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# Detectable civilizations in our galaxy 4

Video transcript
I've talked a bunch about the Drake equation, or our own version of the Drake equation that starts with the number of stars in the galaxy, but I haven't given it a shot yet. I haven't tried my own attempt at thinking about how many detectable civilizations there are. So let's actually do that here. So let's just assume that there are 100 billion stars. 100 billion stars. So that's my first term right over there. Let's say that 1/4 will develop planets. And let's say of the solar systems that develop planets, on average let's say that they develop an average of 0.1 planets capable of sustaining life. Or really, that you'll have one planet for every 10 of these solar systems with planets. That's just my assumption there. I don't know if that's right. Now let's multiply that times the fraction of these planets capable of sustaining life that actually will get life. And I don't know what that is, but I hinted in previous videos that life is one of those things that it seems like if you have all the right ingredients, it's so robust. And you have life it these underwater volcanoes, you have bacteria that can process all sorts of weird things. So let's say that probability is pretty high. Let's say that is 50%, or half of the plans that are capable of getting life actually do have life. I would guess that that might even be higher. But once again, just a guess. Now we have to think about of the life, what fraction becomes intelligent? What becomes intelligent over some point in the history? Well, I'll say it's a tenth. A tenth of all-- maybe if the asteroids didn't kill the dinosaurs, it wouldn't have happened on Earth. Who knows? Or maybe we'd just have some very intelligent dinosaurs around. We don't know. And maybe there's other forms of intelligent life even on our own planet that we haven't fully appreciated. Dolphins are a good candidate. Some people believe that octopuses, because they have such flexible arms, there's a theory that they could develop eventually the ability to kind one day, if their brains mature, and all of the rest, make tools the same way primitive primates eventually were able to have larger brain sizes and actually manipulate things to make tools. So who knows? I don't want to get into all of that. So there's a 1 in 10 chance that you get intelligent life, and then assuming that intelligent life shows up, what fraction is going to become detectable? I don't know. I don't know whether dolphins will ever communicate via radio or not. So let's just say that is-- I don't know. Let's say that is another 1 in 10 chance, or I'll say 0.1. And then we have to multiply it times the detectable life of the civilization on average. Once again, huge assumptions being here, but the detectable life of a civilization, let me just put it at 10,000 years. Either they destroy themselves, or they get beyond that type of radio type communication, electromagnetic type communication. Maybe they start doing all sorts of weird, wacky things. Probably it won't take you 10,000 years to even progress it. That might take you less time. But let's just do this just for the sake of fun. And then the lifespan of your average star, that's probably one of the things that we have the best sense of. So on average, let's put it at 10 billion years, 10 billion years. So let's calculate all of this. Let's get my handy TI-85 out. And so we're going to have 100 billion. That's 1 times 10 to the 9th. Sorry, that's 100 times 10 to the ninth. So let me clear it. Or you could have 1 times 10 to the 11th. That is 100 billion times 0.25 times 0.1 times .05 times 0.1 again, times 0.1 again, times 10,000 divided by 10 billion. So times 10,000, 1, 2, 3, divided by 10 billion. So that's one 1e10. 1 times 10 to the 10th power. 1 with 10 zeroes. So let's see what we get. We get 12.5, which is kind of a neat number, but these are heavily dependent on this. So we're saying if given these assumptions, there should be 12.5 detectable civilizations in our galaxy right now. So the question is, why aren't we detecting it? Maybe their radio signals, maybe their electromagnetic waves are getting to us, but we can't differentiate it from noise right now. And that's what the whole SETI project's all about, of trying to keep track of all this information, all of these radio waves, and electromagnetic waves that are coming from outer space towards Earth, and seeing if any of them actually have any non noise signal, that actually look like they're being generated by some type of intelligent civilization. So maybe we're getting them, and we're just not detecting them, or maybe something else is at play. Maybe we've overestimated one of these. Maybe there is a lot a life, but maybe they're not using electromagnetic waves to communicate. Maybe that's some type of primitive way of communicating. Maybe they start doing telepathy, or something crazy, or they start using some type of quantum thing that allows them to communicate more directly without having to wait for the speed of light. That is a very slow way to communicate. And it is a slow way, frankly, if you're trying to communicate across solar systems, and stars, and planets, or even across galaxies, one could imagine. So maybe we're just kind of at a transition state of communication, that electromagnetic waves, radio and all the rest is just a transition state. Maybe in 100 years we'll figure out another, better way that's not detectable in our traditional ways. Maybe we're being bombarded with another type of communication mechanism that we're just not ready to perceive yet. Who knows, but it's just a fun thought experiment to say that hey, given these assumptions, there should be at least a couple of civilizations, or a handful of civilizations that we might be able to detect.