Slashdot Mirror
No Intelligent Aliens Detected In Gliese 581
astroengine writes "Using an Australian very long baseline array (VLBA) of three radio antennae, the first very long baseline interferometry (VLBI) campaign has been carried out on a SETI target star: the famous Gliese 581 red dwarf. However, after 8 hours of observing the star — thought to play host to six exoplanets, two of which are in the star's 'habitable zone' — no alien signals were detected. This result isn't surprising, as the likelihood of us stumbling across intelligent aliens living in the Gliese 581 system transmitting radio is extremely slim, but it does validate VLBI as a very exciting means of using the vast amount of exoplanetary data (coming from missions such as the Kepler space telescope) for 'directed SETI' projects."
Erm... do you even know what SETI is ? Or the concept of a round-trip ?
1) If we had sent a signal, it would take 20 years to get there, and we could expect a reply in no less than 40 years. Twice your estimate.
2) That doesn't actually matter however since we didn't send a signal at all. All we did was listen for signals coming from there. In other words - we were hoping maybe they sent us a signal 20 years ago - or more likely just generally sent out a signal in case *anybody* answers, or even more likely that we could catch a listen-in on a signal that was never intended for outsiders to begin with. If an alien race has satelite television - then any of the beamed-up signals that don't quite hit the target keeps going through space - SETI is really about trying to pick up any that may have come our way.
The most likely result we could get from SETI would probably be accidental signals - on the basis that any aliens running a seti project is most likely to get such signals from us (we sent a lot of signals into space, none of it is actually intended for alien consumption).
A signal intending to be picked up by other species (as in Sagan's Contact) would be a bonus.
That is actually the biggest problem I have with SETI. We're just listening hoping somebody else is bothering to talk or we pick up some stray signal. Truth is, we may well end up in a situation where half a dozen intelligent species are doing the same. All listening to space, waiting for the other one to actually say something.
Unicode killed the ASCII-art *
The point is if they are in a similar place in their technology as us, we would be receiving their 20 year old signals and there aren't any which is the problem with looking for folks like us. An intelligent life form could speak in a language made of chemistry (the way are cells talk to one another), and we won't hear that. They could be more primitive then us and we won't see that or hear that. They could be tremendously more advanced than us, and using our own advancing technology as a guide, would be producing noise across the EM spectrum, and looking for a signal in any one place might be futile. They may communicate point to point in very short very high energy bursts. They may not want to be seen by primitive species. The list of possibilities is almost endless, and point to real issues about how more advanced species might function in the universe, and there may be species as more advance compared to us as we are to bacteria. A couple tens of millions of years might do that for a sentient species.
So I believe the universe and specifically this galaxy is teaming with life. I just think the factor in the Drake equation that's going to mess with us is the symbol representing the technological state of a society. We have perhaps 20-50 years to go before technological singularity. That means the window of accessibility for a species being easily reachable may be less than 200 years. Making the ability to find others like us exceeding difficult.
If they're not smarter, better, or more civilized than we are, why would we want to meet them? Dealing with all the idiots here is more than enough, I don't want to have to deal with alien idiots too.
make imaginary.friends COUNT=100 VISIBLE=false
Just because there are no detectable radio signals doesn't mean there is no life, it may just be pre-industrial. WWII pushed us into the modern era. Without that we may still be using megabytes or even kilobytes and leaded gas. Maybe there is a planet with a single race and less aggressive tendencies, they may develop in a different fashion, while being advanced they may not be pumping massive RF for long-enough for us to detect. Not every species is going to be or was as addicted to TV and Radio as we are.
Having no detectable radio emissions does not preclude possibility of a civilization. Our civilization's emissions are already mostly in spread-spectrum format, which is by design indistinguishable from noise unless you know the encryption key. The transmitters we do have usually do not radiate omnidirectionally; that would be wasteful. Antennas are designed to cover the intended audience and minimize leakage outside of it, which makes detecting their radiation unlikely at any appreciable distance.
Futhermore, natural inverse square weakening of the signal makes the signal fade into the background before leaving the solar system anyway. Our TV and radio transmitters are not going to be heard outside the solar system. It is no coincidence that our satellites communicate with highly directional dishes. Directed signals are the only ones that will make it to the next star, so what SETI is really looking for is aliens who are actively broadcasting toward Earth. I don't know why they would be doing such a dumb thing, but who knows, maybe they are a not-too-intelligent life.
This result isn't surprising [...] but it does validate VLBI as a very exciting means
I'm a little confused as how a negative result validates the excitement-quotient. Or how this could even be validated in a more meaningul sense -- there's no way of checking the data. Maybe it was a false negative and there's oodles of aliens there.
The biggest technical problem in radio SETI is RFI. A signal from the star in question would have a very specific Doppler shift between the VLBI antennas, different from the relative Doppler shifts from any terrestrial RFI, even spill-over from a satellite. You can still have a saturated receiver if the RFI is too strong, but that is less of problem (it's easy to detect), and VLBI really reduces the chance of a false positive to almost nil. You also don't need an actual signal to show that this technique works.
Yes, they would want to contact us much in the same way we'd be insanely curious if any other creature on this planet demonstrated creative story-telling.
I'm sorry to poop on your post but that Calvin and Hobbes cartoon that inspired your reply is over 20 years old.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
One could argue that the Arecibo message was designed for alien consumption.
Do you care about the security of your wireless mouse?
You have obviously never worked at a VLBI correlator. Trust me, if they found something, you would know.
That's why we have to look for them. Duh. Think these things through. :)
make imaginary.friends COUNT=100 VISIBLE=false
Actually we are broadcasting VERY little now, and most of what we are transmitting won't leave our own system. this is why if other life exists its gonna be hell to catch a signal as there is a very small window between finding out how to broadcast and switching to digital, if other life follows a similar pattern.
ACs don't waste your time replying, your posts are never seen by me.
Not that magnetohydrodynamic drive exhaust is undetectable but from my understanding, the only way we'd ever see a "signature" is if the engine were pointing directly at us. Given our size, constant movement, and the minuscule amount of ions actually released the probability of ever detecting anything is probably infinitely close to zero.
FTA :
From our results we place an upper limit of 7 MW Hz1 on the power output of any isotropic emitter located in the Gliese 581 system, within this frequency range.
.
That means they could detect a 7 megawatt carrier tone with very narrow bandwidth of 1 HZ (or a 70 MW signal spread over 10 HZ, etc.) BUT, that is isotropic power. If the ETI was using something like the DSN antennas, much less something like Arecibo, they might have a gain of 60 dB, which means we could detect a signal down in the 10 Watt range. This search has enough sensitivity that there are lots of broadcasters on Earth (weather radar and airport radars, for example), that could be detected by this survey, if there happened to be a clone of our civilization at Gliese 581.
2) That doesn't actually matter however since we didn't send a signal at all.
But we did!
Unlikely. The human race is violent to the point of constantly being on the brink of destroying ourselves. Any species that was even the slightest bit more violent than humans would certainly destroy itself before reaching off-planet spaceflight.
This is true. Nearly all of what we have ever broadcast has been trashed into junk RF by the time it passes through our own heliopause. Voyager 1 and 2 are helping us learn that it is a fantastic filter aggressively scrubbing and sterilizing radio. Perhaps only a few terrifically strong military radar signals or intentional interplanetary signals (i.e. the powerful Arecibo transmissions) might have made it through. Decades of TV and radio have not. For practical purposes, our Sol system is silent. We are not emitting potent enough repeating signals of the sort we ourselves are seeking.
It is logical to expect a similar result for other planetary systems where something like a heliopause exists. RF would be trashed and never make it into interplanetary space.
For even more discouragement, remember that most of life on Earth does not use radio. A planet teeming with life might yet have nobody emitting even weak signals. Radio derives from the human need to communicate, constantly. Especially while driving. It is entirely possible that another similarly advanced species might not have that need to talk talk talk and entertain at a distance.
Anyway, the universe is a very big place. It's a long way down the road to the pharmacy, but that's nothing compared to the universe. Most of it is empty. On average, we don't actually exist at all. Sigh.
Sig for hire.
Actually we are broadcasting VERY little now, and most of what we are transmitting won't leave our own system. this is why if other life exists its gonna be hell to catch a signal as there is a very small window between finding out how to broadcast and switching to digital, if other life follows a similar pattern.
"Radio Astronomy" by John Kraus has a section on this topic. Well obviously he predates the digital transition. Not all that surprisingly large scale planetary radar has the best range, but the strongest long term signal used to be the constant (hopefully stable freq) of AM radio transmission carriers. You can integrate the carrier over months I suppose if necessary, detectable long below the data level
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
Most life on this planet is bacteria and viruses. They don't use radio. Most of the remaining life is a higher order of some sort, but still does not use radio. You have to go very far up the tree of life to find the one little branch where we alone are the single species using radio.
To put it another way, in the 4.5 billion year history of Earth, every other form of life that has every existed or still exists hasn't had radio. None of them had it. We do, but only for the last 120 years or so and less than that for advanced forms of radio. Averaged out, not only has essentially no life form on Earth ever had radio, it has also essentially never happened. 1 species, 120 years, out of billions of species and billions of years.
It did. But by no means is this something that just happens in the course of life.
Sig for hire.
Hoookay. What happened, did I respond after reading the article and embarrass you or something?
So, seriously are you saying it's mod-abuse or can you point out what's wrong with what I said in *this* thread?
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
The difference is that digital (as we are doing it anyway) is a much cleaner signal. We can get the same coverage for way less radiated power.
Radio signals carry infinitely far, given enough time. Detecting them depends on the sensitivity of the detector. We now detect signals from stars that started out 13 billion years ago, intercepting a tiny spot of power stretched thin on the surface of an expanding sphere that's about as big as our entire universe. Gliese 581 radio signals are far more powerful than that given its proximity (20 light years), unless we're looking for a single cellphone.
And what you just said about "just outside Pluto's orbit"? That's really meaningless. What's so special about Pluto's orbit? Even Pluto isn't anywhere near any one point on it except for a few seconds ever century. It isn't even always the most distant planetary orbit from the Sun, to say nothing of from the Earth; and there's other orbiting matter far beyond it. There's nothing about that arbitrary boundary that means anything, except to Pluto.
You obviously don't have any idea what you're talking about. Why are you saying it in public? Are you a masochist?
--
make install -not war
And only an AC emphasis on the C, would make such a deal about a typographical error... I can't remember hearing many idiots discussing the Drake Equation which either mean your IQ is 300 and you're comparing the conversation with your own lofty intellect, or you're just an insecure twit who adjusts their petty sense of self worth by pointing out ridiculous trivialities like typographical errors. Kudos on you blazing wit, perhaps next time you'd show more than half.
More like an intergalactic version of "Should I call her, or wait for her to call me" ?
Unicode killed the ASCII-art *
You might want to reread that quote from Adams. He did not express any of the erroneous formulas that you stipulate. Here's the full quote in all its glory:
It is known that there is an infinite number of worlds, but that not every one is inhabited. Therefore, there must be a finite nuber of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so if every planet in the Universe has a populations of zero then the entire population of the Universe must also be zero, and any people you may actually meet from time to time are merely the products of a deranged imagination.
So what he's actually saying is this:
X = # of worlds;
Y = # of inhabited Worlds;
X = infinite;
Y = finite;
infinite number >>> finite number (infinity has a higher magnitude than any finite number)
It follows: X/Y = 0 - epsilon, where epsilon approaches 0 infinitely close.
Thus: Average density of life per world so close to zero, that it functionally IS zero (remember, just like: 0.99999... = 1)
Summary: Any life one sees must be the product of a deranged mind. You could even go so far as calling it imaginary.
Actual summary: Expressing humorous quotes in terms of maths is exactly what it takes to take the humour out of them.
Actually, the cosmic microwave background is not really the afterglow of a big bang. Rather, the aliens have found out the ideal encoding for long-range space communications, which happens to look like 2.7 Kelvin thermal radiation if you don't know how to decode it. :-)
The Tao of math: The numbers you can count are not the real numbers.
You ought to be able to see that from a long way off if it's pointed at you.
Yeah, but directly?
The problem with that, probability-wise is that space is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space, listen...
"People don't want to learn linux" hasn't been a valid excuse since '03.
I find it amazing that some people are 100% sure that God doesn't exist (despite the fact that people have experienced God) yet insist just as vehemently that sentient space beings do, despite the fact that nobody has ever had any indication whatever (yet! I'd be surprised if we found none, nowhere) that any life at all exists off this rock, let alone sentient life.
Me, I think there probably is life out there, perhaps even sentient life, but if we find no life in the solar system besides here on earth, we'll never find any. The distance between stars is just too far.
Free Martian Whores!