4 ms·

Would be true for omnidirectional transmission. Much much less for a directed transmission.

• henryfjordan 7y ago
  You'd have to know where the aliens are for that to matter!
  • erik_seaberg 7y ago
    Hitting a fixed target, from light-years away, with a signal stronger than cosmic background? Pretty sure a world-class team could get PhDs just for the attempt.
  • dredmorbius 7y ago
    Given the detection of exoplanets of approximately Earth mass orbiting in habitable zones, that's rapidly become tenable. Laser / maser signalling would probably be about the best we could do for now.