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Fewer Than 10 ET Civilizations In Our Galaxy?
Al writes "The Fermi Paradox focuses on the existence of advanced civilizations elsewhere in the galaxy. If these civilizations are out there — and many analyses suggest the galaxy should be teeming with life — why haven't we seen them? Carlos Cotta and Álvaro Morales from the University of Malaga in Spain investigate another angle by considering the speed at which a sufficiently advanced civilization could colonize the galaxy. Various analyses suggest that using spacecraft that travel at a tenth of the speed of light, the colonization wavefront could take some 50 million years to sweep the galaxy. Others have calculated that it may be closer to 13 billion years, which may explain ET's absence. Cotta and Morales study how automated probes sent ahead of the colonization could explore the galaxy. If these probes left evidence of a visit that lasts for 100 million years, then there can be no more than about 10 civilizations out there."
Fewer Than 10 ET Civilizations In Our Galaxy?
All this is assuming that we would know immediately if there were a 50-100 million year old alien probe in our solar system's backyard. Stack that on top of all the non-empirical data based percentages that go into the Fermi paradox and ...
*puts on Twilight Zone music*
Human beings are the alien probe!
And man, we had better start compiling that report that's due when Quetzalcoatl/Jesus/Osiris/Thoth/Viracocha get back here. He's gonna be pissed when he sees that we just threw a huge party and trashed the place instead of assessing the resources!
My work here is dung.
We've known there to be at most 10 civilizations ever since Master of Orion. A typical scenario is more like 6 though.
I remember reading an interesting book called "The Science of Star Wars" that discussed the real life issues with the technology and situations in the original trilogy. This covered everything from the theoretical sciences behind the technologies like lightsabers, blasters, and lightspeed to the possibilities of existence of other life out there. I haven't read this book in a very long time and I don't have access to it at the moment, but I seem to remember it indicating that the odds of finding another planet with water, breathable air, and the exact distance from a sun necessary to help life flourish were so extremely low as to be laughable.
I remember thinking even then how short-sighted that was and how arrogant it seemed.
I realize these things are supposed to be scientific so they use only what they know to be fact, however, I think when dealing with complete unknowns such as the type of life out there or what their technology level may be at, you have to start thinking outside the box and be a bit more imaganitive.
Who is to say, for example, what form other life will take? Would we even recognize it as life if we were standing right next to it? What about their technology? Who is to say that they haven't gotten past the lightspeed issues with relativity and energy required? Perhaps they have stealth technologies... would we even be able to detect them? Just because we don't know how to do it now, and just because our current science says it probably isn't possible, doesn't mean it can't be done.
We pretty much know what rocks and ice look like. If the aliens aren't spectacularly good at masquerading as rock and ice, we'll recognize them.
I am curious as to what evidence these alien probes would leave if they don't land and stay on a planet. If they just fly around, collect data and phone it home we would never see them.
Even landing, unless they landed on Earth, our Moon or Mars, how would we see it? I'm not even certain our own probes can spot our own rovers on Mars. Lets say they did put a probe down on earth (like our mars rover) say recently, like 100,000,000 years ago; it could easily be hidden under a kilometer of dirt and rocks and never be found. Time, like space, is vast.
A good summary. Especially since they assume because we sent out a "identifier" once, that it is logical that all other civ's would continuously do that, just in case things change, and some youngsters show up. Instead of 1) send probes, get the info you want (or trash your orbit with satellites and crap so you can't lunch anything else) and give up, staying in your own solar system.
Not to mention we only see stuff at the speed of light, if they only send stuff at 1/10 the speed of light. Anyone over a thousand light years away hasn't even seen any signs of life in our galaxy yet, let alone had a chance to respond in a manner that we will then be able to see for a few thousand more light years.
It's always seemed to me that the major hole in the Fermi paradox is the assumption that technologically advanced alien civilizations would be emitting signals we would recognize.
I mean it's kinda hubristic to assume they want to talk to us. After all we may study chimps but we don't go out of our way to show up in the middle of nowhere to say hello. That leaves the question of why we don't detect communication leakage, e.g., radio signals they use for communication. However, not only is it not obvious that they would use radio to communicate, or that we could recognize such signals, but it's not even obvious they would bother to colonize the galaxy or communicate between planets.
For example suppose that sufficiently advanced civilizations transform themselves into some form of 'computational' life. Such a civilization couldn't care less about planents or minerals. What would matter to them is processing power per unit volume. It would therefore make sense for such civilizations to seek out the regions with the highest energy density that would allow them to access the most processing power. Rather than racing around the galaxy in starships and living at the same crawlingly slow pace we do such civilizations might exist entirely in the high energy regions in neutron stars or around black holes. So why would we expect to meet them. Hell, even if they care about meeting aliens too the aliens they care about are probably the ones who already inhabit similar regions.
Even if we think it's reasonable to assume aliens are sending messages all over the galaxy the more efficiently such messages are encoded the harder it will be for us to identify them. The closer such transmissions approach the Shannon limit for the communications channel the harder they would be to distinguish from random noise (and we don't know enough to rule out a natural source). Also the more effective use they made of their communications equipment the less stray signal that would wash the earth, even if it was encoded in radio instead of neutrinos or something weird (some papers have suggested neutrinos would be a better long range communication method).
The point is that even if we take for granted that there a fucktons of advanced alien civilizations around it just doesn't follow that we should be able to detect them.
If you liked this thought maybe you would find my blog nice too:
...and we haven't been back since. Beyond the question of how long it would take a motivated civilization to expand throughout the galaxy, there's the question of "would they bother?". We don't seem to be bothering.
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
-Calvin
Later incorporated into his novel Diaspora
http://www.geoffreylandis.com
To add to that:
If you took a completely alien language, encrypted it. Compressed the hell out of it, then applied 10,000 to a million years of technological advancement to the sending of it, would we even be able to notice it from background noise? Even if radio was still used to send it?
Ok, so we eventualy invent our own 0.5c space drives and go ahead and try to leave our solar system at 0.5c ...
We run through the Kuiper Belt where we collide with a tiny pebble that is lazily orbiting our solar system
The relative velocity of a bullet, fired from a low velocity pistol, when it hits something is generally between 300meters/second and 600meters/second. Now imagine a bullet with a relative velocity of 150,000,000meters/second. The problem isnt the space drives.... its that the "vacuum of space" has shit in it.
"His name was James Damore."
"Well, if you manage to colonize the whole galaxy, you probably don't have to worry about defending it from external threats for quite a while."
Okay, that's the funniest thing I've ever heard.
Q: What's the biggest threat humanity has ever faced?
A: Itself.
Creating thousands of splinter civilizations with no emotional investment in the species homeworld is a recipe for galactic war if I've ever heard one.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
You can't really think of colonizing a galaxy in the way you might think of colonizing a new continent. The distances alone would make sure whatever reaches the far end of the galaxy would be a completely different species than the originator of the "colonization". Barring faster-than-light travel or some kind of extreme (from our point of view) psychology and genetics, I see no way a civilization spanning an entire galaxy could exist. If we colonized Mars now, it wouldn't be very long before they started to go their own way. Hell, the Americas were lost to the parent countries in a few centuries, and that's on the same planet.
It just doesn't make much sense to take an expansionist view of space travel, unless maybe your species is very, very patient and stable. Any colonists you send far out, you will never have meaningful contact with again. At that point you might wonder what the point of "conquering" new systems is, in terms of nationalist-type expansionism.
Otherwise, societies are too self-absorbed to dedicate those sort of resources to a goal that will have ZERO benefit to them or their descendants.
It sucks for scientific types, for sure, but the best way to get the masses emotionally committed to space flight and space exploration is through religion. There's no more historically proven way that motivates people to build and explore for future purposes than the prospect of being able to worship your lord and impose his law as your religious customs see fit to do so. In 1620, it wasn't a bunch of scientists on board the Mayflower, it was a bunch of religious fanatics. In my site I'm going to go all out religion for space exploration as a national priority and argue in this order:
a) The Lord gave us the vast resources of the Heavens to use.
b) The Earth is a crowd and dank cesspool of sin.
c) You can establish a more Godly society on another planet.
d) You can re-create the American Experiment the way the founding fathers intended.
This is my sig.
bjourne points out: "They assume that alien civilizations would grow exponentially like humanity. To maintain exponential growth the civilization would inevitably have to colonize other planets, other solar systems and even other galaxies."
What they really assume is that the laws of physics apply broadly across the cosmos. Darwin and Malthus do the rest.
The real question is how hard it is to jump the gap from one world to the next. Science fiction authors assume this is not only possible but relatively easy, because otherwise they would have no story to write. Travel (of the few) within the solar system seems plausible. Travel (of the many) to neighboring stars is far beyond daunting.
Consider Malthusian growth: Our population today is 6.602 billion souls. The current growth rate is 1.167% per annum. (Numbers are a couple of years old - it doesn't change the result.) Do the math.
Today there were 210,000 more souls and 6000 tons more human flesh pressing inward on Mother Earth than yesterday. Tomorrow there will be 210,000 more. The day after - another 210,000. In six months that will be 211,000 per day - in a year, 212,000 per day, and so forth and so on. Less than a year from now there will be another 1.8 million tons of human flesh literally shouldering other species into extinction. That's not 1.8 million tons total - that's just the additional growth of skin and hair and sinew and good red meat locked up in your mama's Soylent Green recipe.
For space travel to matter in the solution of this problem, we have to build a fleet of ships capable of offloading 210,000 people - a new space fleet every day, year after year - forever. A space shuttle carries a crew of seven - so we need 30,000 space shuttles a day. (Of course, that only gets you to low Earth orbit.) Each year we would have to move at least that 1.8 million tons of human cold cuts - that's the equivalent of 18 Nimitz class aircraft carriers - to some other distant, unwelcoming world.
And then, of course, you've just shifted the horizon of the always looming catastrophe to a collection of planets rather than a single planet. Since this is a doubling issue, colonizing another planet - say, a terraformed Venus - just buys you an additional 60 years.
1 and 2 are both well known hypotheses. 3 is very unlikely, since we pick up radio emissions from natural sources all the time. 4 is very unlikely, but possible. 5 well known hypothesis 6 interesting! 7 very, very unlikely, given the natural sources we know about 8 what transmission medium does the telepathy use? Is it EM based? Is the range infinite so you don't have to use EM for long distance comm? 9 Yes, it's a bit silly. Radio isn't all that powerful. 10 Yeah, heard that one before once or twice, but not a well-known one. Good job! 11 well known hypothesis : all we can find at this point is beacons, and nobody is using them 12 well known hypothesis : optical works better, but of course is highly directional, and we're not on line of sight
Let alone evidence that would last a million years. A probe could have come through a thousand years ago, hung around taking pictures and measurements for a few years and moved on. We'd never know.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
It is possible that the probes lying at the bottom of the ocean were not designed to get wet because the host planet does not have water at all. Now these probes might be short circuited or something of that kind.
Expanding on this, what if they were looking for a planet like Mars or (harder to detect) Venus? Maybe the probe arived billions of years ago and saw three planets in adjacent orbits with water. Who's to say it would have picked the correct planet?
As for detection, a single object sitting under the dense atmosphere of Venus for 100 million years doesn't exactly pop out at us.
Write your representatives! Repeal the 2nd Law of Thermodynamics!
Your argument is silly. Buses pick you up from bus stops, not from your house. If you want to get on a bus you have to go to a bus stop. An intelligent civilization on a planet a thousand light years from Earth that has astronomers is going to look up and see a similar sky. Even if their eyes only work well in the infrared they can still build detectors (just like we do) that cover the entire EM spectrum. When they build their telescopes they will find the same things we have. Their radio telescopes will pick up synchrotron radiation, pulsars, AGNs, and the CMB. Their optical telescopes will see the same stars and they'll deduce similar if not the same cosmological and physical theories. An important thing they'll find are the hydrogen and hydroxyl lines in the microwave band. These lines are in the middle of a relatively quiet portion of the radio spectrum. These are both radio emission bus stops.
Any alien radio astronomers will be looking at the same frequencies that our radio astronomers do since they're both looking at all the same phenomena. If they decide to announce their presence to the rest of the galaxy their best bet will be to do so on a frequency other radio astronomers are likely to be looking at. You might catch a bus randomly passing by but your best bet is to wait at a bus stop since you can be reasonably sure a bus will eventually stop there. Interstellar messages don't have to be fully understood or translated to be important either. Simply receiving a coherent signal from another intelligent civilization would provide a wealth of information. For one it says "there's someone out there" and that signal is going to come from a specific place. Other types of telescopes can be trained on that location to try to learn all you could about that civilization or at least the environment they live in. The light coming from the planet traveled at the same speed as their radio signal so atmospheric spectra would be contemporaneous with the sending of the signal. Aliens detecting the Arecibo message would be able to look at Earth and see what it was like in 1974 when the message was sent. Knowing there's a civilization there they could keep telescopes trained on Earth to learn more about us even if they didn't fully understand the content of the Arecibo message.
It also does not matter in the slightest if there exist civilizations with esoteric means of communication. If they exist and want to talk to less advanced civilizations they'll communicate via the lowest common denominator of radio or optical transmissions. If they only want to communication via their esoteric means then they obviously only want to talk to equally advanced civilizations and we don't have a lot to offer them (at least they don't think we do). We don't really need to worry about such civilizations, we only need to concern ourselves with the ones stopping at the same bus stop as us. This is also why we tend to look for Earth-like planets when talking about extraterrestrial life. Yes some odd creatures with completely alien chemistries might exist but if we wouldn't recognize them then there is no reason to look for them right now. We can instead look for the creatures with chemistries we do understand fairly well and would recognize instantly. Also in the hunt for Earth-like planets we're not throwing away knowledge of all the non-Earth-like planets. If we find some life form in an asteroid or on the Moon with a chemistry completely unlike ours we can dig through our exoplanet archive and look for markers of such lifeforms on planets we found that were like the home of the life form we found. Just because life forms might exist that are unlike us or civilizations might exist that don't communicate like we do is no reason to assume that all life is unlike ours and all civilizations don't communicate like we do.
I'm a loner Dottie, a Rebel.
Call it the blurker hypothesis. Think about it. The universe is maybe 14b years old. Our own planet is about 4b years old. For Earth to form, there had to be a giant dust cloud full of iron and other heavy elements, which can only have come from novae/supernovae. So at least one generation of stars had to form, burn out, explode, cool to ash, and then reform into new gravity wells to form this solar system. Since this one is about 4b years old, and can be expected to make it another 4b or so, then that leaves a tidy 10b years for a previous star cloud to seed our local region of space. Seems like just enough time. So we haven't seen other intelligent life yet because we are among the first ones to emerge from the ash...