archiv~1: Re: SETI Arecibo message to m13

Re: SETI Arecibo message to m13

David Woolley ( david@djwhome.demon.co.uk )
Wed, 4 Nov 1998 08:14:23 +0000 (GMT)

> 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.