RE: "Web-mediated SETI": Robert Bradbury Replies

Robert J. Bradbury (
Fri, 5 Nov 1999 20:09:18 -0800 (PST)

I'm going to respond to Billy's note and then suggest a temporary "hold" on this discussion because it seems needed.

Robin and others have raised good points and to put them all in perspective I need to present a coherent rationale on the other side. I don't know if I will be able to prepare that soon since this month I'm in Moscow and am in business plan writing mode, but it is on my todo list.

On Thu, 4 Nov 1999, Billy Brown wrote:

> When I do this kind of theorizing I start with a lifeless universe, and try
> to work forward to a theory that explains the present without as few
> unsupported assumptions as possible. I see that there is no particularly
> convincing evidence that there is anyone out there, so I think "well, there
> must not be anyone out there".

But this could easily be an assumption similar to those we had before the invention of the microscope. Before that, we couldn't "see" bacteria we had no theories about their existence!

> When some SETI enthusiast brings up the Drake equation I merely note that
> a list of unknowns does not constitute evidence - we know essentially
> nothing about how easy it is for intelligent life to evolve, and we
> therefore can not expect to predict anything from such an analysis.

I want to stress that I don't start with the assumptions in the Drake equation. I start with the problems I have with physicists making up new particles (MACHOS) to explain the observed galaxy masses.

> Robert, OTOH, seems to start by presuming that the universe must be filled
> with sentient life.

I put my making up "intelligence populating the universe" as being on equal footing with the physicists making up MACHOS, except mine at least has an existing concrete example of 1, while theirs requires has no concrete examples [both require a lot of theoretical hand waving].

> [snip] He searches the universe of possible SI behaviors for
> some set, however implausible, that might give that result, and then treats
> that set of assumptions as if it were the simplest possible explanation for
> observed facts.

Actually, I try to limit "behavioral" choices to those that are *highly* rational (driven by the physical laws and optimal solutions to problems). If we can define those, then we probably have the "simplest" explanation.

> This leads to some remarkably pointless debates.

I don't find them useless, they help me refine the points I need to make to have people consider alternate explanations.

> ... requires you to make a whole raft of assumptions about the
> nature of SI civilizations, and ask for evidence that these assumptions are
> correct.

It is true, the only way this thing can hold together is if I can limit the assumptions to those that rationally make sense. The environmental niches and evolutionary histories of SI-ETC may be so complex however that simple explanations may become very complex. If so the natural history of SI-ETC is going to be as difficult to comprehend as modern physics.

> So, why don't we start at the beginning. I look around our corner of the
> universe, and see that I can explain all of my observations quite well
> without invoking extraterrestrial intelligence.

But you can't explain "all of the observations". I've got 5+ astronomical "observational problems" that do not have good explanations. Right now of the only problem I see in astronomy that may get a believable solution in the near future is the cosmic ray bursts (blazars, etc.). The arguments there seem to be holding up without inventing new physics, cosmological constants, etc.

> Why, then, should I add in
> the complicating assumption that there must be SIs out there somewhere?

Because you have two problems you have got to solve: (a) the lack of aforementioned explanations for astronomical observations. (b) the really thorny problem of "We are alone".

      [We *are* on the SI evolutionary path.  You have a lot of explaning to
       to do if we are *unique* in 200+ billion stars in 200+ billion galaxies.]

IMO, the weight of (*b*) is *so* strong that even if you had completely consistent non-magical explanations for what you observe that you had better not trust them too much unless they can *explain* completely the process by which (b) occurs. [As things are now, people use the observations to assume (b), but that doesn't explain *why* its true.]

If I'm interpreting the other posts correctly, Hal seems to have settled, perhaps uncomfortably, on at least the possibility of having to not completely disregard possible "miracles", while Eliezer seems to allow them but figures its by and large irrelevant.

Slowly, gentle-Is, step by step, we will move as Max says, Onward. As Eliezer pointed out, the truth doesn't really care.