6 ms·

Complete tangent of course, but I wonder if aliens using laser communication methods might be why we aren't being bathed in radio waves.

by sosuke 12y ago

ekianjo 12y ago
Radio waves go in multiple directions, lasers can only work in short range, unless you find a superb trick to keep the alignment perfect at great distances.
- talmand 12y ago
  Simple, you just keep tapping it with a rubber hammer until you get alignment.
- sylvinus 12y ago
  I don't know if you need a "trick"... Just several orders of magnitude more precision?
  - ekianjo 12y ago
    Yeah, and just like for telescopes, when you need several orders of magnitude more precision, you need something huge to do so. Unless we find a way to build huge spaceships in space, it's not coming anytime soon.
- lutorm 12y ago
  Actually, I think this is less of a problem than you think. Lasers have significant divergence, see for example the Marcy paper an astro-ph that was referenced elsewhere in this thread. Telescopes can already track targets at the diffraction limit, so it's no different to send a laser. What is different is that you have to know the relative proper motion of the target, since you have to "lead" the target just like you do when skeet shooting. I don't know whether the lead angle is significant, but proper motions of nearby stars have been measured (e.g. by Hipparcos http://en.wikipedia.org/wiki/Hipparcos http://en.wikipedia.org/wiki/Hipparcos) and calculating the resulting lead angle isn't difficult.
ceejayoz 12y ago
That's one of the proposed solutions to the Fermi Paradox. Human TV signals are already dying out as they get supplanted by cable/fiber, and what's left like cell phones is constantly being engineered to use less power.
- talmand 12y ago
  Maybe the falloff in output has convinced them our civilization is dying and not worth contacting.
  - daeken 12y ago
    Considering that our radio waves haven't traveled very far, I doubt this is true. Remember, a planet 60 light years away is just now hearing Elvis for the first time.
    - talmand 12y ago
      The ships hiding on the dark side of the moon have heard everything...
- johnchristopher 12y ago
  That seems unlikely to me. Why wouldn't at least a few alien civilisation keep broadcasting radio signals just to let others know they are there too ?
  - justinpombrio 12y ago
    Not for very long. http://xkcd.com/1377/ http://xkcd.com/1377/
  - ceejayoz 12y ago
    Maybe there a much better ways of doing so that we discover in another couple decades? Who knows.

Complete tangent of course, but I wonder if aliens using laser communication methods might be why we aren't being bathed in radio waves.

by sosuke 12y ago

Complete tangent of course, but I wonder if aliens using laser communication methods might be why we aren't being bathed in radio waves.

ekianjo 12y ago

Radio waves go in multiple directions, lasers can only work in short range, unless you find a superb trick to keep the alignment perfect at great distances.

talmand 12y ago
Simple, you just keep tapping it with a rubber hammer until you get alignment.
sylvinus 12y ago
I don't know if you need a "trick"... Just several orders of magnitude more precision?
- ekianjo 12y ago
  Yeah, and just like for telescopes, when you need several orders of magnitude more precision, you need something huge to do so. Unless we find a way to build huge spaceships in space, it's not coming anytime soon.
lutorm 12y ago
Actually, I think this is less of a problem than you think. Lasers have significant divergence, see for example the Marcy paper an astro-ph that was referenced elsewhere in this thread. Telescopes can already track targets at the diffraction limit, so it's no different to send a laser. What is different is that you have to know the relative proper motion of the target, since you have to "lead" the target just like you do when skeet shooting. I don't know whether the lead angle is significant, but proper motions of nearby stars have been measured (e.g. by Hipparcos http://en.wikipedia.org/wiki/Hipparcos http://en.wikipedia.org/wiki/Hipparcos) and calculating the resulting lead angle isn't difficult.

ceejayoz 12y ago

That's one of the proposed solutions to the Fermi Paradox. Human TV signals are already dying out as they get supplanted by cable/fiber, and what's left like cell phones is constantly being engineered to use less power.

talmand 12y ago
Maybe the falloff in output has convinced them our civilization is dying and not worth contacting.
- daeken 12y ago
  Considering that our radio waves haven't traveled very far, I doubt this is true. Remember, a planet 60 light years away is just now hearing Elvis for the first time.
  - talmand 12y ago
    The ships hiding on the dark side of the moon have heard everything...
johnchristopher 12y ago
That seems unlikely to me. Why wouldn't at least a few alien civilisation keep broadcasting radio signals just to let others know they are there too ?
- justinpombrio 12y ago
  Not for very long. http://xkcd.com/1377/ http://xkcd.com/1377/
- ceejayoz 12y ago
  Maybe there a much better ways of doing so that we discover in another couple decades? Who knows.