Seth Shostak of SETI has said that an alien civilization could setup a telescope in an orbit beyond the equivalent of Pluto, using their star's gravitational le

Seth Shostak of SETI has said that an alien civilization could setup a telescope in an orbit beyond the equivalent of Pluto, using their star's gravitational lensing to detect any Earth electronic activity up to a thousand light years away. Of course they would have to wait on our signals to reach that far out first.