Re: SETSIs (fwd)

Robert J. Bradbury (
Wed, 28 Jul 1999 09:55:00 -0700 (PDT)

> John Clark <> wrote:

> Robert J. Bradbury <>

>For the record, Sullivan et al (Science 199:377-388 (1978)) showed that: > An Arecibo-size antenna could detect UFH TV out to 2 light-years

> And the Arecibo antenna could detect transmissions from another Arecibo size
> antenna anywhere in the galaxy if it were aimed at the Earth yet we find no
> such message.

Do you have a source for this? [I'm not doubting this, I just want the hard data.]

> The theory that ET is deliberately hiding from us is no theory at all
> because is not provable. if they don't want us to find them we haven't
> a snowball's chance in hell of doing so, besides I don't see why they'd
> think we were worth all that effort. The reason is probably the simplest,
> we can't detect ET's because they don't exist.

There are enough "unexplained phenomena" (i.e. missing mass, gravitational microlensing observations, excess infrared radiation in nearby galaxies, missing "stars" according to standard stellar evolution theories, gamma ray "glows", etc.) that one can reasonably postulate that *they do exist* if one reconciles existing observations with evolution to the limits of known physics. The hiding vs. observable discussion revolves around the fundamental question of whether you are willing to risk "detection" (and therefore attack) tradeoff with intelligence (and defense capabilities).

If intelligence/local defense wins over remote attack capabilities then all SIs should be "observable". If there is a tradeoff between defense & intelligence/observability then there may be "stealth" SIs.

The fact that "they aren't here" or "they aren't easily observable" are easily explained by the advantage of "local optimization of capacities". Remote activities don't gain you very much once you are at the SI level.