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Making It Hard For Extraterrestrials To Hear Us
quaith writes "US astronomer Frank Drake has told scientists at a special SETI meeting in London that earthlings are making it less likely that we will be heard in space. In the past, we used huge ground stations to broadcast radio and television signals which could be picked up relatively easily — according to astronomers' calculations anyway. Now we use satellites that transmit at 75 watts and point toward Earth instead of into space. In addition, we've switched to digital which makes the transmissions even fainter. Drake has concluded that very soon, in space no one will hear us at all. I guess we'd better keep listening."
The last factor in the equation is L, the length of time a civilization broadcasts radio waves into space.
We hope your rules and wisdom choke you / Now we are one in everlasting peace
Reading the wikipedia page further, it seems like his understanding of L is that it represented how long a technological society would be capable of broadcasting into space. So it seems like he didn't actually consider that as technology advanced civilizations would significantly reduce the amount of stray emissions. As a result his guess for L was around 10000, a few orders of magnitude off it would seem.
We hope your rules and wisdom choke you / Now we are one in everlasting peace