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Disagree. Life on Earth showed up about as soon as it could. That says the development of life isn't a likely limit. We see only one form of life because hav

Disagree. Life on Earth showed up about as soon as it could. That says the development of life isn't a likely limit. We see only one form of life because having a head start let it outcompete everything else. We appear to be alone. That says something (or some combination of things) in the process of developing into a starfaring civilization must have billions-to-one odds against it. It's not planets--we see tons of planets. Earth-like ones don't show up much--but our detection techniques aren't very good at seeing Earth-like planets so we can't conclude much from that. The rapid appearance of life on Earth says that's not a likely barrier. Looking at history we have two candidates: the development of multi-cellular life and the development of intelligence. Both took billions of years on Earth. Note that humanity just squeaked in under the wire, about 99% of time Earth would be capable of evolving intelligence is already past. The sun has been slowly warming, this has driven more CO2 into limestone, offsetting the warming. This buffer has almost pegged, once it pegs solar warming turns into planetary warming and Earth is no longer suitable for species with long life cycles. If we are lucky we are extreme outliers in how fast one or both of those steps happened and the barrier is behind us. (This shouldn't be discarded on improbability--observer effect. Only a planet where that happened could develop a species that could note the issue.) If not, the limit is in the future. Either we destroy ourselves or we somehow turn inward and ignore the stars. Unfortunately, probably says it's one of the latter. It is possible for there to be a galactic empire and yet we exist--quarantine hypothesis. There's a galactic empire that strictly avoids any star systems with worlds where life can arise. However, such a galactic empire should be detectable anyway. A star wrapped in a dyson swarm will show a spectrum unlike anything we can see in the sky. From this we can conclude there are no dyson swarms in any part of the universe we can resolve stars. Earth shines in the radio spectrum. An ET pointing a radio telescope at us isn't going to be able to decode much of anything (any more than we could listen to a million voices at once) but they can see the energy.

qayxc 4y ago
The very concept of a "Galactic Empire" is flawed as soon as you take scale and spacetime into account. The first major obstacle to the concept is distance. It'd take centuries to get even to the nearest off-world colonies and even simple things such as common time keeping become a challenge. Communication basically breaks down completely once you get to distances beyond just a few light years: consider a "small" interstellar kingdom within a 100 ly radius. The central world will always necessarily be 100 years (in terms of just time) away from the outer worlds. Something happens on the outer rim, the central world won't be able to know about it until 100 years after the fact. So in essence, every world that's more than a few (e.g. less than 5 or so) light years away is practically isolated from the rest - both logistically and from a communications perspective. It's very hard to come up with any way of describing such a scattered collection of islands as one coherent civilisation. Another issue is the colonisation process itself. It's virtually impossible to find a nearby 1:1 copy of a world that matches the point of origin of the civilisation. Therefore, terraforming (a lengthy and resource intensive process) or genetic modification would be required. The latter will occur naturally anyway, since some physical attributes of the target world simply cannot be changed without god-like powers (e.g. orbital parameters and gravitation). This means you'd end up with sub-species pretty quickly that won't share the exact same biology and probably have a very divergent culture as well due to being so isolated. You'd have to come up with some really strong arguments as to how and why - given these circumstances - even "just" interstellar civilisations should be possible in the first place.
- Nomentatus 4y ago
  Because it's cheap. You only pay once for one small vehicle [1], and its reproduction at the first destination sets off the whole rest of the process. I wouldn't advise sticking to gravity wells. Or even bothering with them. Subspecies and cultural divergence can be seen as a solution, leading to more innovation that can be shared at the speed of light. [1] https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/abs/on-the-interstellar-von-neumann-micro-selfreproducing-probes/654B1F254BA4F328E52AD748158A59F5 https://www.cambridge.org/core/journals/international-journa...
  - qayxc 4y ago
    But micro-scale von-Neumann probes wouldn't be building civilisations either - they'd be l'art pour l'art - building more Dyson Swarms for the sake of building more Dyson Swarms. The paper also only considers microscopic probes "invading" HII regions (i.e. hydrogen-rich star forming regions), not colonising space. By "cheap" you also left out the author's assumption that "the propulsion system will require a tiny fraction of the total gained mass to convert into energy, which we assume could not be a problem for a Type-II civilization." So they already start with a Type II civilisation that basically dismantled part of their planetary system to reach that state in order to... build probes that construct more Dyson Swarms? Still doesn't sound like a very compelling argument to me. The paper also doesn't deal with the actual expansion aspect - only with the detectability of micro probes moving through- and replicating within star forming regions, i.e. not places you'd actually want to colonise - neither inside or outside of gravity wells. > Subspecies and cultural divergence can be seen as a solution, leading to more innovation that can be shared at the speed of light. You seem to greatly underestimate the vastness of space. Even a tiny (by Fermi-Paradox standards) interstellar realm would have worlds hundreds of lightyears apart. There's not much use in sharing "innovations" if they arrive after 500 years - not much innovation left after such a long time (unless you assume that one side stops innovating entirely for some weird reason, yet keeps listening for signals), plus it'd become increasingly harder to even keep a common cultural understanding given the temporal and spatial distances. Language changes over time, for example.

qayxc 4y ago

The very concept of a "Galactic Empire" is flawed as soon as you take scale and spacetime into account. The first major obstacle to the concept is distance. It'd take centuries to get even to the nearest off-world colonies and even simple things such as common time keeping become a challenge. Communication basically breaks down completely once you get to distances beyond just a few light years: consider a "small" interstellar kingdom within a 100 ly radius. The central world will always necessarily be 100 years (in terms of just time) away from the outer worlds. Something happens on the outer rim, the central world won't be able to know about it until 100 years after the fact. So in essence, every world that's more than a few (e.g. less than 5 or so) light years away is practically isolated from the rest - both logistically and from a communications perspective. It's very hard to come up with any way of describing such a scattered collection of islands as one coherent civilisation. Another issue is the colonisation process itself. It's virtually impossible to find a nearby 1:1 copy of a world that matches the point of origin of the civilisation. Therefore, terraforming (a lengthy and resource intensive process) or genetic modification would be required. The latter will occur naturally anyway, since some physical attributes of the target world simply cannot be changed without god-like powers (e.g. orbital parameters and gravitation). This means you'd end up with sub-species pretty quickly that won't share the exact same biology and probably have a very divergent culture as well due to being so isolated. You'd have to come up with some really strong arguments as to how and why - given these circumstances - even "just" interstellar civilisations should be possible in the first place.

Nomentatus 4y ago
Because it's cheap. You only pay once for one small vehicle [1], and its reproduction at the first destination sets off the whole rest of the process. I wouldn't advise sticking to gravity wells. Or even bothering with them. Subspecies and cultural divergence can be seen as a solution, leading to more innovation that can be shared at the speed of light. [1] https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/abs/on-the-interstellar-von-neumann-micro-selfreproducing-probes/654B1F254BA4F328E52AD748158A59F5 https://www.cambridge.org/core/journals/international-journa...
- qayxc 4y ago
  But micro-scale von-Neumann probes wouldn't be building civilisations either - they'd be l'art pour l'art - building more Dyson Swarms for the sake of building more Dyson Swarms. The paper also only considers microscopic probes "invading" HII regions (i.e. hydrogen-rich star forming regions), not colonising space. By "cheap" you also left out the author's assumption that "the propulsion system will require a tiny fraction of the total gained mass to convert into energy, which we assume could not be a problem for a Type-II civilization." So they already start with a Type II civilisation that basically dismantled part of their planetary system to reach that state in order to... build probes that construct more Dyson Swarms? Still doesn't sound like a very compelling argument to me. The paper also doesn't deal with the actual expansion aspect - only with the detectability of micro probes moving through- and replicating within star forming regions, i.e. not places you'd actually want to colonise - neither inside or outside of gravity wells. > Subspecies and cultural divergence can be seen as a solution, leading to more innovation that can be shared at the speed of light. You seem to greatly underestimate the vastness of space. Even a tiny (by Fermi-Paradox standards) interstellar realm would have worlds hundreds of lightyears apart. There's not much use in sharing "innovations" if they arrive after 500 years - not much innovation left after such a long time (unless you assume that one side stops innovating entirely for some weird reason, yet keeps listening for signals), plus it'd become increasingly harder to even keep a common cultural understanding given the temporal and spatial distances. Language changes over time, for example.