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.
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Fermi Paradox Paper: Aliens Could Take Their Time Settling the Galaxy
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(Score: 3, Insightful) by c0lo on Tuesday September 10 2019, @06:09AM (17 children)
Simplest explanation that satisfies the question: because we are stupid!
No paradox needs to be invoked.
(grin)
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 1, Informative) by Anonymous Coward on Tuesday September 10 2019, @08:12AM (10 children)
Exactly. We are really really stupid. We can't even see beyond our self-importance. If you understand this speech by Carl Sagal ... then you'll understand that Fermi Paradox is the opposite of humility.
https://www.youtube.com/watch?v=RESsY2y8G2s [youtube.com]
(Score: 2) by c0lo on Tuesday September 10 2019, @08:42AM (7 children)
I sometimes wonder if he was seriously believing it or he just threw it on the table as a 'a wild goose chase, left as homework for mediocre students to sweat until they learn how to think'.
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 1, Insightful) by Anonymous Coward on Tuesday September 10 2019, @10:46AM (6 children)
Not sure who your talking about "him" but I'm assuming to me? I'm not sure what Carl Sagan would think about. Anyway, Fermi Paradox is assumptions on assumptions, like this guy,
https://www.theguardian.com/lifeandstyle/2019/sep/09/all-you-need-is-maths-the-man-using-equations-to-find-love [theguardian.com]
and then you may notice, that communication is TWO way street. Fermi Paradox *assumes* that somehow *we* will see aliens and they will magically notice us too because we managed to move electrons and produce our own "invisible ether waves". But how is it any different than assuming aliens should notice or care about our smoke signals that preceded radio waves? It's as humble as stating "we know all physics and rest is just refinement".
Fermi Paradox was created by one arrogant ant on some hill somewhere!
(Score: 2) by c0lo on Tuesday September 10 2019, @11:06AM (1 child)
Sorry for being ambiguous, I was talking about Fermi, wondering if he was serious with his paradox or just teasing.
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Bot on Tuesday September 10 2019, @01:54PM
This seems a good context to remind us of
The Fermi paradox paradox:
"I just made the atomic bomb. Why don't aliens speak to us?"
Account abandoned.
(Score: 3, Insightful) by takyon on Tuesday September 10 2019, @11:18AM (3 children)
Two way communication is not needed for you to find out that an alien civilization exists. You could look for megastructures. You could look for exoplanets with biospheres, then focus on those planets to find further evidence of intelligent life.
Even finding evidence of a now-extinct civilization would be more satisfying than knowing nothing.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 3, Interesting) by Immerman on Tuesday September 10 2019, @01:29PM (2 children)
And at present we've detected one just-maybe megastructure (or unusual cloud of large debris), have detected a (large) handful of nearby planets whose orbital planes happen to be very near to our line of sight, and have the technology to get a very rough glimpse at the atmospheres of some of the very closest of those.
There's not really much reason to expect us to detect life that way. Not any time soon anyway, not unless the galaxy is absolutely teeming with it.
The usual presumption with the Fermi Paradox is that the aliens are communicating across interstellar distances, and we know all the physics necessary to detect those signals. Or alternately, that at least one species is in the process of colonizing the galaxy, and likely has been for millions if not billions of years - in which case it's odd that they're not already here in person.
(Score: 4, Interesting) by takyon on Tuesday September 10 2019, @03:05PM (1 child)
We went from a handful of known exoplanets to thousands in a short amount of time, but we are still in the dark ages of exoplanet detection, spectroscopy, and direct imaging. We will get better at it. We could use many gigantic space telescopes to get better results.
Megastructures are fun to look for, not necessarily the way we will confirm life. I brought them up because you don't need to find evidence of radio communications, just an optical detection. Maybe a dead civilization transmitting no signals could leave behind detectable megastructures.
There ought to be a larger number of exoplanets with biospheres than ones with intelligent life forms. So we need to detect smaller exoplanets, more of them, especially ones further away. We can look at atmospheric composition, or even directly image continents, vegetation, etc. on the surface. We might need telescopes with kilometer+ apertures and huge light collecting capability, along with starshades. A gravitational lens telescope [airspacemag.com] could also work (see Mars image and caption) but it will be hard to exploit that effect the way we want to at 550+ AU away. The "terrascope" [soylentnews.org] looks more promising in the short term.
Anyway, if you can find an exoplanet that has evidence of microbial or plant life, you have a good candidate for intense follow-up studies to look for signs of civilization. But even if we don't find intelligent life this way, we can work on the easier problem of finding biospheres (less terms in the Drake equation). These planets could become targets for our own interstellar expansion.
http://curious.astro.cornell.edu/people-and-astronomy/131-observational-astronomy/seti-and-extraterrestrial-life/seti/796-why-does-the-seti-project-search-for-radio-signals-intermediate [cornell.edu]
I think it's dubious that we can detect any interesting radio signals. Interference and noise would make a broadcast from Alpha Centauri hard to detect, much less anywhere further. And we can rule out the idea of detecting powerful, highly directional signals since that requires luck and good timing.
So the galaxy could be filled with alien AM, FM, etc. radio broadcasts and we would not know about it. It could be much easier to find a planet with vegetation on it and just continually improve our optical resolution until we can resolve any skyscrapers, electric lighting, etc.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by Immerman on Tuesday September 10 2019, @03:32PM
Quite so. It may well be that life is far easier to detect across interstellar distances than civilizations, At least life that re-engineers planets the way it did here - would we recognize the environmental signature of methane-breathing life? But as I recall even an ideal future telescope using the sun as a gravitational lens would have trouble resolving individual building on an planet around the closest star, so we'll likely be limited to detecting seasonal changes, and large-scale flocking behavior and have to infer the rest. Easily good enough for two-way communication if they knew we were here, but otherwise difficult to conclusively identify a technological civilization unless they were similarly big fans of artificial lighting at night.
At present though our technology is only good enough to barely dip our toes in that ocean.
(Score: 1) by khallow on Tuesday September 10 2019, @02:47PM
All which is completely irrelevant to the paradox. After all, if there were extraterrestrial aliens chatting in the bar and hanging out, no matter how stupid and self-important we were, the Fermi paradox would be resolved. Or if someone dug up a spaceship with galactic maps in the glove compartment, it still wouldn't matter.
TL;DR - emo is a waste of your time.
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @07:19PM
Is he related to Katey [snakkle.com]?
(Score: 3, Insightful) by DeathMonkey on Tuesday September 10 2019, @06:23PM (5 children)
Simplest explanation that satisfies the question: The universe is really fucking big.
(Score: 2) by HiThere on Tuesday September 10 2019, @08:16PM (4 children)
That doesn't really answer the question. If intelligent life is likely, and the universe is big, that just means that there should be more sources.
Much more likely is that they don't see any sense in wasting power in interstellar broadcasts and and physical travelers find, by the time they are in the neighborhood, that they aren't interested in planetary space. (If you and your family have lived on a ship for over 2 generations, you're not going to be anxious to leave it. Though in that case we might find residue of mining out around Pluto, if we looked carefully...and could figure out their mining techniques.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Insightful) by PartTimeZombie on Tuesday September 10 2019, @10:13PM (3 children)
We have no real idea what is going on in our own Oort cloud, which is part of our own back yard.
The last man left the Moon in 1972, and nobody has been even half that distance from Earth since.
If we had decided the space race had only just started in 1972, we might have found those space mines already.
(Score: 3, Interesting) by acid andy on Tuesday September 10 2019, @11:09PM (2 children)
This seems typical of humanity, doesn't it? Fleeting moments of enthusiasm, intense focus and brilliance, surrounded by decades of decline and self-destruction.
error count exceeds 100; stopping compilation
(Score: 2) by PartTimeZombie on Wednesday September 11 2019, @12:32AM (1 child)
I think we decided (as a species, pretty much) that because there is no obvious financial gain to be made from space it became not worth bothering with.
(Score: 2) by acid andy on Wednesday September 11 2019, @01:20PM
Yeah, that'll be it. And the pursuits that are built around financial gain very often aren't the ones that I'd consider moments of brilliance for humanity. I suppose you have charities and non-profit organizations doing great things and also billionaire pet projects like SpaceX but arguably nothing like that has been on quite the same scale as the space race.
error count exceeds 100; stopping compilation
(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/@ProfSteveKeen 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/@ProfSteveKeen 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.
“I have become friends with many school shooters” - Tampon Tim Walz
(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/@ProfSteveKeen 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/@ProfSteveKeen 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/@ProfSteveKeen 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/@ProfSteveKeen 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.
(Score: 1, Interesting) by Anonymous Coward on Tuesday September 10 2019, @07:30AM (21 children)
So, let's pick one factor from the Drake equasion: a species develloping high enough intelligence to get to space. Even here on Earth with millions of species (including bacteria and fungi), only one species managed to obtain the intelligence to get into space. All species originated from the same ancestor, yet one makes it into space and the others don't get the clue that they could achieve more than what they have been doing for ages.
Even with space being really big, we have no clue (a n=1) about how big the chances are that a species develops sufficient intelligence to travel among the stars. Maybe we just got really lucky as humans.
(Score: 1, Touché) by Anonymous Coward on Tuesday September 10 2019, @07:58AM (12 children)
Careful about that "lucky" part.. We are not traveling anywhere remotely near to "among the stars". We can't even fathom how to travel to our nearest neighbor. We are like a retarded squirrel that saw a tiny pond and can't even figure out how to float on it, never mind getting across an ocean. And the actual travelers are using planes or even something more advanced while we can't even think of imaging how to make a raft.
Yet we, the retarded squirrel, think we are intelligent and we wonder why other intelligent life didn't make contact.
(Score: 2, Interesting) by Anonymous Coward on Tuesday September 10 2019, @08:50AM (7 children)
My point is that there are no actual travelers. The retarded squirrel can look look up and see the plane, we aren't seeing anything that remotely hints on ET passing by. We are maybe just the best retarded squirrel that the universe has managed to generate (yet). We have here on earth some pretty intelligent species, that are able to use tools, sort things on shape or even are able to count. Even if we look at our closest relatives (apes) communicating with them is hard (mostly sign language), but try to explain, and let them perform, something simple as basic agriculture. I'm not sure if that would work. If a traveller would meet us and share their knowledge, our species would do their best to try to understand it... and will obtain at least some of that knowledge. Yet, we don't see the same happening on our planet where other species would aquire knowledge from us.
(Score: 2) by Immerman on Tuesday September 10 2019, @03:45PM (6 children)
>My point is that there are no actual travelers.
How do you know? Why would you assume we could see them? We're still discovering bushels of failed stars in our own galactic back yard that were too dim to see with previous telescopes, and their output almost certainly still dwarfs a spaceship's drive flame by many orders of magnitude. You really think we'd see the drive flame from a spaceship from hundreds (or tens of thousands) of light years away? And that's assuming they use rockets rather than something more exotic and less visible - we already have several theoretical alternatives, even if we have little idea how they might be implemented.
From what little we can see so far, we're the most interesting place for at least dozens, maybe hundreds of light years around. Unless aliens were specifically coming to see us they'd almost certainly never get close enough for us to spot them with current technology.
As for knowledge transfer not sure where you're going with that, but there are actually several documented cases of knowledge transfer from humans to other species - especially primates. Sign language being one of them, though it doesn't seem useful enough to have caught on in the wild.
(Score: 2) by HiThere on Tuesday September 10 2019, @08:36PM (5 children)
FWIW, I assume they use ion rockets, and that they don't use either high relative velocities or high thrust. And we couldn't see those even if fairly close.
OTOH, if you do assume a reasonably large fraction of C for their velocity, then I believe they WOULD be visible by dust particles crashing against them and being volatilized at extremely high temperature.
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(Score: 2) by Immerman on Wednesday September 11 2019, @01:27AM (4 children)
I think you're grossly overestimating how much interstellar dust there is. The Local Cloud - a gas cloud about 60 ly across that our solar system is currently passing through, has an average density of about 1 atom of hydrogen per 10 cubic centimeters, or 100,000 atoms per cubic meter. Assuming you're traveling atr roughly light speed, with no shielding to guide material harmlessly around your ship, then that means every 1m^2 of cross sectional area of your ship is going to hit ~10^21 atoms per year, or about 3.3 milligrams of material.
Even assuming total mass-energy conversion in the impact, that amounts to only 83MWh/year/m^2, or 9.5kW/m^2 of instantaneous radiation. A cylindrical ship 1km in diameter would be emitting only 7MW of radiation, and the overwhelming majority of that wouldn't be directed at us.
To put that in perspective, Pluto receives 0.9W/m^2 of solar radiation, with an albedo a bit over 0.5. Which means it's 1188km radius is glowing with about 2 million MW of reflected sunlight.
Pluto is also over about 6,000x closer than the nearest star, meaning it appears 36 million times brighter than it would if it were shining as brightly from the nearest star. We couldn't begin to see it there with current telescopes . And our 1km diameter relativistic ship passing that star would be another 600,000x dimmer than that.
(Score: 2) by HiThere on Wednesday September 11 2019, @03:16AM (3 children)
You've got a very low average dust, 1 atom per ?, but it's not evenly distributed. Some of it's in the form of grains of sand, some in the form of meteors, etc. And I doubt that we know enough to say how sparse the average dust is. (Well, unless you are really only counting dust particles small enough to fuzz light reception.) Some of it's even going to be in the form of wandering planets, and failed stars that are too small to count as a brown dwarf.
For that matter, at 0.01C it's going to be quite difficult to dodge a baseball sized chunk of rock by the time you detect it.
0.01C = 6.706e+6 mph
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(Score: 2) by Immerman on Wednesday September 11 2019, @03:12PM (2 children)
Sure, but traveling at near light speed the density will likely average out pretty well - you're sweeping through a LOT of volume every second, 235,000 cubic km for a 1km diameter ship. There may be more dim stretches with bright flashes, but my point is that even assuming massive ships and total mass-energy conversion on impact (almost certainly several orders of magnitude more energy release than in an actual impact), the total power output would be many, many orders of magnitude lower than we could detect across interstellar distances - even from a ship as close as the nearest star.
And I would assume that any species engaging in such travel would probably have worked out how to avoid hitting the softball-sized chunks, to say nothing of wandering planets and failed stars.
(Score: 2) by HiThere on Wednesday September 11 2019, @06:36PM (1 child)
As to not detecting it...well, OK. I think you'd get things like tracks in cloud chambers, but I could well be wrong.
As to avoiding them...this I find quite dubious. I don't even know of any hypothesis that says you could do that, bar things like hyperspace.
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(Score: 2) by Immerman on Thursday September 12 2019, @02:57PM
You might get some slight trace of particles reaching Earth as a result but they'd be totally lost in the massive onslaught of particles we're constantly being bombarded with from stellar-and galactic-scale particle accelerators scattered across the universe.
Avoiding debris is relatively easy - you have an active scanning and defense system vaporizing or deflecting bigger debris in you path, and an ionization+magnetic field shielding deflecting gas and dust around you. Takes a lot of energy, but if you can accelerate to those sorts of speeds in the first place that's probably not a problem. Avoiding wandering planets is even easier - you map their location long before you get anywhere close, and then don't chart a path through the space they're going to be in. If you can travel interstellar distances at relativistic speeds, then building gravitational-lens telescopes powerful to map your course ahead of time is a pocket-change endeavor.
(Score: 2) by takyon on Tuesday September 10 2019, @11:31AM (3 children)
We certainly can fathom how to travel to the nearest star.
We are probably decades out from having a stable multiplanetary presence in our own solar system. We could come up with a way to do interstellar travel, but it would be expensive and inefficient, and might require a generation ship or advanced robotics and frozen embryos. So maybe we should wait until the next century to make an attempt.
Decades to a century is a relatively short amount of time for humanity and in general. Short enough for us to avoid death by asteroid, cosmic ray burst, etc. that could be filters destroying intelligent or potentially intelligent life.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by HiThere on Tuesday September 10 2019, @08:39PM (2 children)
Sorry, but no. We've got parts of the answer of "how to travel to the nearest star", and if what you mean is "send a lump of metal" then we could do it now with enough effort. But our electronics wouldn't last under high velocity bombardment of particles, and we couldn't maintain a society that would man the listening devices.
We need lots of work on various areas, and one of the main ones is sociology.
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(Score: 3, Interesting) by takyon on Tuesday September 10 2019, @09:01PM (1 child)
We can use those nanoscale vacuum tubes or some other radiation-tolerant technology for the electronics. Not sure what you mean by listening devices. Some old school navigation?
If you don't want to do a generation ship, you could send a small group of people with anti-aging treatments to keep them alive for hundreds of years. That isn't available today so you'll have to wait some decades.
For particles bombarding the ship, either slow the ship down or add more shielding. Or both.
If you want to lower mass, send a ship without life support that can deploy robots and an artificial womb to create humans on site. Or find a way to completely freeze and unfreeze humans and keep them in a car trunk-like volume.
If there is a moderate chance of failure, send duplicate missions to each habitable exoplanet.
There will be much better options available in the future. My opinion is that there is no pressing need to do it this century.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by HiThere on Tuesday September 10 2019, @10:47PM
The "man the listening devises" means if nobody's listening when it sends signals back, we might as well not have sent it. Society back home isn't all that stable these days. We have trouble holding a "5-year plan" together. By the time it gets there someone will have lost the key frequencies, or defunded the telescope, or...well, any number of things from the last decade. E.g., at one point the 1960 Census original results were lost. AFAIK they still are. We had a copy on even parity 800 BPI track tape that became unreadable, and when we tried to replace it the census bureau had lost the originals. (OK, original is dubious use here because the actual originals were Hollerith cards, but I'd bet those were destroyed as so as the tapes were made and copied.)
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(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @09:16AM
Let's leave Trump voters out of it, M'kay?
(Score: 2) by Immerman on Tuesday September 10 2019, @01:42PM (6 children)
Well, there were at least a handful of other hominid species on Earth that might have eventually made it if they hadn't been displaced by our direct ancestors. And there's no telling what Earth's past might hide. There could easily have been a thriving race of spacefaring dinosaurs on Earth, and there's no real reason to expect us to see any evidence after so much time has passed (though who knows, we might find some very interesting artifacts preserved on the Moon).
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @02:33PM (5 children)
dinosaur civilization: you should expect to see boats buried in the sea floor near deltas (just like we're finding in Alexandria for instance).
sediment turns to rock with unnatural formation inside it, it will remain like this forever (just like bones got exposed at sea shore fossilized boats would get exposed).
not just that: at least some artifact of metal-wielding civilizations should survive (think bridge pillars collapsed on river bottom), even if oxidized, inside rocks.
my point is that a technological civilization will, in the blink of an eye, spread over the entire planet, and it will leave a continuous layer of junk over the entire planet. While you won't find it everywhere, there will be several locations that expose this particular fossil layer.
(Score: 2) by Immerman on Tuesday September 10 2019, @03:54PM (4 children)
Umm - the deltas didn't exist back then. Neither did the mountains, or most any other geological feature present today. The planet was entirely different then, and almost everything that was on the surface then is now either deep underground or long since eroded away. And most of the junk would have long since degraded - you find a dinosaur skeleton near some red-smeared rock stains, you're not going to know that those smears are all that's left of rusted-out industrial earth-moving equipment.
Alexandia was founded all of 2300 years ago. The dinosaurs went extinct 30,000x as long ago. Nothing "common sense" about archaeology is remotely relevant on those kinds of timescales.
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @07:39PM (3 children)
today's deltas will be rock formations in 60 million years.
as far as I know there are several important dinosaur sites that were preserved because they were river beds or deltas during the itme of the dinosaurs.
"the reddish smudge" is a reddish smudge; anything that could degrade a block of reinforced concrete that way would also degrade the dinosaur skeleton next to it.
(Score: 2) by HiThere on Tuesday September 10 2019, @08:42PM (2 children)
You are overly optimistic about the durability of concrete. The Romans made more durable concrete than our modern stuff, and I don't think their stuff would last that long.
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(Score: 2) by dry on Wednesday September 11 2019, @06:08AM
Bones are even less durable and we find evidence of them going back for 100's of millions of years. The same or similar processes such as mineral replacement could preserve concrete, metal and even plastic.
(Score: 0) by Anonymous Coward on Wednesday September 11 2019, @07:38AM
once you bury it in mud and you bury the mud under more mud, it will leave a lasting trace. just like bones and wood and feathers.
(Score: 0) by Anonymous Coward on Tuesday September 10 2019, @08:50AM (1 child)
I had a rug like this, for which I can thank my ex's dog. The trick is that while their civilisation was too small to see to the naked eye, you knew they were there due to the itchiness, bite marks and swelling; much like my ex.
(Score: 2) by acid andy on Tuesday September 10 2019, @11:37PM
Your ex was too small to see with the naked eye? Did you, like, keep her in a matchbox or something? Wouldn't you lose her down the back of the sofa?
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(Score: 1) by shrewdsheep on Tuesday September 10 2019, @09:53AM (1 child)
Every time Fermi comes about, the discussion gets repeated. I suggest, reality mimics Soylent: The settlers start, move around, lose their way and end up where they started. Over and over again. Any yet over again.
(Score: 2) by acid andy on Tuesday September 10 2019, @11:39PM
Yeah, this. Again.
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(Score: -1, Troll) by Anonymous Coward on Tuesday September 10 2019, @10:18AM
Fermi paradox can be sustained forever by just ignoring facts. If ignorance weakens, add more religion into society.
(Score: 2) by Gaaark on Tuesday September 10 2019, @11:26AM
There must be some kind of way out of here...
--- Please remind me if I haven't been civil to you: I'm channeling MDC. I have always been here. ---Gaaark 2.0 --
(Score: 1, Insightful) by Anonymous Coward on Tuesday September 10 2019, @12:27PM
Nice to see them crediting Kim Stanley Robinson for Aurora, but CiXin Liu probably deserves a mention for Dark Forest theory:
The galaxy is filled with civilizations but nobody reveals themselves for fear of getting annihilated by other civilizations.
https://bigthink.com/scotty-hendricks/the-dark-forest-theory-a-terrifying-explanation-of-why-we-havent-heard-from-aliens-yet [bigthink.com]
This sentiment was echoed by Stephen Hawking:
https://www.quora.com/What-is-Stephen-Hawkings-opinion-on-Fermis-Paradox [quora.com]
(Score: 2) by DannyB on Tuesday September 10 2019, @02:52PM
If aliens have advance intelligence, advanced technology, then they must also have advanced bureaucracy. Bureaucracy of the kind that even our computers such as they are, would be unable to cope.
Colonizing the galaxy is caught up in red tape.
Meanwhile, while you wait, listen to some vogon poetry.
The server will be down for replacement of vacuum tubes, belts, worn parts and lubrication of gears and bearings.
(Score: 2) by Barenflimski on Tuesday September 10 2019, @06:31PM (7 children)
I've always wondered why they would want to find us.
If they are traveling across vast distances of space, you would have to imagine they had figured out the key to unlimited energy.
If they have unlimited energy, one would think they could create any molecule they want. Resources seem unlikely.
Are they botanists? Maybe they want to find new plants for their planet? Maybe their ship broke down and they are light sailing to the nearest habitable planet?
For the most part, it would be dangerous for them to show up. The human race is far from stable. The first thing the powers that be would want is their technology to patent and sell it. We still have problems thinking its good to lift each other up. Most people want to stand on others shoulders.
We keep the peace by aiming nuclear weapons on dead man switches pointed at each other based on "Assured Destruction." If we can't trust each other, why would they, or us, believe we'd trust them more than the next human?
What does planet earth have to offer? Maybe people taste good? Maybe they like the taste of cat food?
It seems to me that the most likely scenario is played out in the movie 'District 9'.
(Score: 2) by takyon on Tuesday September 10 2019, @07:09PM (6 children)
There is an assumption here that the entire alien civilization would move in unison with a single purpose.
It seems more likely that there would be splinter groups off doing their own thing. Like Puritans migrating to North America. Or people colonizing Mars or other star systems.
So a space-faring civilization could end up fragmenting. Even if 99% decided to go die in VR sleep chambers, that leaves 1% that could be propagating, checking out new star systems, being scientist-tourists, etc. The civilization could last for billions of years by budding new groups faster than the old ones can be destroyed.
Unlimited energy/resources would make this even more likely. Lone individuals could obtain everything necessary for interstellar travel. Fusion/antimatter/whatever energy source, spaceship, anti-aging, robotic maintenance/assistance, entertainment, etc. Out of a species with millions, billions, or even trillions [nbcnews.com] of individuals, it would only take ONE to make contact with humans on Earth. Or visit and leave without us being capable of noticing.
This fragmentation makes you wonder again why they haven't conquered the entire galaxy. "They aren't from our galaxy or even close" is one possible answer, if not a satisfying one.
Anyway, if you have lone wolf individual aliens capable of visiting, why can't one of them be crazy enough to land on the White House lawn? Maybe because they haven't been around for the last thousand years instead of 10 million years. Maybe we had ancient alien visitors and we'll get some later. Or some are monitoring us in recent years, i.e. Zoo hypothesis.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by NotSanguine on Tuesday September 10 2019, @07:55PM (5 children)
Interestingly (and oddly, given that exactly no one -- well, except me -- bothered to put any focus on the paper TFA was based upon, and the hypotheses therein) the authors of the paper being reported are *attempting* to explain exactly that.
They posit that much of the galaxy may well be inhabited via colonization by spacefaring civilizations, but that the distributions of habitable star systems and the movement of star clusters may keep us from detecting them, and them from coming here.
From the paper's abstract:
It seems to me that this is an interesting hypothesis. What's more, it adds additional variables (e.g., the relative movements of stars/star clusters, and the potential distributions of habitable systems in the galaxy) to add more nuance to the discussion about why we haven't detected other civilizations.
No, no, you're not thinking; you're just being logical. --Niels Bohr
(Score: 2) by takyon on Tuesday September 10 2019, @08:21PM (1 child)
We currently have stars coming closer to us [wikipedia.org]. If we can barf humans at those stars, they will eventually be carried tens or hundreds of light years away from Earth, and they can spread to other nearby stars. Given enough time, the galaxy is ours. Or somebody's.
It is a big galaxy though, with a mass / number of stars that has been revised upwards [skyandtelescope.com]. Maybe there are pockets of pristine galaxy waiting to be conquered.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by NotSanguine on Tuesday September 10 2019, @08:58PM
Absolutely. And if it weren't for the risk of Kuru [wikipedia.org], I'd offer to barf such humans up myself.
As you're well aware, there are significant challenges to human (and alien) interstellar spaceflight, like constant boost drives, using ambient hydrogen for fuel, efficient life support systems, appropriate shielding at such high velocities, etc., etc., etc.
However, those are mostly (note I said "mostly") engineering issues rather than ones of basic science. As such, it seems likely that such voyages will be possible in the (not so near) future.
Constant acceleration at 1G (9.8m/s2) approaches the speed of light in less than a year. With initial acceleration at 1G, coasting and then decelerating at 1G, would take ~10-15 years to Alpha Centauri.
With future advances in living/collecting raw materials/construction/engineering in space, it would also be possible to build space/asteroid/moon based colonies where there are no habitable planets, thus extending the range of colonization each time such a colony (space-based or on a habitable planet) is established.
I'm just sorry I wasn't born in an era where this could be accomplished.
The paper referenced by TFA gives an interesting and nuanced counterpoint to the Fermi Paradox. Are the hypotheses in the paper correct? We don't have nearly enough data or the means to collect such data to confirm or refute them. As such, it's all just speculation (as is the Fermi Paradox, I'd add).
But it is quite interesting, IMHO.
No, no, you're not thinking; you're just being logical. --Niels Bohr
(Score: 2) by HiThere on Tuesday September 10 2019, @08:53PM (2 children)
That theory has benefits, but it seems to assume that civilizations will continue to be based around planets, which seems to me dubious. And it doesn't explain the lack of "von Neuman machines" doing the exploring. I think a better question is "If they had been here, how would we know?".
Most people seem to be fantasizing about FTL spaceships, but they seem dubious to me. And something, be it a machine or a society, that is adapted to traveling for centuries, at the minimum, in interstellar space isn't going to be attracted to moving to a planet. Paying a short visit, perhaps, but even that's dubious.
FWIW, if they ARE biologically similar to us to the point of having life based on amino acids, I would expect that exposure to Earth's atmosphere would be likely to set off anaphylactic shock.
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(Score: 2) by NotSanguine on Tuesday September 10 2019, @09:17PM
I'd say that it's not a theory (in the scientific sense), but a hypothesis which cannot currently be tested.
As for vonNeumann machines, how do you know they don't exist?
A fair point. However, the hypothesis in the paper (that our area of the galaxy has enough "deserts" around our local, perhaps 100 cubic light-years, make exploration/colonization of our part of the galaxy unattractive). could explain why we haven't seen evidence any extra-solar visitors.
As for FTL, the *very* theoretical Alcubierre drive aside, it is, as you say, a fantasy. But given cosmological time scales, colonization (whether based in a gravity well or in space habitats) of significant portions of the galaxy is certainly a possibility (see the latter part of my reply to Takyon [soylentnews.org] for some thoughts on how that could happen).
What's more, travel might not be on the order of centuries at all. Each new settlement in a new star system would expand the range of further colonization, on the order of ten or so light-years.
That's entirely possible. Perhaps even likely. But it isn't relevant (IMHO) to the idea of leapfrogging star systems to colonize significant portions of the galaxy.
No, no, you're not thinking; you're just being logical. --Niels Bohr
(Score: 2) by NotSanguine on Tuesday September 10 2019, @11:22PM
I was thinking about this statement and it occurs to me (I'd have added this to my earlier reply, but I didn't think about it then) that it's not so much that civilizations are or will continue to be based around planets, but rather around the stars they orbit. The star can provide the energy required and the debris around it (generally referred to as planets/asteroids/comets/etc.) can provide raw materials to build livable habitats.
If a planet is/could be habitable, it could be used as such. However, it's just (and perhaps more) likely that a spacefaring civilization would be more interested in stable stars with a minimal radiation fluctuations and planets with stable orbits within its habitable zone than "habitable planets."
Colonization doesn't necessarily mean farms and fisheries on a planet with a nitrogen-oxygen atmosphere. It could be just as effective with a (or, more likely tens of them) space-based habitat.
Given that interstellar travel will take decades even for relatively close stars, the technologies for space-based construction, life support and other basic living requirements would have been long addressed by any civilization with the capability to send living beings to other stars.
No, no, you're not thinking; you're just being logical. --Niels Bohr