No Intelligent Aliens Detected In Gliese 581 239
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."
Re:Correction: no signals detected (Score:5, Insightful)
That's not quite true. Some of our signals are spread spectrum, but the vast majority of licensed bands are still the age old single peak and often at insane output powers. These are very easy to distinguish from background noise, and as often is the case you could simply apply a 25kHz bandwidth and pick one of a few common coding methods and listen right in. The actual use of encryption for radio communication is rare when you're looking at the entire spectrum used over a planet. Hell if you exclude WiFi and satellite TV it's incredibly rare when you look at any major city too.
On that note satellites have pointed dishes because they are incredibly weak. They have to be, it's not like we have power stations up there powering them. When talking to a satellite we're trying to pick out a whisper from an asthmatic across a noisy room. We attempt to make our ears highly directional and filter out other conversations and he in turn cups his mouth to get his little voice that bit higher. That's not what these SETI projects are looking for. They are looking for aliens who have set up multi-Gigawatt transmitters all over their planet, just like we have. The equivalent of a rave happening somewhere else in an otherwise quiet rural town.
Also the directionality equation incorporates both the receive and transmit paths. You could have a perfect unit gain transmitter sending power out equally in every direction and still pick it up line of sight from anywhere you want with a theoretical infinite gain receive antenna pointed in the right direction, providing there's no louder signal source in your frequency of interest in the way. VLBI which is what they are using here provides an incredibly amount of gain at the receive side. Lots of really good signal analysis from multiple dishes result in us using a theoretical dish with a size and gain that could not realistically be constructed.
Some real geniuses came up with these designs and I'm willing to bet they know their antenna theory enough to think that it would be possible to detect a sufficiently advanced civilisation who take a similar evolutionary route that we take.
Re:proof? (Score:4, Insightful)
Re:Arrogant to presume no life. (Score:4, Insightful)
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.