|MadSci Network: Astronomy|
Well, that depends how hard they are trying. We have the _technology_ to detect radio emissions at power levels similar to those we employ in broadcasting (a few megawatts equivalent isotropic radiated power, EIRP) but we do not have the _money_ available yet to mount a search for such tranmissions at this high a sensitivity. There are a few SETI systems currently in use, but with more modest sensitivity. Indeed, even as I write this note I am observing a nearby star with the most sensitive of these systems, as part of Project Phoenix. We can detect transmitters that have EIRP's of a few gigawatts. While that sounds awfully large, it is not all that much for highly directional transmitters. For example, I am using the 140 foot telescope of the National Radio Astronomy Observatory in Green Bank, West Virginia. If there were a similar antenna near the star I am looking at, it would only need a transmitter of a few tens of kilowatts to make a signal I could detect. Many of our more powerful radars and atmospheric research systems transmit with powers of more than a few GW. So, while our current search is not as sensitive as we'd like, we still have some (unknowable) chance of detecting other civilizations, either from broadcasts more powerful than we currently use (solar-system-wide broadcasting, power satellites, terraforming...??) or because they are trying to get our attention with a directed signal. We are, needless to say, thinking about how to build systems of much greater sensitivity with a budget that we could have at least some hope of obtaining. Unfortunately, one of the biggest potential sources of SETI funding, the federal government, no longer sponsors any SETI work, because a senator from Nevada doesn't like it. Fortunately, there are many private individuals who do, and who donate money and/or materials to support the efforts of the various SETI groups. You can find more about Project Phoenix, as well as links to other SETI efforts, such as SERENDIP and BETA, on the web pages of the SETI Institute at: http://www.seti-inst.edu
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