Robert Harris wrote:

Also, do you think that in time, signals will be more tightly
compressed and better targetted, to allow more more selectivity, and
using less power?
The satellite signals you mentioned, are meant for large audiences.
Undoubtedly, they will be replaced by methods which permit on demand,
selectivity. I just wonder if the kind of individually-targeted signals that we
will eventually employ, will be too weak to be heard across stellar
distances.
Or to put it another way, as civilizations optimize their techologies,
won't they use only minimal quantities of power to transmit
information?

If there are ETIs out there and if they span more than one planet or more than one star system, then high speed communication might be important to them and those technologies might use a scatter approach.

Or for a local version, if the moon is colonized and you would like to send ads or radio shows to all of the moon, then a scatter approach would work fine.  Yes, minimal power might be advantageous, but it seems technology goes through many ups and downs in efficiencies.  At some points technology is finely tuned and compressed and efficient and at other times, it is scattered and uncompressed.

geothermal