused cycles which you are already spending electricity and therefore money on?
The thing is that idle CPU time uses minimal electricity and generates minimal heat. The HLT command [wikipedia.org] means that you're using less energy. This is particularly noticeable in laptops. Run something that uses 100% CPU time (SETI@home/video conversion/etc) and see how long your battery lasts compared to simply having the machine sit at idle (turn off screen saver and power management software).
While it's not huge on a minute to minute basis, the cost of power adds up over the course of a year. I found this
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)
Why not? (Score:3, Insightful)
Re:we'll never find any signals (Score:5, Insightful)
SETI is not searching for accidental transmissions or leakage. SETI is only searching for deliberate beacons being sent by alien civilizations. SETI's techniques cannot detect random radio chatter and are not intended to.
Parent
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SETI is not trying to find civilizations like ours. It is trying to find significantly more advanced civilizations which are deliberately trying to contact civilizations like ours.
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Could you expand a little on that statement? I have two interpretations:
* Noisy-channel capacity theorems state that if information is being sent at less than channel capacity, error correcting codes can, in principle, ensure no errors on the part of the receiver, even in the presence of noise (in which case outside observers should have no problems decoding any messages);
* However, if information is being sent at over channel capacity, errors can grow without bound. If some ci
Re: (Score:2)
As the information in a radio signal approaches the Shannon limit, it becomes indistinguishable from noise to an outside observer.
Doesn't work that way. The Shannon limit restricts how much information you can pass in a noisy channel. SETI is looking for a very restricted question, is there a signal? That's just one bit of information. Listen long enough on the channel and that bit of information will come through, no matter how noisy the channel is.
About Time (Score:2)
Strange that they are only doing that now - haven't they seen Contact?
Re: (Score:2)
Strange that they are only doing that now - haven't they seen Contact?
What the hell are you talking about? In Contact the SETI is basically just a bunch of hippies who time-share radiotelescopes and look for signals by listening into headphones. Here we're talking about listening to bands hundreds of megahertz wide. Very different.
Use light, not radio waves (Score:2)
If I wanted to send a signal across the universe, I'd use light, not radio waves.
So, why is SETI still limiting itself to searching for signals in the radio spec
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Radio can be directional as well (microwave transmitters) - but all the worry about focussing is not really on the agenda - any alien who puts the effort into "focussing" a beam on us might as well just use some more obvious means of catching our attention - a bin
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Tight beams, eh? (Score:2)
The problem with a tight beam is that although you may get further, you only get one narrow beam that's unlikely to be crossed. A radiant energy is far more likely to be detected if it emanates in all directions.
So, combine your tight beam with continuous oscillation in all directions, and then you've got something.
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.
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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.
Ironic (Score:4, Insightful)
Re:Ironic (Score:4, Insightful)
The SETI line of thought is if another civilization is intelligent enough to understand the Hydrogen Line and the Microwave Window and that another civilization - us - would understand that as well and use it for radio astronomy, the frequency of Hydrogen (1420.40575 MHz) would be the most likely place we would be listening since the universe is mostly made up of it from what we can tell so far.
Parent
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.
That's progress, of a sort (Score:5, Informative)
Well, that's progress. I've criticized SETI@Home for looking for "carriers" signals with a large fixed-frequency component. They need to get beyond that. AM and FM signals have carriers (Analog TV is AM video with an FM audio subcarrier), and as a result, 80% of the signal energy is wasted. None of the more modern digital transmission systems have strong carriers.
The more efficient a transmission system, the more it looks like white noise if you don't know how to decode it. If there's some big repetitive component like a carrier, or the horizontal and vertical retrace intervals in analog TV, it's inefficient. The FCC wouldn't approve any new transmission system which wasted bandwidth like that, and the old ones that do are being phased out.
So SETI systems that look for carriers are looking for civilizations advanced enough to generate high-power RF signals, but not advanced enough to use more efficient digital modes. Our civilization went through that period in under a century. It's also fairly clear that nobody in our stellar neighborhood is continuously sending a strong RF carrier in our direction; that's been looked for.
Question: can the new SETI algorithm pick up an HDTV broadcast station?
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This may not work out as planned.
When I hear that "Thump, thump, thump" noise coming from a rice burner next to me at the stop light, I pretty much give the occupants the thumbs down on intelligence.
Re: (Score:2)
current topics include:
Nutritious Rice for the World
Help Conquer Cancer
AfricanClimate@Home
Discovering Dengue Drugs - Together
Human Proteome Folding - Phase 2 Project
FightAIDS@Home Project
Actually that is happening... (Score:2)
...In Soviet Russia!