3 ms·

Except our pockets (unless you wear tinfoil pants) and many other materials are transparent at those wavelengths which makes it a lot less crazy.

• StavrosK 7y ago
  You don't think making an antenna that can detect an LED shining in a flat miles away is crazy because pockets are transparent?
  • swiley 7y ago
    No. Amateur radio operators have done it, and it’s not difficult to imagine how one would.
    • StavrosK 7y ago
      Indeed, nothing is difficult to imagine how to do if the method is common knowledge.
    • burnte 7y ago
      That doesn't make it any less amazing.
  • lolc 7y ago
    In darkness our eyes can easily detect a 1W LED from kilometers away.
    • StavrosK 7y ago
      But can they distinguish a specific 300 mW LED in a stadium with tens of thousands of other LEDs next to it?
      • pcnix 7y ago
        If it were a different color, yes. If each of them were a different color, your eye would still be able to, as long as you had enough focus. So the analogy holds pretty well.
      • swiley 7y ago
        My understanding is that healthy human eyes are able to detect individual photons.