[AR] Re: Freeman Dyson, RIP
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 10 Mar 2020 16:55:06 -0400
On Tue, Mar 10, 2020 at 04:19:18PM -0400, Henry Spencer wrote:
On Tue, 10 Mar 2020, Norman Yarvin wrote:
...the message will get through eventually. If the
outer layers get hotter and hotter, eventually the outward heat flow will
start to slow, and the core temperature will start to rise.
Still, the core temperature of the sun is millions of degrees.
Raising the surface temperature by a mere thousand degrees would have
a hard time changing it significantly.
If you've enclosed the whole thing in a mostly-reflective sphere, it's not
going to stop with a mere thousand degrees. Given time, temperatures
inside the sphere will rise until either radiant heat emitted outward by
the sphere equals energy generation inside, or something breaks (e.g. the
sphere starts to melt and disintegrates).
I'd bet on the manmade thing (or even the men themselves) breaking
before the sun did. Why would anyone try to be that thorough, though?
Leave out half the area, and a thousand degrees is about right for the
temperature rise. (T^4 scaling, and a starting temperature of 6000 K)
For that matter, a reflective sail doesn't have to point the radiation
directly back at the sun; it can miss it by a bit and get hardly any
loss of thrust. Indeed, it's probably easier to miss than to hit.
That won't work with a complete sphere, but could reduce the impact
from covering half the sphere to nearly zero.
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