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Advanced Civilizations Probably Don't Exist In Our Galactic Neighborhood
schwit1 writes: New observations of the best candidate galaxies now suggest that advanced civilizations are very rare or don't exist in the local universe. Researchers looked at several hundred nearby galaxies that emitted a high amount of mid-infrared radiation (abstract), which could possibly be produced as the waste heat from civilizations using energy on galactic scales.
They found: "The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust — for example, dust generated and heated by regions of massive star formation. As Professor Garrett explains: 'the original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilizations basically don't exist in the local Universe.'"
Obviously, the uncertainty of these results is quite high. Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or advanced civilizations are far more efficient in their use of energy than is reasonable to assume.
They found: "The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust — for example, dust generated and heated by regions of massive star formation. As Professor Garrett explains: 'the original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilizations basically don't exist in the local Universe.'"
Obviously, the uncertainty of these results is quite high. Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or advanced civilizations are far more efficient in their use of energy than is reasonable to assume.
Mmmno. The research doesn't indicate anything like that at all. They were looking for civilizations that harness energy and resources at galactic scales, ie. Kardashev III - level civilizations. Mankind haven't even reached Kardashev I yet. The submitter didn't understand what they were reading and jumped to conclusions.
Efficiency can only get you so far. You use enough energy, you will get waste heat as entropy, and entropy is inescapable. Of course, they might use hyperspatial redirection or subspace quantum oscillation phase modulation or something to make it look different to us or send it to another pocket dimension, but chances are, we'd have some indication of a Type III civilization.
What we should really be calling the summary out on is the fact that they equate a Type III civilization with an "advanced civilization". Yeah, it's advanced all right, but the bloody United Federation of Planets would only be something like a Type II. You have to control the energy output of an *entire galaxy* to be a Type III.
I'm no expert, but I remember reading that digital communication is virtually undetectable at galactic distances, because it fades way more quickly and becomes indistinguishable from background noise.
Nah, it's worse than that. Spectrum is finite, so the incentive over time is to use interesting encoding techniques to smear the data across the available spectrum. If you don't know the protocols, a given frequency mostly looks like noise in the time domain. And there are similar incentives to fill up the frequency domain. And there's incentive to use lower power, so that more transmitters can share the frequency, so those are all going to merge into a mess, too.
Basically, by design our radio output is tending towards noise which will be impossible to differentiate from a light year away.
You couldn't detect radio signals from a planet. The electric field of a radio signal drops off inversely with the distance that it's traveled, the intensity inversely with the square of the distance. The closest large galaxy is about 2.4 million light-years away. Compare that to the measly 100 light-years that our radio signals have traveled. In Andromeda, the intensity of our radio signal will have dropped off by a factor of about a billion -- 2.4 million years from now-- compared to the already weak signals that we sent 100 years ago. So we will not likely find a signal from another civilization like our own.
As far as detecting extremely advanced civilizations goes, it's silly to assume that they will output enough infrared heat to be detected on a galactic scale. Assuming they're able to overcome their population constraints (lack of resources, planets, living in space far from another star, etc), the heat that they generate on their own would still be negligible compared to even the dimmest brown dwarf stars that we can detect... unless you think that their population exceeds the mass of many thousands of stars. It's not downright impossible for a civilization to have spread throughout a galaxy -- it only takes about 250 million years to orbit your own galaxy -- but it's rather unlikely that we could see them from such distance.
Furthermore, it took Earth about 4 billion years to form (mind you, just the planet... the evolution was much quicker with a bit of luck). As far as we can tell, the universe has only been churning out planets for 13.6 billion years. So you might be hard pressed to look at galaxies much farther than 9 billion light-years, since we can only receive light from civilizations that have had the time to develop on formed planets with good chemicals.
I suspect that our best bet is looking at exoplanets within our own galaxy. As of now, we don't have a sun-sized telescope, so we'll have to stick with examining planetary atmospheres via transits (so absorption spectra of light coming from the star through the atmosphere). With some extreme amount of luck, we may be able to see the byproducts of an organic life-form within a planetary atmosphere, but there's no reason that it'd be life with advanced intelligence.
If you wanted to search for a signal from another civilization similar to our own, they'd probably have to be directing a strong signal towards us intentionally (and from within our own galaxy). I suggested to Geoff Marcy during a colloquium that we should look for signals within our own ecliptic, since if we've been discovered as a non-advanced life-form (remember we've only been technologically 'advanced' for less than 100 years), they would most likely have discovered our atmosphere via the transiting technique. You can actually detect transits in mass simply by observing the intensity of thousands of stars over a few decades. No need to zero in on a planet with a *giant* telescope. He seemed to think it was a decent idea, but I probably would have been better off by emailing someone at seti :P