[ExI] Computronium planet.

[Anders Sandberg]

On 12/10/2012 08:35, Keith Henson wrote:
> The radiators would depend on what they were doing. Used for fairly 
> slow access, a planetary scale device might not need to much cooling.

Yes, but even a tiny energy usage per cubic meter would get hot fast. A 
sphere with radius R producing P Watts per cubic meter will need to get 
rid of 4 pi R^3 P/3 Watts. It can radiate from the surface, 4 pi R^2 
epsilon sigma T^4 Watts. That gives an equilibrium temperature of [R P/3 
epsilon sigma]^(1/4). So if R=6e6 meters,  P=1e-6 W/m^3 the temperature 
will be around 100 K. For a milliwatt it will be 570 K - good for 
cooking. A Jupiter-sized version would be just as hot with a microwatt 
performance.



>   It would be an interesting place, dark, faint spill of light around 
> the sun blocker, land areas covered with rectennas, fast uploaded 
> civilization in the depths heating the the oceans to steaming, 
> freezing cold rain falling everywhere, vast rivers running off bare 
> rock continents. Inside the simulation conditions could be as nice as 
> anyone wanted, but the underlying reality would be stark, worse than 
> Mordor. Be hard to detect though, since the shading disk would 
> probably be circular.

Sysop Sauron was watching the cooling indicators of Mount Doom. "We are 
seeing a spike in server latency, what the heck are those heavens doing?"
"They are apparently running a cross-civilization marathon game. Should 
be over soon when the NPCs have evolved sentience."


-- 
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University