[extropy-chat] sjbrain calcs

[Robert J. Bradbury]

On Sun, 21 Dec 2003, Spike wrote:

> If we had an SJBrain, the space in
> which the Jupiter mass of nodes resides is much smaller
> than the space occupied by a true Jupiter-MBrain, half a
> cubic light minute

Either I still don't understand this picture Spike or there is
something wrong with your calculations or Anders.

Anders' Jupiter Brain (Zeus) has a radius of ~9000 km (~1.5
Earth masses) and mass of ~10^25 kg (~1.8 Earth masses).
Its probably going to require much of the carbon (for diamondoid)
that is in the inner planets, the Oort cloud and a good chunk
of Uranus, Neptune and some of the larger moons.  If he makes
the communication fibers out of silicon he may not have enough
Si in the solar system without star lifting.  On top of that
since he wants to run it at 4K he is going to need a good
amount of helium from the gas giants as well.

> as opposed to Robert's 250,000 cubic light minutes.
> The notion of collision control in an SJBrain
> is more difficult.

You must be pulling these numbers out of the air spike.  I don't
think I ever specified the size of an MBrain.  If my calc's are
right 250,000 culm gives you a radius of 39 light-minutes which is around
the asteroid belt someplace.  Actually if you can avoid the people
on Earth screaming you start building an MBrain way inside the
orbit of Mercury using TiC as the primary material.  As you
dismantle the asteroids and planets (smallest first) it continues
to grow an increasing number of outer layers out of lower temperature
nanomaterials to build the very outermost layers you probably need
quantities of material from multiple brown dwarfs (or have star-lifted
it out of the sun) and you end up with a diameter of several light-years.

Robert