The Earth is gradually vanishing from the view of any aliens that might be looking for us, because we are using fewer technologies that leak radio waves into space.
This is the view of one of the pioneers of the SETI project, Frank Drake. (SETI stands for Search for Extra Terrestrial Intelligence, in case you just crash landed.)
His remarks cast doubt over the current search methods employed by SETI in their hunt for little green men, but, he says, also suggest a reason for the deafening silence out there.
According to New Scientist our transition from radio tranmissions to cable TV could mean that our window of detectability is no more than 100 years.
In the 1960's Drake developed an equation that gave researchers a ball park figure of how many planets in the galaxy are home to intelligent, communicating species.
One of the factors in the equation is the longevity of the observable communications, now, Drake says, this is substantially reduced. Assuming any hypothetical Aliens have developed at a similar pace to ours, and accounting for the fact that we're looking for a needle in a haystack in the first place, we shouldn't be too disheartened that we've not found anyone out there. Yet.
So instead of trying to eavesdrop on unintentional signals, we should be searching for beacons: signals sent to us deliberately. In fact, SETI has begun to do just this, but the activity is very new. ®