A couple of Canadian astronomers say that they have found periodic signals coming from roughly 200 stars out of millions in the Sloan Digital Sky Survey data. They say that they have eliminated earthly interference and a variety of other possible causes. Their paper is published in the
Publications of the Astronomical Society of the Pacific. And interestingly, most of the 200 or so signal-emitting stars are similar in spectral type to the Sun.
The SETI people expressed skepticism but say that they will follow it up.
The full-text of the paper is here:
http://iopscience.iop.org/article/10.108...ld.iop.org
I haven't read the entire paper, just the abstract summary and the conclusions. What's more, I probably lack the expertise to form an informed judgement of it if I did.
But my initial response is that these astronomers hypothesized a small set of possible explanations for their data, one of which was extraterrestrial intelligences. They proceeded to eliminate all of the hypotheses in their set except for ETI's, and concluded that it must be ETIs on that basis.
This raises one of the same philosophical issues that Leigha raised in the inference to the best explanation thread. If there are only a handful of competing hypotheses to explain some observations, and all the hypothesis but one seem to be eliminated, then the remaining one would be the best of that bunch. But that doesn't mean that it's the best in general, that it's the best of all possible explanations. The problem is that there may be all kinds of additional hypotheses that nobody has even considered that might better explain the observations.
So I'm inclined to think that these astronomers are probably reaching when they conclude that the periodic signals come from ETIs. They should be saying that the cause of the periodic signals is currently unknown. They can't be sure that the set of hypotheses that they considered and rejected was an exhaustive set that included all possible explanations for the signals.
Which raises the question, how can SETI researchers ever be sure that they have excluded all possible alternative explanations and really are detecting ETI's?
But if the billionaire was murdered in his estate, and all your suspects are the butler, the maid, his wife, the gardner, and the chauffer, why posit an unknown perp before ruling these out first? It doesn't advance the case to resign ourselves to an unknown cause of a phenomena without ruling out the known causes first, right? So how DOES one rule out aliens? That's the question..
(Oct 25, 2016 06:46 PM)Magical Realist Wrote: [ -> ]It doesn't advance the case to resign ourselves to an unknown cause of a phenomena without ruling out the known causes first, right? So how DOES one rule out aliens? That's the question..
ETIs are not a "known cause", so we have as much criteria to rule them out as we have criteria to rule out pink unicorns.
(Oct 25, 2016 08:28 PM)Syne Wrote: [ -> ] (Oct 25, 2016 06:46 PM)Magical Realist Wrote: [ -> ]It doesn't advance the case to resign ourselves to an unknown cause of a phenomena without ruling out the known causes first, right? So how DOES one rule out aliens? That's the question..
ETIs are not a "known cause", so we have as much criteria to rule them out as we have criteria to rule out pink unicorns.
Ofcourse it's a known cause. Aliens causing the signal can be known. The cause is thus known, not unknown.
(Oct 25, 2016 08:34 PM)Magical Realist Wrote: [ -> ]Ofcourse it's a known cause. Aliens causing the signal can be known. The cause is thus known, not unknown.
That presumes aliens exist...which we have no solid evidence for.
(Oct 25, 2016 08:39 PM)Syne Wrote: [ -> ] (Oct 25, 2016 08:34 PM)Magical Realist Wrote: [ -> ]Ofcourse it's a known cause. Aliens causing the signal can be known. The cause is thus known, not unknown.
That presumes aliens exist...which we have no solid evidence for.
There is no reason not to think they exist. The evolution of life is a universal phenomenon given the right conditions..
(Oct 25, 2016 06:46 PM)Magical Realist Wrote: [ -> ]It doesn't advance the case to resign ourselves to an unknown cause of a phenomena without ruling out the known causes first, right?
The explanation is going to be unknown if we don't know the explanation. That's just true by definition and it's the condition that researchers start out in. The best they can do is to better characterize the data so as to put constraints on the hypotheses that might account for it, then start imagining and testing candidate hypotheses. It probably makes sense to start out with what seem to us to be the most likely explanations and then eliminate them one by one. If the easy possibilities are all eliminated, more speculative ones need to be tested.
Quote:So how DOES one rule out aliens? That's the question.
I wasn't suggesting that aliens be ruled out. I was suggesting that these researchers shouldn't jump to the conclusion that it
was aliens when they don't really know that.
It reminds me of the discovery of pulsars. These mysterious objects put out a very precise periodic signal and it was originally hypothesized was that they might be aliens. (They were originally called "LGM" signals, for "little green men".) It turned out that they were rapidly rotating neutron stars.
http://www-outreach.phy.cam.ac.uk/camphy...ars4_1.htm
If nobody had ever thought of neutron stars and that idea wasn't already in researchers' intellectual tool kits, the now-accepted explanation might have been a lot longer coming.
Quote:The explanation is going to be unknown if we don't know the explanation. That's just true by definition and it's the condition that researchers start out in.
You're saying the only legit way we can posit aliens as a cause of these emissions is to know how the aliens would generate it? I don't think that is necessary. We can safely conclude advanced aliens upon seeing a giant space ship descending from the sky without knowing anything about how the spaceship runs. We are iow positing the aliens themselves as causes of the phenomenon, which is logical given their technological advancement beyond anything we are familiar with.
(Oct 25, 2016 08:45 PM)Magical Realist Wrote: [ -> ] (Oct 25, 2016 08:39 PM)Syne Wrote: [ -> ] (Oct 25, 2016 08:34 PM)Magical Realist Wrote: [ -> ]Ofcourse it's a known cause. Aliens causing the signal can be known. The cause is thus known, not unknown.
That presumes aliens exist...which we have no solid evidence for.
There is no reason not to think they exist. The evolution of life is a universal phenomenon given the right conditions..
I've had a tendency in the past to favor the agnostic or suspended belief resonances of the
Rare Earth Hypothesis, as a balance to the unbridled optimism that uncharacteristically gushes forth from corners that are otherwise skeptical about so many other "in theory" products. I suppose the recent "
Premature Life" hypothesis could be coupled to that.
My sympathies therein are of a "why I wouldn't be surprised" by the absence of intelligent life elsewhere in the Milky Way rather than a negative conviction or denial of there being rational ET agents.
In addition, a potential monkey wrench thrown into the whole works is that the technological self-replicating AIs and robots originally created by a living species could be all that survives in the long run or travels to the stars (the Black Monolith territory of
2001, A Space Odyssey). Thus setting-up potential quibbles over what constitutes "intelligent life" or what qualifies as life.
Even if ETIs exist, the chances are vanishingly remote that we would ever make contact with one, considering the size and duration of the universe. The chances hugely dwarf the odds that humans lived with dinosaurs, because the geologic time scale is nothing in comparison to the cosmic time scale. To my knowledge, we don't even have evidence for any extraterrestrial life, much less intelligent life.
And the relative dearth of TIs make me highly skeptical.