I wonder about that thing. I’ve heard, unofficially, that they’ve detected about 30 similar signals from elsewhere in the sky, but like the first, they were never repeated.

The WOW signal was about four milliseconds long and patterned at the microsecond level. My first thought when I heard that was, “4,096 bits.” Are we picking up data packets sent by alien computers or space probes? If so, it would tend to confirm that the speed of light limit is absolute and that there’s nothing better than radio to be discovered, so I sincerely hope it turns out to be some natural phenomenon.

http://www.bigear.org/CSMO/PDF/CS05/cs05p28.pdf

Scroll down to the section labeled:
B. The Solar System Signature. How Our Solar System Would Appear to an Observer at a Distant Star

There’s a very interesting chart here which shows that humanity’s television broadcasts could be detectible out to 1 light-year. Unfortunately there are no other star systems that close. However our early warning radar signals could be detected at a distance of 100 light-years and our planetary radar signals could be detected out to a distance of almost 10,000 light-years. Of course, these last two signals are very directional so the receiving civilization would have to be by chance in the beam of the signal which is probably not very likely. I wonder if the Wow! signal of 1977 was a similar case, a planetary radar beam sweeping the sky which just happened to interesect Earth.

[[I once read somewhere (Scientific American, maybe) that if there was a civilization just like us around Alpha Centuri, we wouldn’t know about it. Is that true?]]

Quite possibly. Our TV signals get out of the atmosphere and are now quite far away, but they would be extremely faint even by the time they got to Alpha Centauri. Dr. Plait? Could aliens on Alpha Centauri A II pick up the signals from the DEW line or something of the sort? Or would they need an antenna larger than a planet?