Re: SETI/ASTRO: MBrains/JBrains & Globular Clusters

From: Robin Hanson (
Date: Wed Jul 18 2001 - 07:55:24 MDT

Robert Bradbury wrote:
> > ...might be worth following the argument through to see
> > what velocity it suggests.
>Hal did a rough cut on that (Thanks Hal). The 6 small
>objects would appear to be going ~40x faster than the
>larger object. The orbital speeds in our solar system
>range from 4.7 km/sec for pluto to 47 km/sec for Mercury. ...

I think perhaps I explained myself badly. I meant doing
a theoretical analysis. For example, consider a brain
floating between the stars. If the point of moving around
is to every once in a while come close to some other brain
to exchange info, then there should be a tradeoff regarding
speed of motion. The faster you go the more often you get
to exchange info. But the faster you go the more energy it
might take to manage your trajectory, or to protect yourself
against collisions.

>One other reason has occured to me for fast transit times.
>If JBrains are star-lifting by direct encounter, e.g.
>fast transit through the star's upper atmosphere sucking
>up material as you go, then I suspect you are going to
>want those orbits to be made at fairly high velocity.

That sounds like another place where we could estimate
the optimal speed.

Here is the key point. It seems to me unlikely that the optimal
speed for these purposes will turn out to be near the current
typical speeds of planets or stars. So if we find out the
speeds of these things are indeed near typical other speeds,
that would seem to be a strike against your theory.

>Stellar velocities span at least an order
>of magnitude (so J/MBrains could potentially start with
>a range of velocities almost as large), it isn't clear how much
>value such a velocity prediction would have.

But I suspect the theoretically optimal speeds for various
purposes will span many orders of magnitudes.

Robin Hanson
Asst. Prof. Economics, George Mason University
MSN 1D3, Carow Hall, Fairfax VA 22030-4444
703-993-2326 FAX: 703-993-2323

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