# [ExI] matrioshka brains again

Ben Zaiboc ben at zaiboc.net
Mon Apr 24 13:08:46 UTC 2023

```On 24/04/2023 05:16, Lason Resch wrote:
> I think we can calculate what the temperature of the ring would be at
> 1 AU using the Stefan-Boltzmann Law
> <http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c1>.
> Incident solar radiation at 1 AU is 1360 W/m^2. In order to reach an
> equilibrium temperature, the ring needs to radiate 1360 W to stop
> increasing in temperature. According to the Stefan-Boltzmann Law, we
> need to solve for T in this equation: 2*(5.7603*10^-8)*(T^4) = 1360,
> note I use 2 here because the ring has two sides to radiate from, one
> facing the sun and one facing away from the sun.

If I may chip in, isn't all this assuming that each node will absorb,
and then must cope with all the incident radiation?
My question would be, why not reflect away what's not needed? A variable
or adjustable reflector could only allow into the node as much energy as
was required. Seems pointless to absorb radiation that you just need to
get rid of again.

We wrap spacecraft in silver foil to stop them overheading, why not
Matrioshka Brains?

Ben
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