[ExI] The Great Silence again

[Anders Sandberg]

A square meter at distance r from the sun will receive L/4 pi r^2 Watts 
of sunlight. If it re-radiates that as a blackbody we get the relation 
sigma epsilon T^4 = L/4 pi r^2 (where sigma is 5.6e-8 and epsilon is the 
emissivity). Rearranging we get

T = [L / 4 pi sigma epsilon r^2]^0.25

For epsilon 1, r = 149e9 (1 AU) and L=3.83e26 W we get the temperature 
409 K, or 136 C. It is a fun exercise to adapt this analysis to a sphere 
half in shadow and see what "natural" temperature Earth would have.


Henrique Moraes Machado (CI) wrote:
> <Stefano Vaj>
> I have always wondered, however, if such a sphere built by the
> re-arrangement of the non-stellar matter of our system would find its
> internal surface at a distance from the sun suitable to life... I have
> no idea, also because I expect that the internal temperature of a
> Dyson star would probably be fairly different from that of a planetary
> surface at the same distance...
> </Stefano Vaj>
>
>
> It would probably be as hot as Venus. I don't know how to really 
> calculate it and I'm merely speculating based on the fact that the day 
> in Venus is 243 Earth days long. Sunlight 24/7 square angle can do 
> nasty things. Yes, I know about Venus atmosphere and such.
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-- 
Anders Sandberg,
Future of Humanity Institute 
James Martin 21st Century School 
Philosophy Faculty 
Oxford University