Saturday, December 18, 2010

A window on the Drake equation

Frank Drake's famous equation for the number of detectable civilizations is based on one seriously flawed idea. That a civilization wants to be detected.

This is not a given and there may be all sorts of reasons for this. A planet populated by a prey species may have a serious problem with advertizing their presence, for example.
Thre may also be another factor, that of the digital revolution. We have discovered that analogue signal transmission is horribly wasteful of overcrowded electromagnetic radiation bandwidth. As a result, we have moved relatively swiftly towards low power, digital transmissions. Our massive radio and television transmission arials are becoming rarer as we switch to digital signals. The off planet transmission of high power signals are slowly being phased out, not because we want to hide but because analogue signals are too expensive to transmit and totally unneccessary.
In this case, the case of Earth, the high power transmission phase will last for about a hundred years. We began pumping the airwaves full of high power signals in the 1930's and it will have stopped well before 2030. Other civilizations may have made the digital leap earlier on and so will not need a high power analogue transmission phase.
This means that civilizations which have surpassed the analogue transmission phase that bleeds vast amounts of signal into space, will have to take a positive decision to transmit something visible over great distance.
Ten thousand detectable civilizations may be reduced to a half dozen who are stupid enough to advertise their positions through the use of low frequency, high power analogue signals.

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