4 ms·

So we are another kind of special to deserve observation and galaxy wide bubble of silence.

• philipkglass 8y ago
  No, I'm assuming that probes are widely distributed. Laser communication is better than radio communication over long distances. Shorter wavelengths make for tighter beams. The whole galaxy could be mesh-networked with ultraviolet laser links and repeaters, and it would still take a rare stroke of luck for any of our telescopes to notice, even if the links aren't operated for deliberate stealthiness.
  • red75prime 8y ago
    Tight laser beams are limited by diffraction. Kilometer wide laser beam on wave length 308mn will have diameter around 15 millions meters on 4 light year distance. Meter wide beam will have diameter 15 billions meters, all other things being equal. I can't, right now, estimate probability of breaking the silence, though.
    • philipkglass 8y ago
      Right, a 15 billion meter wide beam aimed at e.g. a solar gravitational lens relay station some 542 AU out, or even aimed at much closer receiving stations around Jupiter, would not intersect Earth most of the time. At 308 nm it wouldn't be visible to ground based telescope since the atmosphere would mostly absorb it. If using gravitational lensing to set up system-to-system communication is the norm, the beam might not be bright enough to be observable by current space based UV telescopes. All of this could just be driven by ordinary post-biological-alien good engineering practices. It would seem extremely stealthy to humans, but that doesn't need to be intentional, any more than ham radio communications are intentionally stealthy against observation by whales.