Earth has changed technology and shifted from using leaky radio signals and broadcasting radios to fiber optics and short range wireless. If aliens followed our pattern then SETI is analogous to a system of detecting teenagers who have their music set to a volume of eleven. When you do not find teenagers with megaspeakers blasting that does not mean there is no life within detection range, but just no noisy teenagers.
The Square Kilometre Array (SKA) will operate in frequency ranges often used by military radar and other communications technology. It has been shown that if Extraterrestrial Intelligences (ETIs) communicate using similar technology, then the SKA should be able to detect such transmissions up to distances of 100 parsecs (300 light years) from Earth. However, Mankind has greatly improved its communications technology over the last century, dramatically reducing signal leakage and making the Earth “radio quiet”. If ETIs follow the same pattern as the human race, will we be able to detect their signal leakage before they become radio quiet? We investigate this question using Monte Carlo Realisation techniques to simulate the growth and evolution of intelligent life in the Galaxy. We show that if civilisations are “human” in nature (i.e. they are only “radio loud” for 100 years, and can only detect each other with an SKA-like instrument out to 100 pc, within a maximum communication time of 100 years), then the probability for such civilisations accidentally detecting each other is low ( one in ten million chance), much lower than if other, dedicated communication techniques are permissible (e.g. optical SETI or neutrino communication).
These results are based on an assumed observation duration of 1 month. If we extend this to 10 years, then the SKA’s detection radius extends to 1000 pc.
The conclusions of this paper are not new, and it has been appreciated for some time that the discovery of radiation from civilisations at our present-day level and with short timescales would be unlikely. Our work simply updates these arguments using the latest predictions for the possible distribution of planets harboring life in our Galaxy, and the probable sensitivities of the newest radio arrays. Such a conclusion could also be seen as being rather pessimistic for SETI but like others, we would like to stress that we are guaranteed to find nothing if we give up looking. What these results stress strongly is that SETI must be a multi-wavelength endeavour, conducted with broader horizons (Davies, 2010) and a better understanding of our own limitations.