How many times a day do we send out signals that can reach other Solar Systems?

• Trying to figure out if we sent one hail-mary signal aimed at the globular star cluster M13 some 25,000 light years away (Arecibo message http://en.wikipedia.org/wiki/Arecibo_message) or have we been sending signals to the closer solar systems like: 1. Proxima Centauri - Distance: 4.2 LY 2.Rigil Kentaurus - Distance: 4.3 LY 3. Barnard's Star - Distance: 5.9 LY 4. Wolf 359 - Distance: 7.7 LY 5. Lalande 21185 - Distance: 8.26 LY FYI: Everyday Radio and TV Signal can only be detected about 0.3LY do to the fact that there not Narrow done. Website: http://en.wikipedia.org/wiki/Fermi_paradox#Communication_is_impossible_for_technical_reasons The greatest problem is the sheer size of the radio search needed to look for signals (effectively spanning the entire visible universe), the limited amount of resources committed to SETI, and the sensitivity of modern instruments. SETI estimates, for instance, that with a radio telescope as sensitive as the Arecibo Observatory, Earth's television and radio broadcasts would only be detectable at distances up to 0.3 light years.[61] Clearly detecting an Earth type civilization at great distances is difficult. A signal is much easier to detect if the signal energy is focused in either a narrow range of frequencies (Narrowband transmissions), and/or directed at a specific part of the sky. Such signals can be detected at ranges of hundreds to tens of thousands of light-years dis

• Answer:

  First, I have an allergy for misuse of terms. 'Solar' (system) pertains to our Sun and there is only one "SUN", others are called "Stars", just as I can't be called "Scotty" just because I have a pair each of legs, eyes, ears and whatever else like "Scotty" (that is you) has. You may call others as planetary systems of a particular star (planetary system of Proxima Centauri). You are referring to a Communications problem related to Astronomy. One ought to talk to an Electronics & Communications Engineer or consult any one of ten thousand text books on the subject by Jasik, Jordan or Ramo. An Antenna array (Arecibo has one) typically operates in a very narrow band. It is particularly so since one needs to concentrate on a single frequency (that' d be ideal but not practical), say 21cm wavelength. If you want it to be broadband spread over bandwidth wide enough and higher power proportionately pumped in. Inverse square law reduces this power to a trifle when it goes through Space. I would have a power of at least a few MW into the antenna to reach a better part of a LY (1 LY=63115 AU; 0.3 LY=18934.5 AU) if not 1 LY. Radio transmission of energy is OK, but humanity it appears is greedy to receive signals with information content. How much justified are we in assuming that that intelligent civilisation that we target is like us. They read and can write, understand graphics on plane sheet (nobody asks the question do they have eyes like us working in visible part of spectrum), conversant with radio. They should even read one of our languages; may be English. Ridiculous isn't it? Underlying assumptions of SETI (& CETI before) need a reapprisal lest the whole exercise becomes a shot in the dark. It raises the expectations needlessly high provoking the uninitiated into painting a picture of visitors to our planet and so on, to popularise an urban cult of 'aliens' and such legends.