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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.
Planets are common. Planets within the habitable zone look like they are common. So, is this evidence of the Great Filter - https://en.wikipedia.org/wiki/... ?
There is this huge assumption that alien civilizations will be emitting large amounts of waste heat. What happens if they are just more efficient than us?
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.
...as of thousands to millions of years ago, anyway? Speed of light, and all.
Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or
Incorrect conclusion.
The analysis was about civilizations that use energy on a galactic scale. It makes no conclusions about intelligent civilizations that use energy on the scale of human civilization. There could be trillions of human-scale civilizations out there; this analysis would not notice them.
advanced civilizations are far more efficient in their use of energy than is reasonable to assume.
Again, bad conclusion. We have not way to estimate what is "reasonable" to assume for a galactic-scale civilization. Kardashev defined a type-III civlilzation as one that used energy on the scale of galactic energy production, but gave no reasoning as to what a civilization would do that requires this much energy.
http://www.geoffreylandis.com
The firmament is peppered with huge concentrations of high-density plasma, supporting computation and communication far beyond the capacity of low-temperature, low-energy, solid-state matter. The byproducts of all that computation and communication look to us like thermal and optical noise because, being advanced, the minds running on them do so efficiently. Why leak information out into the vast, cold universe before you've taken full advantage of your substrate's Shannon capacity?
But, no, you're probably right. If there are other civilizations out there, why aren't we seeing the smoke from their cook-fires?
It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely the products of a deranged imagination.
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.
About the heat emissions... dunno what to say. An advanced civilization might be so thinned out, galactic-wise that it would emit an insignificant amount of heat. Or it could be a race which doesn't reproduce easily and lives for a long time, e.g. a couple million sentient beings per planet, who need very little in terms of energy. The possibilities are limitless.
Just wondering... how much heat does mankind generate? Can someone 1000 LY away detect our heat emissions?
...gis sdrawkcab (usually not responding to ACs; don't bother posting as AC)
Perhaps intelligent civilization will originate from Earth and spread across the Universe. Everything has a beginning.
You can't escape waste heat; it's part of entropy. Unless maybe you open a subspace portal or something like that, but obviously our understanding of physics doesn't allow for anything of that sort.
This is the problem with trying to understand hypothetical advanced civilizations; if any really exist, most likely they're figured out things in physics which we still have no clue about. We only started figuring out quantum mechanics about a century ago, and without that we wouldn't have semiconductors, including microchips and LEDs. We've barely even gotten off our own planet.
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.
It's kinda hard to have evidence of aliens if you never bother to leave your own planet, or send any probes beyond your own star system. Basically, such evidence would require the aliens to travel here to visit us. If there's any aliens out there in nuclear-powered generation ships or whatever, there's no way for us to see them until they're in orbit around our planet.
There's a whole galaxy out there we haven't explored, plus billions more galaxies beyond that. Just because we don't have reliable evidence of aliens visiting us here on Earth (aside from things like Roswell and cattle mutilations and claims of abductions) doesn't mean there aren't any out there anywhere; it's ridiculously arrogant and stupid to even think that. There could be aliens with a civilization similar to ours on one of the planets at our nearest neighbor, Alpha Centauri, and we wouldn't know it because we have no way of seeing them. Maybe they're technologically where we were in 1830 and haven't developed radio yet, or maybe they're 150 years ahead of us and have gone to spread-spectrum communication so their transmissions just look like noise to us and we missed all the detectable stuff.
If you consume that energy, it doesn't matter how you transport it; even if it's 100% efficient, you're going to consume it somewhere, doing something, and then it'll be emitted as waste heat. This is basic entropy in physics.
The only way around this is if you find some unknown-to-us branch of physics that doesn't require entropy (maybe you divert the waste heat to a parallel universe or hyperspace or something).
If we're looking at other galaxies, we're seeing what happened 100,000 years ago or more. Maybe the people in the Andromeda galaxy went from living in trees scratching themselves to ruling the entire galaxy in that time. Also, who says they have to be Type III? Neither Star Trek nor Star Wars are throwing around galactic levels of energy, but they're way ahead of us. Maybe there are aliens at that level, too distant for us to detect.
Slow down, cowboy! It has been 4 hours since you last posted. You must wait another few hours.
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
All this really says is that civilizations emitting IR were not found in Y regions of the galaxy at time X in history.
Since these regions are different 'light years' away in distance, what reaches us is not the current state of what's going on there.
An advanced planet 500 light years from Earth looking today for other advanced race would not find us since 500 years ago we were not creating IR signatures.
Likewise, if we found such a signature, the possibility exists that during the time the IR got here, that civilization ceased to exist.
At the very least, there's a major hurdle of unprecedented height to flying around the universe: FTL travel that breaks the laws of physics as we currently know them.
I think that even if a species had the social cohesiveness to launch and run a generation ship, the odds of getting anywhere before some random catastrophe strikes that eventually leads to the whole ship's demise would be astronomical. They might deplete their home planet's resources from building generation ships before they have any success with them.
"When information is power, privacy is freedom" - Jah-Wren Ryel
How do we even know the warm dust isn't the substrate for an advanced civilization?
Don't just stand there, get that other dog!
Another possibility is we are the only ones around.
Any research or theory that is validated by the assumption that we could have any idea about the capabilities, motivations and actions of such advanced civilisations is naive, because it does not accept how naive we are given our level of scientific knowledge and how far beyond our current understanding of the universe that such an intelligence would be. And I do mean intelligence, singular, because that is an inevitable precursor to a singularity and whatever follows. If an advanced civilisation's computational resources operate using the patterns in the interaction of seas of virtual particles there would be no easily detectable entropy change from the computation itself, only the I/O may touch the sphere of physics that we have knowledge of, and even this is not necessary as the computation manipulation of what we see as the known universe may be as subtle as simply influencing the probability of outcomes at a quantum scale. i.e. This study is the equivalent of a Victorian amateur scientist looking for grandfather clocks in the hope of proving that nuclear reactors exist on Mars.