The inverse square law of radiation means that only a beam transmission will be received. That beam will have to be pulsed to boost peak power while keeping the average power reasonable. The beam will have to be aimed with an accuracy of a few micro-arcseconds which requires a very large targeting mirror. A blue laser will need a 46-meter diameter mirror polished to the diffraction limit. A red laser will need a 256-meter diameter mirror. This means that whoever is sending the signal must have prior knowledge of an orbiting planet, be capable of anticipating its position, and aiming their beam accordingly in real time. The largest mirrors on earth are the Keck I and II telescopes each with a 10-meter mirror. They are ground based, and subject to atmospheric interference. Our knowledge of extrasolar planets is limited to Jupiter-mass gas giants, we cannot yet image them all directly, and we have only superficial knowledge of their orbits. Therefore we ourselves are not yet capable of sending a signal such as what SETI hopes to find. One might argue that we are not yet capable of detecting it either, if the technology used to transmit is so much more advanced. It may be like trying to examine a microchip with a magnifying glass.... like assuming the message will be in brail, when it is actually a DVD. In these examples not only is the message more densely packed, but it requires fundamentally different technology.

SETI seeks to detect any kind of continuous signal whether beamed or omnidirectional. It is unfathomable why they would expect anything less sophisticated than a beamed signal, which means the Drake equation should have a new parameter: the probability that a beam transmission is aimed at us, rather than another star. This is on the order of 1 chance in a billion.

SETI' s only virtue is that their methods are thorough. Therefore it will still be a scientific result even if they detect nothing. If they detect nothing, it could mean that humans are not yet an intelligent species compared to what is out there.

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