SoylentNews is people
SoylentNews
Anonymous Coward writes:
https://www.businessinsider.com/alien-civilizations-may-have-already-colonized-galaxy-study-2019-8
The Milky Way could be teeming with interstellar alien civilizations — we just don't know about it because they haven't paid us a visit in 10 million years.
A study published last month in The Astronomical Journal[$] posits that intelligent extraterrestrial life could be taking its time to explore the galaxy, harnessing star systems' movement to make star-hopping easier.
The work is a new response to a question known as the Fermi paradox, which asks why we haven't detected signs of extraterrestrial intelligence.
This discussion has been archived.
No new comments can be posted.
Fermi Paradox Paper: Aliens Could Take Their Time Settling the Galaxy
|
Log In/Create an Account
| Top
| 93 comments
| Search Discussion
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
If the thunder don't get you, then the lightning will.
(Score: 2) by Arik on Tuesday September 10 2019, @06:09AM (36 children)
The point iirc was that if we assume baselines as best we can based on current experience, there should be thousands, probably millions or billions, of other civilizations and some of those should have been at the right point in their development to emit signs for us to see now. If we assume a few million Earth's scattered around the universe we'd expect at least one of them at the correct offset in time and space for us to be receiving their early TV broadcasts.
But we don't. So something has to be wrong with the initial assumptions. Or we're overlooking a signal we're receiving; perhaps mistaking it for natural noise.
The idea that there's an advanced civilization deliberately hiding themselves from us doesn't really impact the original insight. Maybe there is. But there should still be many other less advanced civilizations and at least one of them should be something we can detect and decode, assuming what we see locally is typical.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by NotSanguine on Tuesday September 10 2019, @06:25AM
The authors of the paper draw some interesting conclusions (paper is paywalled, abstract only) about how it might be possible for multiple (many?) spacefaring civilizations to settle significant areas of the galaxy without ever visiting earth. Their hypothesis (IMHO) could include distances/angles of transmission/radio interference which would preclude us from detecting signals from them as well.
From the paper's abstract [iop.org]:
It's an interesting idea, but despite the reasoning (at least that in the abstract), we have nowhere near enough information (again IMHO) to confirm or refute the authors' hypothesis.
No, no, you're not thinking; you're just being logical. --Niels Bohr
(Score: 2, Informative) by Anonymous Coward on Tuesday September 10 2019, @07:02AM (22 children)
But what signs do you expect to see? Radio doesn't work due to slow (lightspeed) propagation, and other methods of communication (if they exist, like tachyons) are not available to us. If other methods do not exist, there might be no point in communicating, and likely no point in sending sublight ships to faraway stars.
Maybe an advanced civilization could manipulate pulsars to encode information, but why would they do that? We do not encode anything for ants, hoping that one day they become sentient and read the messages. An advanced civilization will do what is reasonable, and that is minding its own business. They could be enthusiasts just like us - a million years ago. But now they know all that they need to know. Chances are that they are even done in this Universe (especially if it does not support FTL and will collapse/expand soon) and moved into other universes, with different laws of physics. Asking those civilizations to keep an ambassador to Earth's trilobites available 24/7 might be a bit unreasonable. We are not that important.
(Score: 2) by Arik on Tuesday September 10 2019, @07:10AM (21 children)
Assume every intelligent species spends about 100 years communicating by radio, as we did.
Yes, later on, they might develop any number of alternatives that would be harder for us to notice and decode.
But if we're really a typical product of our star, there are so many other stars of that type. At so many different distances. It's virtually impossible not one of them happened to go through their radio century at the right time for us to be watching it now.
If laughter is the best medicine, who are the best doctors?
(Score: 4, Insightful) by c0lo on Tuesday September 10 2019, @07:18AM (15 children)
You serious?
Assume a variation of "intelligent enough to use RF for TV" of some millions of years - which is a short time even in species evolution terms.
Divide that in intervals of 100 years. What's the probability you detect one if you are looking to the sky for only 60 years?
I'd rather say it's virtually impossible to detect them.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Arik on Tuesday September 10 2019, @07:28AM (14 children)
If laughter is the best medicine, who are the best doctors?
(Score: 1, Interesting) by Anonymous Coward on Tuesday September 10 2019, @07:41AM (4 children)
stars like the sun live for 10^10 years.
let's say that there are 10^3 years (cummulated over the 10 billion, for different civilizations) when inefficient radio transmissions are emitted by the planets with life.
if all stars like the sun develop technological civilizations, that means there should be, on average, about 10^7 stars like the sun close enough to us to detect the radio transmissions (i.e. distance small enough for signals to survive the inverse square law).
that is unfortunately not the case.
also: what you can see with the unaided eye is most likely on the order of 5000 stars, in good conditions.
(Score: 2) by Arik on Tuesday September 10 2019, @07:55AM (3 children)
Forget about naked eye though. We have much better instruments.
An aside, but proof that the universe is not infinite (or isn't even approximately uniform.) If it were infinite (and uniform) the night sky would be much brighter. In fact it would be uniformly bright. No matter which angle you look you should see nothing but stars. Sure, some much further away than others, but there shouldn't be any dark spots at all.
I mean, it could still be infinite, but if it is it's nowhere near uniform.
If laughter is the best medicine, who are the best doctors?
(Score: 1, Interesting) by Anonymous Coward on Tuesday September 10 2019, @08:18AM (2 children)
The speed of light and expansion of the universe cut off any galaxies farther away than 47 billion light years. The complete universe may or may not be infinite (I think it most likely is), but the observable universe certainly isn't; not only is it not infinite, it could never be infinite, and we know just how big it is.
(Score: 2) by Arik on Tuesday September 10 2019, @08:29AM (1 child)
Doesn't that strike you as too convenient?
Exactly the sort of nonsense an advanced civilization would invent if they wanted to quarantine us.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @10:49AM
Wow. Self-centered much?
If you knew anything about anything, you would know that speed of light being a constant is very important. One thing it prevents is the entire universe from "happening" at the same time.
(Score: 5, Informative) by c0lo on Tuesday September 10 2019, @08:07AM (8 children)
---
** optical, but I'm to lazy to search for radiotelescope dishes
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @08:33AM (1 child)
at this point i'm pretty sure arik is trolling, but please be aware that there is at least me who finds your replies informative.
(Score: 2) by Arik on Tuesday September 10 2019, @09:14AM
If I understand the subject better than anyone within 100 miles, and I know damn well I don't understand it at all, what am I to do?
I'm not above posting something that's clearly wrong and inviting anyone that has the ability to shred me. But when I'm doing that I usually write it out that way explicitly.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by Arik on Tuesday September 10 2019, @09:11AM (4 children)
I'm not sure your numbers are right; to the contrary they seem hard to accept. I remember in the freaking 80s being told by grey-haired professors in the field that if any civilization like our own existed at the correct time/space distance to be detected we could pick it up. No, we weren't scanning every possible angle at once, we were scanning a fairly small portion intensively and the rest got much less coverage, but we could pick up the signals not just in this galaxy but in several neighboring ones. And we were expecting to pick up an alien sitcom any day now. And we've been steadily expanding our coverage, surely there aren't many angles left unmonitored today?
So I don't now. Either my understanding of the tech back then was dramatically wrong, or we haven't expanded our abilities at anything remotely like we expected, or some other shit, or maybe as I think currently we are at a point where we could probably detect and decode a few extraterrestrial nee extrasolar transmissions were our basic assumptions about the universe correct, yet we do not detect those signals.
Or I guess you could go full infowars and claim we've got the signals they just aren't released.
Whatever. I'm not claiming I know what's going on I'm just pointing out why I doubt anyone else knows either.
If laughter is the best medicine, who are the best doctors?
(Score: 4, Interesting) by Runaway1956 on Tuesday September 10 2019, @10:15AM (2 children)
I strongly suspect those gray haired old men were full of something other than science. c0lo's post about the relative power of random noise generated by Jupiter, and the earth's total radio transmissions pretty much covers the matter. That amounts to a Ham radio operator trying to pull in the faintest of signals from the other side of the world on skip, while his neighbor cranks up the filthiest, noisiest, least filtered and most poorly tuned generator in the world. The generator is unintentionally broadcasting 100 to 1000 times more energy across the radio spectrum, than that distant Ham operator has at his disposal.
Those who were born before the ubiquity of resistor spark plugs remember how hard it was to pull in nearby radio stations, let alone distant stations. https://www.ngk.com/learning-center/article/804/what-is-a-resistor-spark-plug [ngk.com] Yesterday's rural radio nerd could sometimes tell you who was driving past his home, just by listening to the static generated by the vehicle.
(Score: 2) by Rupert Pupnick on Tuesday September 10 2019, @05:06PM (1 child)
Hair dryers were the absolutely worst sources of RFI back in days of analog transmission through free space.
(Score: 1, Insightful) by Anonymous Coward on Wednesday September 11 2019, @03:34AM
Nope. Arc welder. Ask how my neighbor knows. ;)
(Score: 3, Insightful) by c0lo on Tuesday September 10 2019, @11:00AM
I would start here and determine the maximum distance at which we could detect something emitted with a reasonable power (keeping into account the entire Earth civilization radiated EM power is 0.1 GW).
The most modern radio-telescope [wikipedia.org] can search (alone) to a distance of 28 ly.
The thing get funny pretty quickly if you start taking into account things like the wavefront form - TV emission make sense to be emitted in a plane, the "vertical" lobe of an antenna would be just losses for TV. So, imagine a plane on strong emission tangent to a planet that's rotating. How long that plane will sweep an observation point at some light-years away? Will the blip be long enough to be considered "encoded TV signal" by the receiver? If you assume many such "emission planes" from many TV stations on that rotating planet, will the signal received at distance look like "encoded TV" or just noise? SETI [wikipedia.org]
Oops - 1 hour of continuous encoded transmission? Only if they deliberately maintain the direction of emission for that time. As they don't know we are here, it will be an almost literal stab in the dark [wikipedia.org].
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Muad'Dave on Wednesday September 11 2019, @12:44PM
Most of your analysis is spot-on, but I have to disagree with the way you used this factoid.
That's the power emitted by planet Earth itself, not Earth's inhabitants. Our radio signature is significantly stronger than 0.1 GW = 100MW - in fact, the Arecibo transmitter [wikipedia.org] alone outshines the Earth's RF emissions by 5 orders of magnitude on one frequency, at least in a very tight beam. Arecibo has "... four radar transmitters, with effective isotropic radiated powers of 20 TW (continuous) at 2380 MHz, 2.5 TW (pulse peak) at 430 MHz, 300 MW at 47 MHz, and 6 MW at 8 MHz."
If you discount that one as being too narrow, then add up all of the omnidirectional radar and shortwave transmitters. Many of the radar transmitters mentioned in table 2 of this doc [doc.gov] have EIRP's over a GW. Even though they're low duty cycle pulsed emissions, they'd still be detectable at very long distances.
Also, Earth's emissions are mostly in the HF band (as are Jupiter's). Seeing any emissions past UHF would indicate some other process, possibly intelligent, was at play.
(Score: 1, Insightful) by Anonymous Coward on Tuesday September 10 2019, @08:12AM (3 children)
Detecting radio emissions from a planet-bound civilization isn't actually very easy. We might, barely, be able to spot a copy of our own civilization if it were at Alpha Centauri. SETI is really just hoping to find a beacon aimed specifically at us, or a very bright omnidirectional one.
But there is a lot of stuff we could detect. A spacefaring civilization would eventually build a dyson swarm, and that would alter the emissions of the star in a way that would stand out. Tabby's star isn't aliens, but if it were, it wouldn't look that different.
The real question is why aliens haven't simply landed on Earth. Earth has been here for billions of years, and goofy pseudoscience shows on History channel notwithstanding, aliens have never been here. That's more than enough time for aliens to spread out over the entire galaxy. Which means they probably don't exist, at least in the Milky Way, probably not in the whole Local Group. If the Universe is infinite, there are aliens somewhere, but just too far away to detect. We might not have even spotted their galaxy yet. The paradox really isn't. Intelligent life is just very rare.
(Score: 2) by Arik on Tuesday September 10 2019, @08:55AM
Well no. There's no proof they've been here, but there's no proof they haven't either. A much more advanced civilization could probably infiltrate us freely, not the point.
Where are all the signals from civilizations that were at 20th century tech however many light years away they are from us, that we should see their broadcasts? Where their signals?
Why have we yet to pick up a single extraterrestrial broadcast? If intelligent life is something that normally develops on planets about this far from a yellow dwarf, and intelligent life normally spends about a century broadcasting RF before rearranging around different signalling conventions, then why have we yet to capture a single alien sitcom?
Either "intelligent" life meaning only something on par with us is much less common than we would otherwise think likely, or our own development path was abnormal, or or or. I can think of plenty of ors. You probably can too, I hope you can.
One of the most fundamental forms of intelligence is the ability to notice the bit that doesn't fit. But just noticing it is no guarantee you can explain it. And being able to explain it in a convincing and useful manner is still no guarantee you got it right.
We're still little more than rodents crawling on the surface of the third big rock out from a perfectly ordinary yellow dwarf star, on the edge of a perfectly normal spiral galaxy, somewhere. We should keep trying to understand, but we shouldn't feel too awful about recognizing that we clearly do not yet understand.
If laughter is the best medicine, who are the best doctors?
(Score: 3, Insightful) by HiThere on Tuesday September 10 2019, @08:28PM
Sorry, but we don't have evidence sufficient to show that aliens have never been here. In fact, it's hard to guess what evidence *could* show that. What's true is that we also have no indication that they *HAVE* ever been here.
OTOH, what would we expect to find. Suppose some alien trophy hunters landed during the time of the dinosaurs, and shot one of everything that was impressive to take their heads back. AND suppose that they were very sloppy campers, and didn't worry about garbage disposal. What evidence would you expect to be able to find, even if that area never ended up under a glacier?
I think that question just has to be filed under the "unresolved, no evidence either found or expected" file.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Wednesday September 11 2019, @05:15AM
Doesn't even need to be rare. Just very very far apart. A few light days is effectively infinite distance away, unless you go sci-fi.
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @09:07PM
(Score: 4, Informative) by c0lo on Tuesday September 10 2019, @07:13AM (6 children)
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly 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.”
Couple it with the inverse-square-law of radiation intensity with distance.
Couple it with the apparent magnitude of a planet emitting radio frequency at zillions of light years and how fast it goes in and out of focus if you don't know which direction you need to point and maintain your receiving dish.
Even it would be billions in Milky Way, the "solid angle density" of such planets would be infinitesimal. Scanning them all will require more time than the human species existed.
Put in your pipe and smoke the idea that we discovered Pluto less than 100 years ago. And heaps of other bodies in out minuscule solar system over the last 20 years.
Inhale deep at the idea that even today the discovery of near Earth asteroids [wikipedia.org] is
----
Speaking for myself, I wouldn't expect that.
Not only the detection has a spatial infinitesimal probability density (over the emission solid angle).
But if we consider the human civilization representative, it takes less than 100 years for the EM power of their TV shows to drop down to very low power levels.
First by efficient TV receivers that don't need that much power, second... why!... they invent cable TV and Netflix and Gen5 mobiles that share the EM spectrum for communications at low power levels.
So, if you don't overlap your observation in the time dimension with "early stage of TV development + light transit time" over 100 years, you gonna observe nothin' from them.
----
Bottom, the question of "Why haven't we detected ET by their early TV shows" boils down to "How immensely lucky do you think you are, punk?"
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Arik on Tuesday September 10 2019, @07:23AM (5 children)
Still we expect each and every one of them to have spent roughly a century in that phase.
How many G series stars are there in the sky? Some are young, some are old, but there are a staggering number of them.
Not one appears to be producing non-natural radio signals.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by c0lo on Tuesday September 10 2019, @08:10AM (2 children)
You're again making the implicit assumption that the humanity capacity to observe the sky is unbounded.
You may want to check that assumption and adjust your probability numbers.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Arik on Tuesday September 10 2019, @08:26AM (1 child)
If laughter is the best medicine, who are the best doctors?
(Score: 2) by c0lo on Tuesday September 10 2019, @08:46AM
Wrong track again. Verify your 'capabilities of detection' assumptions some more.
(not gonna involve myself in this argumentation anymore until you do your homework)
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @11:20AM
You may want to check your signal to noise ratio. How is that WiFi at home working when you are 2000km away? Can't get the signal? WTF??? It's very close!! Not even on Mars! And Mars is also very close. If you wish to pick up alien transmissions, you better be able to use your WiFi from fucking Mars at crystal clear signal level without any fancy antennas either. Regular tablet/laptop on Mars and regular router in your house.
Get my point? And this is only scratching the surface about ONE problem, never mind dozens of others I can think of.
Ignorance breeds stupid comments.
Here you even answered your own question without realizing it. These are fucking STARS. 1e26W power output and yet you can't even see them because they are so dim. And then you expect to see something 1e20x weaker transmission that wasn't even sent in our way.....
(Score: 2) by HiThere on Tuesday September 10 2019, @08:31PM
You're neglecting the drop off in signal power with the square of the distance.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by Nuke on Tuesday September 10 2019, @08:55AM (3 children)
It has been pointed out that among the first powerful signals emitted from Earth were public radio broadcasts, and they will have reached quite a few stars by now. Prominent among those would have been broadcasts of Hitler's rally speeches. Perhaps he scared them off, which might not be a bad thing.
(Score: 2, Insightful) by Arik on Tuesday September 10 2019, @09:21AM (1 child)
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @09:14PM
Unless they speak German but not Russian or English. ;-)
Or, even if they received _a_ broadcast, what are they odds they translated it right.
(Score: 0) by Anonymous Coward on Wednesday September 11 2019, @03:35AM
They were sent out on long and medium wavelengths. These require immense antennas to receive at the nearest star, maybe comparable to a planet in size. Namely, the free space path loss at 1 MHz is 303 dB, and if we were sending 10 kW (+70 dBm), the sentients over there will need a 170 dB antenna to have -100 dBm at their receiver. We stopped using this band, and the ETs should be smart enough to do the same. Normal (for us) radio astronomy frequencies are in GHz, like SETI's 1420 MHz.
But that number is true only if they use the filter that is matching the spectrum of the signal. If not, the power drops further. Anyway, 170 dB gain, if the antenna can be constructed at all, will result in a very narrow beam. Now the poor ETs have to point this planet-sized antenna exactly to Earth! Do they do that? Well, we certainly don't, we have no orientable MW antennas, and besides the noise floor in this band is pretty bad, good luck pulling an unknown analog signal from tens if not hundreds of dB below.
The TV broadcasts did use a bit higher frequencies like 100-200 MHz, but that is still too low. Arecibo can receive 300 MHz - 10 GHz, but higher frequencies result in higher gain. As a reference, at 430 MHz the Arecibo dish provides 61 dBi gain. If we point two Arecibo dishes, one on Earth and one near Proxima Centauri, toward each other, and transmit 100 kW (+80 dBm), the receiver will get -150 dBm - a signal that could be detected, especially if digitally modulated (adds processing gain.)
There remains one class of RF emission that we are still producing. Radars. They are powerful, have high gain antennas, and operate generally at UHF and above. But who knows how their antennas are oriented, and how often they are used. Also, their frequencies are not linked to nature's constants, so an ET would have to search for a needle not in a haystack, but in a continent that is covered with a mile-thick layer of hay.
(Score: 3, Insightful) by Immerman on Tuesday September 10 2019, @01:35PM
Actually though, it's not nearly that odd - at present if Earth had a twin civilization orbitting the nearest star, it's doubtful that we'd be able to detect them - their radio emissions would be lost in the much louder radio noise from the star itself.
With current technology we'd really only be able to detect intentional interstellar radio communications directed directly at us, or that we happened to be almost perfectly in line with. (since tight-as-possible-beam communications would almost certainly be the rule due to power requirements) Or alternately, insanely high-power "beacons" designed specifically to draw the attention of young civilizations.