SETI Microprobes and Interstellar Travel

Richard Burke-Ward (
Wed, 8 Sep 99 17:03:49 +0100

Dear all,

First up, where is everybody? Is it just me that is getting maybe one
posting from this list every other day, or has the list just gone quiet?
I suspect I'm badly behind the times, because I only ever got David
Woolley's reply to Allen Tough's reply to something or other on the above
issue, but none of the original messages... So if I am repeating
something, then do forgive.

Interstellar microprobes need not travel unprotected at even
sub-relativistic speeds. How about if they hitch rides with comets? It
would be the interstellar equivalent of Tarzan swinging from tree to
tree. Get a ride to the outskirts of system A, jump to a comet on the
outskirts of system B, nudge it out of the belt and into the system, drop
a few probes in system B as you pass through, then jump ship in favour of
a comet which can take you into system C... It may not get you to every
solar system in the galaxy, but it would get you to a lot of them. Nice
and slow, nice and protected, with an almost limitless source of raw
materials for self-replication / sub-probe creation.

David, I know you were not arguing interstellar microprobes were
impossible, just that there were technical challenges involved. This is
true. However, I think arguments such as yours are too often seen by
others as 'proof' that probes are impossible. So it is worth just setting
out again some of the reasoning.

Probes might be self-replicating, or launched as a fleet. Either way,
let's be miserably pessimistic and say that it would take a wave of
probes 100 million years to saturate the galaxy. That is 100th the age of
our galaxy. I truly find it hard to imagine that, in roughly 10 billion
years, with a few hundred billion stars to choose from, that no single
instance of intelligent life has had such an idea and at least partially
implemented it. (OK, let's assume you need second generation stars, plus
intelligent life takes 4 billion years to evolve - so make that 4 billion
years.) It follows that there is at least a chance we could find evidence
of extraterrestrial intelligence *within the confines of our solar

Arguments against looking for such evidence seem weak. There are the
technical ones - we don't know interstellar travel is possible, etc.
Well, NASA seems to think it is - even with technology only a hundred
years or so beyond present day - plus we've had at least one meteorite
land on Earth which originated in another solar system - plus we are
talking about ETI's with technologies considerably in advance of our own.
Interstellar travel is probably difficult (so is space flight, so is
building a computer) - but to rule out interstellar travel as impossible
when we cannot possibly *know* it is impossible seems very foolish. The
other argument against looking for probes in our solar system really
comes down to ignoring the problem and hoping it will go away - 'give us
a good search stgrategy and maybe we'll think about it...' Several people
have been offering good ideas for years - Allen Tough among them. And
more to the point, if people don't like the ideas that have been
suggested, why not *help* us design good ideas? The important thing is to
recognise the *need*.

I personally find it haunting in the extreme to think that I may be
sitting within a few AU of absolute proof that ETI exists. It may not be
a functioning probe, it may just be a relic - even the equivalent of a
flag planted millions of years ago... If someone told you that there was
a 50% chance that something like AC Clarke's obelisk really *was* sitting
on the moon (or in orbit, or on an asteroid), would you just ignore the
possibility? Effectively, that's what's happening. That chance is very
real indeed - and no one seems to want to do a thing about it.

This isn't cranky. This is an attempt to define a new branch of SETI. One
with a real chance of success.

Not everyone can do everything. The SETI League is a radio-based
organisation. But its members are not solely interested in radio, they
are also interested in ETI. Plus they (you all) are deeply creative,
innovative, and have the courage to think new thoughts. If any new
initiative in the area of searching for probes were to start, the grass
roots of the SETI League would be a wonderful place for it to happen.

If anyone is interested in throwing ideas around, I would love to talk
with you. I know Allen - and a few others - would too. You might also
want to have a look at a mathematical treatment of the problem on my
website - I try to quantify the chances that there is something here
worth looking for - (some of you have already
looked and commented - thanks).


This archive was generated by hypermail 2.0b3 on Sun Oct 10 1999 - 15:46:34 PDT