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We better hope we don't find sentient life around Alpha Centauri because that's very bad news for us. Let me explain. Imagine if there were exactly 2 sentient

by jmyeet 3y ago

We better hope we don't find sentient life around Alpha Centauri because that's very bad news for us. Let me explain. Imagine if there were exactly 2 sentient lifeforms in our galaxy, us and 1 other. What is the probability that the other evolved around our closest star in a galaxy with 100-400 billion stars? Extremely low. So, just based on that one data point the far more likely explanation is that the galaxy is teeming with sentient life. Instead of 2 lifeforms, it's more likely in teh thousands. So why is this bad news for us? Because we don't really see any evidence of spacefaring life anywhere. In Fermi Paradox terms, we think of certain events as "filters". To get to where we are we have survived a number of filters. Some are minor. Some are what we call "Great Filters", meaning life is highly unlikely to get passed eg the presence of phosphorus and other elements necessary for life as we know it. So a galaxy teeming with sentient life is highly suggestive that a Great filter is ahead of us. Consider this: many (including myself) believe that the most likely path forward for our species is in a Dyson Swarm. The ultimate problem for any civilization is energy (even resources are simply a question of energy) and living space. A Dyson Swarm solves both of these problems without requiring any theoretical or essentially magic materials. It can be built incrementally. It may also be the only viable method of producing the energy required for interstellar travel. These stick out like a sore thumb because orbitals need to dump heat. The only way to do that in space is to radiate it away. At any likely temperature for doing this, this means outputting a lot of infrared. So a star with a massive IR signature (compared to its visible light) would be an indicator of a Dyson Swarm that you cannot hide and can be seen from massive distances, particularly if you start spreading to nearby stars. A galaxy of such constructs could be seen from millions of light years away by us. Even at 1% of the speed of light, it would take no more than about 10 million years to fully colonize the galaxy. In terms of the 4.5 billion years it took us to get where we are this is a rounding error. We are likely to be able to build such orbitals within 1000 years, possibly within 100 years. So, life on Alpha Centauri would mean that rare life evolved on our closest neighbor, it became sentient and hasn't gone this route but it still in the narrow window of emergence of sentience and not becoming spacefaring, all of which is incredibly unlikely when put together, or there's a Great Filter ahead of us.

Sebb767 3y ago
> that's very bad news for us It would actually be great news. Your argumentation is sound, but in reality there either is a big filter ahead of us or there is not, this will not change at all when we find alien life. Instead, this would actually give us a solid hint as to which reality we are living in, increasing our chances to pass the filter.
- awb 3y ago
  > increasing our chances to pass the filter Why would this be the case? I think OC's point is that if the universe is teeming with non-interstellar life, then the great filter will be life's ability to spread beyond its host star, or something before that. But we already can assume that based on the lack of interstellar visitors. We'd need to discover evidence of extinct life and surmise their end to narrow down what the great filter might be and therefor have a better chance of surviving it.
rbanffy 3y ago
Fermi's Great Filters don't need to wipe out a species to work. All a filter needs to do is to prevent them from becoming an obviously detectable spacefaring colonial species. When we develop the means to live in space away from a planet, there isn't much reason to keep the habitat close to a stellar gravity well. Provided a fleet of habitats is self-sufficient, it could just orbit the galactic center and swing by star systems on its own trajectory, replenishing materials or seeding planets for building further habitats, as needed. It wouldn't be easy to detect relatively small habitats crossing interstellar space, but they could have surfaces and usable volumes, and populations, much greater than Earth has.
- jmyeet 3y ago
  So this doesn't actually help. In fact, it creates a major problem from the outset: what is your energy source? The candidates are nuclear fusion, antimatter or black holes. The last two are extremely theoretical and it's not yet certain if nuclear fusion will ever be commercially viable. But let's say you solve the energy problem. Well, you still have to radiate heat away into space so you're creating the same IR signature. In some ways it's more obvious because it's a huge IR signature with no apparent source or star overshadowing it. Now you can argue that a given civilization will remain small (and thus quiet). The reasoning with the Fermi Paradox doesn't really care about that though. If there are 3 civilizations in a galaxy then being quiet may be a factor. If there are 10,000 then what are the odds that all of them will be small and quiet? Not great, logically, given the abundance of energy that is sitting there waiting to be used with tech we already have (ie solar). Also, where is your matter coming from out in the void? As for the idea of relatively sparse orbitals (orbiting the galactic center in your example), this doesn't seem that likely for a number of reasons, primarily that solar energy is so abundant and easy to get and also the time lag in communications. Civilizations over light years may as well be different species. And again, will everyone do that?

by jmyeet 3y ago

Sebb767 3y ago

> that's very bad news for us It would actually be great news. Your argumentation is sound, but in reality there either is a big filter ahead of us or there is not, this will not change at all when we find alien life. Instead, this would actually give us a solid hint as to which reality we are living in, increasing our chances to pass the filter.

awb 3y ago
> increasing our chances to pass the filter Why would this be the case? I think OC's point is that if the universe is teeming with non-interstellar life, then the great filter will be life's ability to spread beyond its host star, or something before that. But we already can assume that based on the lack of interstellar visitors. We'd need to discover evidence of extinct life and surmise their end to narrow down what the great filter might be and therefor have a better chance of surviving it.

rbanffy 3y ago

Fermi's Great Filters don't need to wipe out a species to work. All a filter needs to do is to prevent them from becoming an obviously detectable spacefaring colonial species. When we develop the means to live in space away from a planet, there isn't much reason to keep the habitat close to a stellar gravity well. Provided a fleet of habitats is self-sufficient, it could just orbit the galactic center and swing by star systems on its own trajectory, replenishing materials or seeding planets for building further habitats, as needed. It wouldn't be easy to detect relatively small habitats crossing interstellar space, but they could have surfaces and usable volumes, and populations, much greater than Earth has.

jmyeet 3y ago
So this doesn't actually help. In fact, it creates a major problem from the outset: what is your energy source? The candidates are nuclear fusion, antimatter or black holes. The last two are extremely theoretical and it's not yet certain if nuclear fusion will ever be commercially viable. But let's say you solve the energy problem. Well, you still have to radiate heat away into space so you're creating the same IR signature. In some ways it's more obvious because it's a huge IR signature with no apparent source or star overshadowing it. Now you can argue that a given civilization will remain small (and thus quiet). The reasoning with the Fermi Paradox doesn't really care about that though. If there are 3 civilizations in a galaxy then being quiet may be a factor. If there are 10,000 then what are the odds that all of them will be small and quiet? Not great, logically, given the abundance of energy that is sitting there waiting to be used with tech we already have (ie solar). Also, where is your matter coming from out in the void? As for the idea of relatively sparse orbitals (orbiting the galactic center in your example), this doesn't seem that likely for a number of reasons, primarily that solar energy is so abundant and easy to get and also the time lag in communications. Civilizations over light years may as well be different species. And again, will everyone do that?