archiv~1: Re: SETI Arecibo message to m13

Re: SETI Arecibo message to m13

Alfred A. Aburto Jr. ( (no email) )
Thu, 05 Nov 1998 21:52:15 -0800

Yes of course lasers can be used to communicate in such a manner
as (perhaps) to be very difficult to detect unless it was pointed
right at you. But consider this ...

Some day (I think, I know there alot of other options, but I think
we'll make it) humans will occupy the entire Solar System. There
will be great commerce throughout the Solar System. Shipping lanes
and high traffic areas and congestion! Communications (low to very
high power from perhaps millions of sources) will be beamed from
Earth to Pluto and beyond. The human population of the Solar System
may be measured in the 100's of trillions! High powered lasers will
be used all over the place. Radio waves and communications and
video will be transmitted with much more power as much greater
distances will need to be covered (not just across Earth as today,
but across the Solar System). Think of not just one laser beam but
perhaps thousands or millions!

This kind of energy usage by us (an advanced technological
civilization) should be easily detectable. I'm saying we should have
already noticed something from civilizations of this type or greater!
But, instead, not even the slightest clue has popped up. I'm just
pointing out a puzzling fact (the Fermi Paradox really) ...

A friend of mine says, perhaps we will not be able to grow into huge
populations into the 100's of trillions because perhaps the scarcity
of trace elements like iodine will naturally limit growth (set
natural thresholds that we will not be able to overcome).

It may be true too that maybe we just have not looked carefully
enough yet, or with enough sensivity or resolution yet ...

Al

> David Woolley wrote:
>
> > we as a civilization will be vast users of energy. We would
> > be easily noticed elsewhere (outside the Solar System)
> > communicating across the Solar System using terrawatts or
> > more of power (we use kilowatts to megawatts to communicate
>
> Ignoring for the moment the problems of even 5 year technology forecasts,
> it seems to me that it would be reasonable to use lasers to communicate
> with such colonies, in which case there may well not be much overspill
> of directed power, and the power that didn't overspill would be scattered
> and, to some extent, degraded by absorption and re-radiation as heat.
>
> The high gain of a laser transmitter would reduce the total power needed
> for a given bit rate.
>
> > around the Earth today but 1000 years from now when the whole
> > Solar System is our base it will be gigawatts and terrawatts).
>
> Even if large total powers were used, even todays technology would
> tend to either spread the spectrum or use large numbers of channels.
> Argus detection strategies depend on all the power being in one channel,
> and I suspect, even Chip's theories require a lot more structure
> in the signal than would result from commercial optimisation of the
> interplanetary links.