The digital television revolution means that Earth is less likely to be discovered by aliens, according to an expert.

Frank Drake told a Search for Extra-Terrestrial Intelligence workshop at Harvard that "the Earth is going to disappear" very soon for aliens.


He says radio signals put out by traditional television broadcast antennas are the strongest evidence of our existence in space, reports New Scientist.

Traditional antennas put out one megawatt each and this radio-wave bubble now extends about 50 light years out from the solar system.

But more and more television is now delivered by cable, with no radio-frequency leakage to space, and by satellites that put out just 20 watts per channel, all efficiently directed straight down to Earth.

However, Drake said it might also explain why we have so far failed to uncover any evidence of aliens - if other forms of life have followed the same technological path.