Shostak misses the point

[qraal]

Seth Shostak's latest thoughts on extra-terrestrial messaging via slow probe kind of misses the point - that aliens don't have to send just one probe in vain hopes of it being found. If they can make one they can make millions and send them to every habitable star system in the galaxy - and that would still be cheaper than signalling via radio. Seth's not a radio-bigot who can't see past a radio telescope and has written on the value of space-probes himself, but surely the advantages of communicative probes sent to alien star systems and able to communicate in real time makes sense?<br />Interesting he noted that the economy of beaming signals can be improved by using solar energy, but misses the equal value of solar energy to space-probes. Using a plasma magnet to capture the solar wind a space-probe can reach ~ 300 - 900 km/s and then deccelerate at the target star-system. This improves the efficiency of the system out of sight compared to radio - firstly because a plasma-magnet sail gets a ~ 1000-fold enhancement out of the power it uses by using the solar-wind as its propulsion, and secondly because it means no fuel is needed at the target system.<br />Alternatively the probe can be launched via solar-pumped lasers pushing a solar-sail - conceivably a probe could reach ~ 0.1c [merely ten times slower than radio] and use a plasma sail to deccelerate for virtually no fuel expenditure at the destination and "free" solar power for launch. Solar energy cuts both ways - and hence probes are still cheaper.

 

[qraal]

One final point - probes can wait indefinitely to be found, but ETIs need to be lucky to look in the right part of the sky to pick up a radio signal.

 

[bobvanx]

You could also reasonably expect an advanced civilization to be sending out messaging von Neuman machines, so that the galaxy is chock-full of messages...<br /><br />Oh wait, that's sort of like panspermia.<br /><br />Life itself is the message.