In the movie Contact, the action starts with the Very Large Array, a large radio telescope in the U.S., picking up an alien radio signal.

This approach is typical of our current attempts to detect alien intelligences. We assume they will use radio messages to announce their presence, basically because that is what we would do.

Problems with this approach include having the need to have the antennas pointed in the right direction at the right time and having the radio receiver tuned to the right frequency.

Things are improving. Radio telescopes in operation or under construction can see larger and larger areas of sky, can monitor many frequencies at once and moreover, the search for alien signals can be piggy-backed on other experiments, making more observing time available.

Finally, we have to recognize the signal as artificial. This depends on how the information is imprinted on the radio transmission. Without knowing that, the signals might just sound like receiver noise or the hiss from the Milky Way.

So, can we assume our alien........

© Castanet