3 ms·

Because to power a type 2 civilization you need around 4 * 10^26W (as the paper states). Over a year that is around 10^31 kWh worth of energy. Assuming fusion c

Because to power a type 2 civilization you need around 4 * 10^26W (as the paper states). Over a year that is around 10^31 kWh worth of energy. Assuming fusion can transform 1% of the input mass in energy you need ~ 1.4 * 10^19 kg per year. To put that number into perspective mount Everest weights 2.7×10^14 kg [1] so thousands Everests worth of mass. That is a lot of mass to extract and transport to the power stations (accelerate, decelerate). So it just makes sense to only needing to build the facilities to collect the power from existing sources (stars, black holes) without the logistics of transporting the fuel. Moreover, the space around a star or black hole is real estate that would go unused otherwise, while asteroids, moons, ... are more likely usable by such an advanced civilization. [1] https://www.quora.com/What-would-the-estimated-weight-of-Mount-Everest-be https://www.quora.com/What-would-the-estimated-weight-of-Mou... (I took the highest estimate in the first answer)

snek_case 5y ago
You also have to realize that the Kardashev scale [0] is something invented by someone in 1964. It's more a science fiction idea than some law of nature. We can't take for granted that this is some natural progression for every technological civilization. > it just makes sense to only needing to build the facilities to collect the power from existing sources (stars, black holes) without the logistics of transporting the fuel. Yeah OK, but then you have to transport your entire reactor to the fuel. For that matter, you also have to transport the energy where it's needed once you've harnessed it. [0] https://en.wikipedia.org/wiki/Kardashev_scale https://en.wikipedia.org/wiki/Kardashev_scale
PaulHoule 5y ago
The counter is that most of the usable mass in the universe is in interstellar objects such as comets and free planets which are 50% water ice or so, rich in organic materials and can be consumed completely to build habitats. With D + D fusion (easy to believe compared to CNO) an interstellar civilization could be essentially independent of stars. I'm sure part of the resolution of the Fermi paradox is that dry inside-the-frost-line planets like Mercury, Venus, Earth and Mars are not the generic places you find life. If things were a bit different I could see a would-be Galileo on an less cooked version of Io or a more cooked version of Europa who looks at the Earth with a spectroscope and sees oxygen and has a huge amount of trouble with his local "church" that thinks it is impossible to have life on a planet with less tidal activity, less radiation, inside-the-frost-line dryness, etc. Even if creatures like us became interstellar we might have millions of kilometers of condominiums and shopping malls in the oort cloud and could care less about inner solar system planets.
SkyMarshal 5y ago
Any idea if there’s enough construction material in any given planetary system to construct a Dyson sphere around its star? Seems like it would require, at minimum, several planets worth of raw material.
- serverholic 5y ago
  In reality you probably wouldn't see a dyson sphere but a dyson swarm instead. With that you just need millions of thin sheets of material to reflect energy.
  - TremendousJudge 5y ago
    >In reality Why do people keep insisting on the Dyson concept as though it was real, even though it's just the fanciest thing we can imagine with our current understanding of physics? The same way in the 19th century nuclear power couldn't be envisioned, there's definitiely a bunch of technology we don't know about now that an alien civilization could be using; we could even be observing this right now and we would be none the wiser. Talking about Dyson shperes, or swarms, or rings, and then concluding that there's now alien civilzations because we can't see them is just anthropocentrism, failing to consider other possiblities
    - JohnJamesRambo 5y ago
      It’s possible this is as advanced as we can get. Innovation seems to be slowing down don’t you think? At some point you have exhausted the laws of physics and this is what you’ve got to work with. https://www.cold-takes.com/this-cant-go-on/ https://www.cold-takes.com/this-cant-go-on/
      - TremendousJudge 5y ago
        It's possible, but I find it extremely unlikely. The "end of physics" has been predicted several times, even in the face of obvious unanswered questions, like today's "what's the deal with dark matter and dark energy?", "can chaotic processes be understood?", "what even _is_ gravity?" When in the past, unanswered, mystery questions like these were finally answered (for example "how come light seems to appear in discrete packets?"), the answer ended up being a door to a completely new understanding of reality, and not a little footnote question at the End of Physics So yeah, when there are no more unanswered physics questions, I will consider that the laws of physics have been exhausted. Right now that's not the case.

snek_case 5y ago

You also have to realize that the Kardashev scale [0] is something invented by someone in 1964. It's more a science fiction idea than some law of nature. We can't take for granted that this is some natural progression for every technological civilization. > it just makes sense to only needing to build the facilities to collect the power from existing sources (stars, black holes) without the logistics of transporting the fuel. Yeah OK, but then you have to transport your entire reactor to the fuel. For that matter, you also have to transport the energy where it's needed once you've harnessed it. [0] https://en.wikipedia.org/wiki/Kardashev_scale https://en.wikipedia.org/wiki/Kardashev_scale

PaulHoule 5y ago

The counter is that most of the usable mass in the universe is in interstellar objects such as comets and free planets which are 50% water ice or so, rich in organic materials and can be consumed completely to build habitats. With D + D fusion (easy to believe compared to CNO) an interstellar civilization could be essentially independent of stars. I'm sure part of the resolution of the Fermi paradox is that dry inside-the-frost-line planets like Mercury, Venus, Earth and Mars are not the generic places you find life. If things were a bit different I could see a would-be Galileo on an less cooked version of Io or a more cooked version of Europa who looks at the Earth with a spectroscope and sees oxygen and has a huge amount of trouble with his local "church" that thinks it is impossible to have life on a planet with less tidal activity, less radiation, inside-the-frost-line dryness, etc. Even if creatures like us became interstellar we might have millions of kilometers of condominiums and shopping malls in the oort cloud and could care less about inner solar system planets.

SkyMarshal 5y ago

Any idea if there’s enough construction material in any given planetary system to construct a Dyson sphere around its star? Seems like it would require, at minimum, several planets worth of raw material.

serverholic 5y ago
In reality you probably wouldn't see a dyson sphere but a dyson swarm instead. With that you just need millions of thin sheets of material to reflect energy.
- TremendousJudge 5y ago
  >In reality Why do people keep insisting on the Dyson concept as though it was real, even though it's just the fanciest thing we can imagine with our current understanding of physics? The same way in the 19th century nuclear power couldn't be envisioned, there's definitiely a bunch of technology we don't know about now that an alien civilization could be using; we could even be observing this right now and we would be none the wiser. Talking about Dyson shperes, or swarms, or rings, and then concluding that there's now alien civilzations because we can't see them is just anthropocentrism, failing to consider other possiblities
  - JohnJamesRambo 5y ago
    It’s possible this is as advanced as we can get. Innovation seems to be slowing down don’t you think? At some point you have exhausted the laws of physics and this is what you’ve got to work with. https://www.cold-takes.com/this-cant-go-on/ https://www.cold-takes.com/this-cant-go-on/
    - TremendousJudge 5y ago
      It's possible, but I find it extremely unlikely. The "end of physics" has been predicted several times, even in the face of obvious unanswered questions, like today's "what's the deal with dark matter and dark energy?", "can chaotic processes be understood?", "what even _is_ gravity?" When in the past, unanswered, mystery questions like these were finally answered (for example "how come light seems to appear in discrete packets?"), the answer ended up being a door to a completely new understanding of reality, and not a little footnote question at the End of Physics So yeah, when there are no more unanswered physics questions, I will consider that the laws of physics have been exhausted. Right now that's not the case.