Expert: Jayendra Upadhye - 5/20/2004

Question
Good afternoon, Jayendra

I was wondering how far away we could reasonably expect to detect a civilization (and I use that word loosley!) such as our own - that is, from how far could we pick up 'Get Smart', the 'Doris Day' show and all the other 'stuff' we're constantly transmiting, and have been transmitting for years?
I'm not refering here to detecting a signal that has been specifically 'beamed' at a target star - (would this be much further, do you think?) - but just our 'daily' transmissions.

Cheers, Rod

Answer
Hi,
Rod, That would all depend on how big an antenna and relevent resources the "looker" has invested in!
After all the very very faint signals of the pioneer and voyager aircraft were indeed being recieved well by Nasa from the edge of the solar syatem.
But recieving signals from the true interstellar space (from the heliopause onwards - "where sun's ownership ends and true space begins" - to the average distance to the nearby stars of say 4-5 lightyears is i think currently beyond the reach of our technology.
In order to recieve signals of the type you have mentioned, over such great distances, the source of the signal has to be prodigiously strong and the recieving antenna something like the arecibo antenna.
Carl Sagan mentions a hypothetical formula for finding earth like civilisations in the galaxy.
The formula has a number of factors, one of which is the probability that the civilisation may self destruct in nuclear war or some such self made disaster! Other factors include possibility that the planet is at the right distance from its sun, (not too cold not too hot), has water etc.
Hope that suffices to answer your question.
You will find it in his book named "Cosmos".
Jayen