> > Rob Harris Cen-IT <Rob.Harris@bournemouth.gov.uk> wrote:
> I'm talking about the probablility of dissimilar entities choosing an
> identical solution to us for the communication problem.
I don't believe they can find different solutions unless they find different laws of physics.
> The EM communication paradigm may well represent a VERY insignificant
> vector in a VERY large solution space. (note the MAY)
I agree (simply from a philisophical viewpoint) -- I want my warp drive now.
*However*, from a practical viewpoint of what we spend our time and/or hard earned dollars/pounds/yen etc. on it makes a fair amount of sense to stick with "known" physics.
> Of course I accept the possibility of others using radio etc, but,
> given the efficacy range (given the time loss) of radio detection
> and the possible plethora of alternatives,
Ah, but if you look at the simple physics of Shannon's law,
carrier bandwidths, propagation of the signal through space and
the amount of information an advanced civilization would have
to communicate, you can come up with a "reasonable" strategy
that would universally minimize costs and maximize communication
(given known laws) --
(1) Focus on building telescopes first to identify planets where
life might exist [observation costs less than transmission]. (2) Transmit a directed radio signal to these planets on one
of the logical frequencies (there are a number of them proposed by Cocconi & Morrison, Kardashev, etc. that are based on universal physical constants and minimum interference in space, so at the destination they have a high S/N ratio. The message should only say one thing -- "switch to 488 nm" (argon laser) (or some other high frequency optical signal). Given the delays involved you don't want to make this signal "hard to find" by making it a very narrow bandwidth (which is what all that SETI@home data is). (3) Wait for a response at that frequency, and then do a massive data dump on the high bandwidth carrier.
The idea of ping-pong-ing signals back over light-years on a low-bandwidth carrier makes no sense at all. Now it may be that you skip step (2) entirely because you only want to communicate with people who have the technology at level 3 (i.e. big space-based laser-"grids").
> I don't think it's likely SETI will come up trumps - even if a
> similarly advanced civilisation exists at the nearest star.
Well if they were at the nearest star there is a good chance they would have been detected by now -- we have been at this for 40 years. Most of the sun-class stars within a 10-20 l.y. distance have been studied quite a bit. I believe the SETI Inst. has a list of the studies which have been made.