I think that question was sufficiently addressed in the first ten or so posts.
Stranger
The gains from communication are not just in parallel, but in serial. If every human had to start from scratch, there’s no way we’d ever have made it to computers and space probes. But when Euclid and Archimedes and Galileo and Newton and Maxwell and Einstein and Turing and Goddard all communicate to me, I can pick up where they left off.
And on the other point, I’m a teacher. It is literally my job to share my memories, experiences, and mental techniques with other humans, and I happen to think that I do my job fairly well. I don’t do it perfectly, of course, but that’s not necessary: Even the imperfect communication of those things is enough to vastly improve human capability.
Nonsense. By this reasoning, if intelligent life is insanely rare, it follows that its precursor – a star that remains stable for a few billion years – must also be pretty rare, which is obviously not true.
I believe life may be common in the universe, but a communicative civilization that could or would communicate with us may be virtually zero.
I’m no expert in this area so I welcome our resident spacemen (e.g. Stranger on a Train) to correct any of my facts, or assumptions.
I think the number of active, communicative civilizations in our galaxy (or any galaxy) is not zero, but quite small—maybe 3 and we’re one of the 3. Perhaps one of the others could communicate with us, but chooses not to and the other one is on the other side of the galaxy and their signal just hasn’t reached us, yet.
If there are an average ~100-billion stars in each galaxy, that’s a big number, but it’s not an astronomical number. Put it in perspective: If stars were being sold a dollar a piece, Bill Gates could buy most of the stars in the Milky Way. And, if years were being sold a dollar a piece, he could go all the way back to the Big Bang and have enough money left to buy a few more universe timespans. These are manageable numbers, not approaching infinities.
But, for the sake of argument, let’s assume an infinitely large universe. Does that increase our odds of ever receiving a signal from an extraterrestrial? No, not in the least. The edge of the observable universe is ~47 light years away. There’s no way we can receive a signal from any galaxy beyond that. Bill Gates could almost afford $2 for each of those light years. It’s a manageable number, not approaching infinity.
How about all those galaxies that are receding away from us within the observable universe at >c? It’s the great majority of them. The light we receive from them was emitted before they started expanding away so quickly, closer to the time of the Big Bang than today. I don’t believe any civilization could have developed communicative technology in that young a universe. And any signal sent from them after that will never reach us (unless they can signal faster than light). Galaxies beyond ~14.7 billion light years are receding away from us >c. I surmise that a high percentage of galaxies within that boundary are still receding away from us fast enough to make signal contact from them extremely unlikely—or, it may take billions of years from now for us to receive them.
So, there may be billions upon billions of advanced communicative civilizations in the universe that would like to contact us, but they just can’t. The vast majority of our universe is too far away for that to occur.
But, the Drake Equation specifies the Milky Way galaxy and high estimates reach into the tens of millions of communicative civilizations. But, like I said, I think there’s only 3; call me a pessimist. I’m not a pessimist on the emergence of life, however. It would not surprise me if we do find other life even within our solar system.
I don’t view the Fermi Paradox as a paradox at all, even if the universe is teaming with intelligent life. As mentioned, the vast majority of them would not be able to signal us even if they wanted to because of the distances involved. For, another thing, they may not want to signal us even if they could.
I don’t think they would refrain from contacting us for the oft mention reason that they’d be afraid we’d zip over to their world and hurt them (that is very likely). I just don’t believe they have anything to gain by emitting signals that can reach us.
We humans are quite young in the intelligence game and younger still in our embracement of science and technology. We’re still very curious, like monkey’s poking sticks at things to see if they move. We’re also very loud and boastful: hey, look at us universe, we’re here and we want you to notice us! I don’t believe a super-intelligent species of, say, insect or reptile people would make that a prerogative.
My guess is that this is dangerously curious, boastful way about humans is just a juvenile stage we’re going through and that most super-intelligent species take a much more pragmatic approach to existence. I also believe whatever communicative technology they’ve developed is most likely more narrow focused (like a laser beam) than our own propagating radio signals traveling willy-nilly into the great beyond.
If they want to communicate with another star system in their own galaxy, they’ll just focus the signal directly to them. They may very well want to communicate with their neighbors for pragmatic reasons, because they have something tangible to gain.
But, why would they want to communicate with us ugly creatures from another galaxy? To boast? To expect some sort of two-way conversation? To ask if we have Bar-B-Que ribs that they could travel tens of billions of miles to take out? What’s in it for them?
Curiosity? I’m sure they have their own Drake Equation and know better than us the odds of intelligent life in the universe. Why would they need to confirm it over and over again when they have nothing to gain?
I don’t believe the Drake Equation properly addresses the likelihood that a significant % of super-intelligent species within our zone of communicability may not have the technological means to emit signals that can reach us, or that they may not have a desire to do so. What if most of the intelligent species in the universe live underwater on liquid planets? Or, worse still under a mile of ice? Could they build a device to signal the stars? They may not know that stars even exist, living under all that ice. And, why would they signal us? So we can come ice-fish them out so they can flop about like boated flounder on the ice surface? I believe there are a lot of probable scenarios like that, which the Drake Equation doesn’t account for.
But, life on Mars? Maybe. Life on the Jovian or Saturian moons? Maybe even more likely. I’d love to be around to witness it.
If that were true, humans would fill all the space reachable with current technology, thickly populating deserts, jungles, sea floors, etc. This has not happened to any significant (i.e. an alien landing at some random place in a desert, jungle, or ocean would readily note signs of habitation) extent.
If anything, the opposite seems to be true – life appeared on Earth very soon (on a geological timescale) after it stopped getting bombarded by a steady rain of planet-killer rocks, and then went billions of years without developing much in the way of intelligence.
Jumping to that conclusion is almost as reckless as ignoring a rusty-nail puncture wound.
I can’t speak for Habeed, but I think that at least some of this speculative, um, stuff may be relevant.
Here’s Nick Bostrom on the concept of the Great Filter, which is a kind of extension of the Fermi Paradox.
Some of you may be familiar with Bostrom’s argument, others might need to read the essay here
Whether it is relevant or not I can’t really be sure yet - but it may become relevant if we do indeed find life on Mars, and especially if it turns out to be entirely unrelated to Earth life. This would suggest strongly that life is widespread in the universe.
Tying this into the OP somewhat - if life on Mars is totally unrelated to Earth life, this could make it far more difficult to detect - but it would almost certainly make it far more significant as well. We could easily get a false negative if we only send limited experiments to the Red Planet which are constrained by our expectations.
Exactly. My arguments could be summed up as :
We humans right now can’t go fill the observable universe with ourselves. It would cost us like a quadrillion dollars to build a starship, and it would take about 1000 years to reach Alpha Centauri, and would probably break down in flight or never make it. Even if it did make it, it would be like 30 generations later, so there would be 28 generations of people who have to live their whole lives and die of old age on the ship, and the people who launched the ship would get no reward themselves.
And even that’s speculative…reaching Alpha Centauri that amazingly fast would require something like a fusion exhaust engine, and if you notice, we don’t even have fusion working well enough to be able to send exhaust out the back of a ship.
But these problems may not be as insoluble as they sound. If we could just get really smart and good at making things, it wouldn’t take a quadrillion dollars, because some of us would be super-geniuses with the equivalent brainpower of entire universities crammed into a single being. It wouldn’t take nearly as much to make things, since we need only build 1 small factory that can make anything imaginable and have it copy itself exponentially until building 10 kilometer long starships is easy. And since we wouldn’t die of old age, being based in circuitry similar to computers but optimized to act like a brain, we just manufacture new circuitry and copy ourselves as data files to new hardware before the old hardware wears out.
You guys can call all that stuff “speculative” if you wish. We have working, real and physical, examples of everything I named. Our electric charge model for human neurons can be duplicated using computers and we **do **have dedicated brain emulation chips and we **do **have massive supercomputers, demonstrating the feasibility of building an even bigger one. We do have self replicating factories - our human bodies are such machines in themselves. Also, if you think about it for a bit, you would realize that our factories right now, collectively, are self replicating already, they are just gigantic. And that fusion thing…well…we have it working in a bomb, so it can be done, it’s just really hard to get working in something stable.
So if that’s all true, then why hasn’t someone else done the obvious, and when we look out our telescopes, the sky is alive with gamma ray trails from antimatter starships and all the stars have suspicious shading from dyson swarms?
Just had time to skim the PDF, but Bostrom’s argument seems to be: if life is found on Mars, it implies that life must be ubiquitous throughout the universe. If that’s the case, then something (the Great Filter) is preventing life from evolving into intelligent beings, capable of signaling us. And, since we’ve received no signal, it implies that the Fermi Paradox (where are they?) is correct and our future looks bleak.
This isn’t a problem if you accept a low number on the Drake Equation, as I do.
Those Martian trilobites were just born on the wrong planet and they went extinct before they could develop opposable thumbs to build spaceships to leave their dying planet. Sucks to be them.
Now, if we find human skeletons next to iPads buried in the Martial soil, then maybe we have something to worry about.
Right, the core question is whether we are past the Great Filter yet or not. It’s possible that the Great Filter is the emergence of life itself, in which case, we’ve been past it for billions of years, and don’t have to worry about it any more. It’s also possible that it’s something like photosynthesis, or eucaryotic cells, or something else that we’re already past, in which case the conclusion is much the same. But it might also be that the Great Filter is, say, that civilizations tend to destroy themselves once they develop nuclear power. In that case, we need to worry.
Of course. How silly of me. Here we are in a thread full of “Let’s go to Mars” and you conclude that we have chosen to stop spreading. You also mistake a temporary economic condition for a permanent choice on population growth.
It only takes one aggressively pro-growth species to dominate an environment. Our empirical data shows just that on a planetary scale and not just once but repeatedly. We don’t need particularly fantastic technologies to let them do it on a galactic scale over a period measured in millions of years. If you really believe life is common, that just makes it more likely to happen.
The scary thing about the ‘great filter’ concept is that we don’t know if the ‘great filter’ is behind us - a test we passed, a cosmic sterilizing event that we narrowly escaped, or some intrinsic property of life that causes it to remain simple in the vast, vast majority of cases. Or… The great filter is ahead of us - there’s something in the universe that generally kills civilizations before they gain the ability to travel between the stars.
If the former, then we’re really lucky. Go us. If the latter, then very soon we are in for a world of hurt.
But really, you don’t need to invoke any of this, so long as the Drake Equation has terms that can reasonably lead to a value of approximately 1 for the number of technologically advanced civilizations in the galaxy. As there are still some terms in the equation that are totally unknown such as the probability that extra-terrestrial life would evolve into an intelligent, starfaring society, it’s entirely possible that life is ubiquitous, but achieves interstellar travel or communication ability so infrequently that having even one in a galaxy is very lucky. We just don’t know.
Getting back to discovering Martian life… One of the problems we would still have is to determine whether it’s truly an example of life emerging twice, or whether there is enough cross-contamination between Mars and Earth that life could have been transported from one to the other, which would then prove exactly nothing in terms of how likely it is for life to appear. Or, life on Earth and Mars both started somewhere else - the panspermia theory. Given that long-period comets appear to be even more rich in volatiles and complex carbon compounds than we thought they were, I think that’s still an open theory.
As for the Fermi Paradox, well… That still requires a number of assumptions about the nature of intelligent species, the ability to build self-replicating probes, the timescales required to populate a galaxy, etc. It’s a great tool for anchoring speculation, but it proves exactly nothing about anything at this point. At best it helps us focus our thinking about the problem.
One of the intriguing changes to SETI is that recently they have started looking at not just radio waves, but optical signs of advanced civilizations like Dyson Spheres. There was recently a survey of nearby galaxies looking for these ‘type III’ civilizations, but none have been found.
However… There are some stars in the Kepler dataset that have some strange anomalies we don’t yet understand. For example, KIC 8462852.
Basically, Kepler was designed to watch a huge field of stars, looking for dips in their light output indicative of some kind of transit or eclipse event. A dimming of the star on an even, regular interval is consistent with something orbiting the star - a planet, another star, etc. This is how we’ve been finding most of our exoplanets.
The star in question, through, has a really strange light curve. It has dips in it of different sizes, occurring on irregular intervals. We don’t have any explanation for that. One thought was dust clouds of irregular composition, such as what you might see in a protoplanetary disk. There are two problems with that - if a lot of dust was absorbing light from the star, we would expect it to radiate in IR and we’d seee that in the spectra of the star. We don’t. Another problem is that the star is old, and shouldn’t have a protoplanetary disk around it at all.
Another possibility, and the one they settled on, is that perhaps a star recently passed through this star’s Oort cloud, and what we’re seeing is a rain of comets passing across the star’s disk. But that, and every other explanation they’ve come up with so far, is exceedingly unlikely because such an event would be fairly transient and we’d have had to be looking at the star at a very short window in time between the start of the event and the time it would take before it’s finished.
The other possibility is not mentioned in the paper, but IS discussed by the scientists involved, is that what we’re seeing are artifacts of an advanced civilization: Huge solar collectors, for example. Or massive orbital habitats. This scenario is considered plausible enough that SETI is booking radio telescope time in January to observe this star in detail and see if there are any anomalous radio waves coming from it.
There are several other stars in the Kepler set that have somewhat similar anomalies, making the odds of it being a random comet train less likely. But there could be many other natural explanations for this we just haven’t figured out yet. Nonetheless, it’s a fascinating story worth following.
Here’s a somewhat sensational article in The Atlantic about it: The Most Mysterious Star in Our Galaxy
I think you have to have a little more respect for the difficulty of travelling to the stars. They are a LONG way away. They require huge amounts of energy to get to in any kind of reasonable time. Once there, it would be very hard for the original civilization to exploit the new real estate.
The supposition behind the Fermi Paradox is that we will eventually be able to make self-replicating probes, and if we can do it, someone else should have already done it. And once you unleash self-replicating probes on a galaxy, then in fairly short time on cosmological time scales they should basically infest it all like a virus spreading.
There are a hell of a lot of assumptions baked into that. First of all, a self-replicating probe would not just have to be smart, it would have to be able to locate a suitable planet or other body that has the raw materials it needs, then it would have to be able to land on it and build a manufacturing facility of some kind, build new interstellar probes and then launch them. It would have to be able to do this after having travelled for hundreds or thousands of years. That’s a technological capability so far in our future we have no idea if it can even be done.
And if we could do it, the rate of expansion would greatly depend on the success of each probe in replicating itself. For an exponential growth pattern to emerge, on average each probe has to create more than one daughter probe. We have no idea how likely that is, how long it would take a civilization to attain that capability, or whether a civilization that gains that level of ability would even be interested in randomly colonizing the galaxy.
Go look in the mirror. Go look at a satellite photograph of China.
You know what you just saw? The strongest form of scientific proof of anything : proof of existence. The only piece missing from said self replicating probe is an engine that can get the probe to another star is some remotely feasible timespan. Go bring up a video clip of a fusion bomb going off. Ok, done.
The fact that we don’t quite have said probes in the form they need to be in is meaningless : we have overwhelming evidence showing they are both feasible and similar systems as possible. If you can’t see it, that’s ignorance on your part, not a shortage of evidence.
As for the last bit : as I mentioned before, it only takes there to be a pool of several civilizations or several individual competing groups who can make such a probe. If one of them launches the probe, or better still, several launch probes, and probes that copy themselves get to make variants of themselves that may be modified slightly…you can clearly see what evolutionary forces would do over time in such a universe.
So, ok, what *could *the reason be? Well, there could be a reason out of left field. The problem with my statement is there could be hard laws of physics stopping a self replicating probe…they just must be laws that we don’t know and never discovered. Maybe there’s invisible brick walls out in interstellar space blocking starships. Maybe sentient beings actually have magical souls, so AIs can’t work. Maybe factories today can’t be made any smaller because God personally prohibits it. But if you speculate based on **known **knowledge, we are quite certain said probes as possible.
This is nonsensical. So, because people can breed, it is therefore obvious that we can build machines that can travel to another star system, set up manufacturing, and build copies of themselves and launch them into interstellar space. Is that it?
I have no idea what your point was about the fusion bomb.
The problems that have to be solved to be able to build interstellar self-replicating probes are vast, and some of them may be insurmountable. And again… It doesn’t have to be impossible - it just has to be hard enough that the exponent remains less than one for the rate of expansion.
We aren’t talking about hundreds of years before we have this capability, btw. When each ‘iteration’ of your experiment in interstellar self-replication takes thousands of years, you could be talking about millions of years. It assumes that we can build a general AI capable of handling the numerous unknowns of a new star system. It assumes that the probe can assemble the resources necessary to replicate itself. It assumes that it can bootstrap a manufacturing facility. It assumes that it can find and mine the resources required to propel the new probes. Etc. There are unknowns around all of these issues.
Given that we’ve never travelled to another star system, that we don’t know how to build a strong AI or whether it’s even possible, that we’ve never built a self-replicating machine anywhere near the complexity of so much as a transistor radio… I think it’s safe to say that there’s still a shortage of evidence.
Jesus. This is science fiction. We have no idea if other civilizations exist, and if they do, whether they think even remotely like us. Dolphins are pretty intelligent - so are African Gray Parrots. Neither is intent on colonizing the universe. It may be that the way our brains are wired is very unique, and other intelligences ‘out there’ could be motivated in completely different ways. We just don’t know.
That’s a ridiculous statement. ‘Certainty’ and ‘unknown’ do not belong in the same sentence. Until we have actual evidence that it’s possible, the correct answer is that we don’t know if it’s possible. Not that we’re ‘certain’ it’s possible - unless we find out something we don’t know.
I’m not really a spaceman (never been above the Karman line although I’ve been a participant in programs to seen a few dozen objects into orbit or to the moon) and I don’t claim to be an expert on xenobiology, but I’ve read and thought about it a bit. One of the things to consider is that we’ve had the ability to receive and interpret one type of signal (radio) for a period of no more than a single century (generously speaking).
That means our entire radius of being able to look for life even if they were deliberately trying to contact us via radio is somewhere in the vicinity of 100 light years at most. That is 0.00005% of the volume of our galaxy, and not even the most dense part by far. We can see stars with sufficient resolution to detect some kind of interplanetary industry (e.g. specific spectral lines of fusion engines, maybe out to 1000 light years, or about 0.005% of the volume of our galaxy, and about a quarter or more of the galaxy is completely occluded by dust and the core. We’ve also been looking for about 0.0000008% of the life of the galaxy. Even if we assume that complex life could only form after there was sufficient metallicity to create Population I stars and at least a few billion years into that, we’re still looking at a tiny fraction of a percent of time that other civilizations could rise and fall, or evolve past the crude scheme of energy usage used in the Kardashev scale. It is quite possible that more advanced intelligence life–even civilizations only a few millenia beyond our current progression–could be as far beyond us as we are to ants, and that they wouldn’t even regard us as having sufficient communication or cognition to engage in any useful interchange. (Especially if they’ve seen Twitter feeds or talk radio.)
Basically, we can draw the same conclusions about life in the galaxy from existing data as we could of the history and variety of cuisine of New York from ordering room service in the hotel room. The galaxy could be liberally teaming with life and we may have no clue whatsoever. Or it could be as barren and sterile as our moon. But given the scale of the place and the presumed variety of both environments and ways in which life could form, I tend to lean subtantially to the former.
This is very true, but we can’t really concoct useful experiements for forms of life that we have no idea about. All we can really look for are chemical reactions or products that appear unnatural, or energy release or absorption with no reasonable physical explanation.
If we ever expand our horizons to physically exploring beyond our solar system, in the absence of any science fictional superluminal transportation, it will likely be with some kind of quasi-organic self-replicating probes, e.g. Dyson’s “Astrochicken” concept rather than via mechanical probes, giant space arks, or any of the other tropes of science fiction. The time span for travel, scale of both distance and energy, and required reliability to function for millenia to reach even the nearest stars is an enormous hurdle for any foreseeable technology.
Stranger
No. My point is the following :
Probe is the wrong word. Current knowledge knows you can build a machine that consumes about 10 watts and weighs about a kilogram that is fully sentient. It isn’t an autonomous system, it’s a being that, combined with enough blueprints and the efforts of similar beings, can solve all the challenges it finds at another star.
The fact that we, humanity, don’t quite have the pieces yet doesn’t mean that we don’t look in the mirror and see such machines daily. We also know self replication of the most complex systems on earth is possible, again, because we have mirrors.
As for how a real probe would work : it would be a machine that somehow copies itself at the molecular level. It would contain a brain with blueprints for an entire technological civilization and would be fully sentient. It would contain machinery to consume basically any sample of rock and break it down to constituent atoms.
I’ve fought ignorance as hard as I can, but I can’t really fight any further. If you really think that you can’t test such a “probe” by having it set up shop at asteroids in the solar system, without waiting thousands of years, or that self replicating nanotechnology is impossible despite your own body having such machinery, or that fusion bombs don’t demo that a fuel source needed to get a rocket to a reasonable fraction of the speed of light exists, well…I guess the discussions over.
This discussion isn’t about whether we can write a check and get interstellar probes tomorrow, or within your lifespan. If it takes 1000 years to develop the underlying tech, that’s a blink of an eye. Humanity has been around for far longer, and life on earth has had 3 billion years. If it can even be done in 1000 years, the question is why someone else isn’t thousands of years ahead of us and showing the evidence of their activity in a form we can’t miss. So any “technical” arguments you make need to be saying it’s impossible, period, and I’m saying you already can see it’s possible.
By the way, here’s what we “know”.
- Matter can reach other stars. How do we know? Because there are elements on earth our Sun can’t make
- Complex self replicating machines are possible. How do we know? Because life is such a machine.
- Self replicating factories are possible. How do we know? Because every part used in any factory on the planet can be made in another factory, therefore, it is possible to build a mega-factory that copies itself.
- Sentient self replicating machines are possible - see mirrors.
- Separation of asteroids into constituent elements is possible - see mass spectrometers, plasma furnaces
- Communication between stars is possible - see radios. So even if such a “probe” needed more knowledge, it could download it, albeit it would have to sleep for a decade or so waiting.
- It is possible to control the same nuclear reaction that fuels stars, and to force the products from said reaction in a particular direction. See existing fusion experiments. No, such a fusion drive doesn’t even need to have positive energy gain, it’s just convenient if it does.
All this combined is stuff we know, and are certain of. They tell us an interstellar probe shaped object, due to #1-#7, could reach another star, eat the asteroids, and eventually make more of itself.
The ball is in your court to show a reason such a system can’t be built. It doesn’t matter that we can’t build one now, just that it’s possible.
I’m not sure what distinction you’re making, here. If there’s some factor in the Drake equation that’s low enough to result in only one civilization per galaxy, then that factor is the Great Filter.
And Habeed’s point is that the “self-replicating probe” could be a tin can full of humans. We know that humans can self-replicate, and we know that we can build more tin cans. Maybe our expansion will take the form of a colony ship landing on a new world, taking 50 or 100 years to get their industrial base established, and then building and launching two more colony ships. Once you can build just one colony ship, exponentially growing them in this way is easy.