Re: poly: Malign Probes

Peter C. McCluskey wrote:
>
> hanson@econ.berkeley.edu (Robin Hanson) writes:
> >Before you had hypothesized that life was so dense that aggressive probe
> >reproduction was a bad strategy. This requires not only that each system
> >have some life in it, but that it control most of the resources in that
> >system. Being able to detect and intercept an incoming colonization probe,
> >so that such a probe has an extremely low chance of substantially reproducing,
> >seems incompatible to me to your other hypothesis that life hides under
> >rocks for fear that anything else will be interpreted as an attempt to
> >expand beyond the system.
>
> I've been assuming that detection is more extensive than just probes
> defending their own systems. They are watching several neighboring systems,
> and can at very least detect most objects whose velocity exceeds the
> escape velocity of those systems. I admit I haven't done a rigorous
> analysis of how reliable such detection can be.

Not very reliable for long range sensing. The probes can and should be
accelerator-launched, which makes for little or no signature. Detection
after launch relies mostly (except for easily obviated EMR emissions) on
the interactions of the body with interplanetary and interstellar media,
which creates a wake of sorts.
The effects of banging into dust and atomic particles depend on the
probe's
mass and velocity. A low enough speeds, say less than .01c, these
interactions
pretty well blend into the background (the kineticaly energized
particles
have a mean free path less than the distance to the sensor). Maybe the
interception events themselves could be detected, I'm not so sure.

Whether life needs to
> leave planetary/asteroid surfaces in their natural state, or whether life
> just needs to avoid unnatural emmissions from the system, depends on how
> much more detection from neighboring systems is feasible.
>
> As for interception, I'm assuming that when a system sends out probes,
> one or more neighboring system sends out probes which follow and destroy
> the first set of probes plus the system that sent out those probes.
> I'm not sure whether to assume that the retaliatory probes also attack
> each other or whether they have some way of recognizing each other's
> retaliatory intent.

In this scenario, the probes seem to be identifiable by their
trajectories.
Do recognize that is is very difficult to alter a trajectory in free
space.
It takes as much energy, for instance, to change a velocity vector by 45
degrees as it took to launch the interceptor. Supplying and converting
that energy stealthily is a really tall order.
 
> I think you're implying that such detection systems and retaliatory
> ability need to look conspicuous. I'm assuming that as long as they are
> passively waiting for signs of expansion, they are easy to camoflage.

In a low speed scenario, interceptors, colonization probes and passive
sensors can all be pretty effectively camoflaged as Oort cloud material.

> Setting up such systems undetected is hard, and only succeeds in the
> rare case where life is able to colonize a new system by correctly guessing
> that there are an abnormally low number of malign probes in neighboring
> systems, causing expansion to be safer than normal.

> ------------------------------------------------------------------------
> Peter McCluskey | pcm@rahul.net | Has anyone used http://crit.org
> http://www.rahul.net/pcm | to comment on your web pages?

-- 
Forrest Bishop
Chairman,
Institute of Atomic-Scale Engineering
http://www.speakeasy.org/~forrestb