> I don't believe they can find different solutions unless they find
> different laws of physics.
We don't know the laws of physics. We know what we know. We have inferred rules from experimental data which is often unverifiable. We hope that our ideas are close (many are, but many still need to be tried and tested by implementing technologies using such science - this is particularly true of astrophysics - it's all theory.) but they are almost definitely not spot on.
Secondly, and more importantly (this is central to my argument) you cannot say from what persepective an alien intelligence might view the universe. We look up at night and see absence of photons, speckled with photon sources, because we detect photons. But what about things we don't detect, things we have not yet discovered, or have misunderstood. These things will represent the differences between civilisations. For all you know the universe could be saturated with "slorgopo energy" which many creatures detect for some purpose or another, but we don't, it has no observable effect upon our systems and so we haven't noticed it, and evolution hasn't utilised it. Perhaps this slorgopo energy is very useful for many technological applications (like radio). There could be civilisations sweeping the galaxy for slorgopo sources, confidently associating this energy with intelligent life, because their neighbouring civilisations use it too. This situation would be much more valid than the one we're in......at least these aliens have some examples upon which to make their assumption. We have none, yet sweeping assumptions of great similarity are still made. "How else would they do it?" as if we know everything, is simply not good enough.
> > 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
> *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.
This is irrelevant. It doesn't make the assumption that similarly advanced alien civilisations use radio any more valid.
> > 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").
None of this means jack until we have more alien tech info (i.e more than none). These are issues which come into play considering exactly our human level of understanding and technology. They probably won't apply elsewhere with great frequency.
> > 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.
Aaaaaagh! How would they have been detected? Do we have a "life-scan" that we can use on other planets from here? NO! This all started by my saying that you can't be SURE that similarly advanced alien civilisations are using radio - AND pointing their transmitters our way, therefore, such a civilisation could easily be at the nearest star, and we wouldn't know. It all rests on the assumption that they're ALL going to use radio and try to contact us, or accidentally transmit to us for some other reason - a ridiculous assumption IMHO.
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