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Which is why they are also thinking about signals like neutrinos and gravity waves (which are much harder to produce but much better suited to interstellar dist

by yodon 9y ago

Which is why they are also thinking about signals like neutrinos and gravity waves (which are much harder to produce but much better suited to interstellar distances). While it's never possible to say "everything has been discovered/invented" we know a great deal about the types of particles and waves that can exist at realistic energy levels for use in communication systems because those energy scales have been so well studied. The odds that there is "new physics" to be discovered at a scale that will supplant radio waves for broadcast communications on a terrestrial scale are pretty low.

jerf 9y ago
"neutrinos and gravity waves (which are much harder to produce but much better suited to interstellar distances)." No, they aren't. Both are freakishly difficult to detect, and we have no reason at this point to expect that to ever change. And gravity waves are actually terrible for interstellar distances because it is completely unclear how you would produce a source of gravity waves powerful enough to transmit across interstellar distances, and also transmit in a beam. If you can't transmit in a beam, you're stuck with very unfavorable dropoffs as distance increases. It is also unclear why, having built the utterly massive complexes for transmission or detection of gravity waves, or the massive complexes required for high-probability neutrino reception (transmission in their case is a bit simpler, though collimating the beam is rough) it would not simply be easier to use electromagnetic waves, which are by comparison so easy that if we had a receiver in another star system we could transmit to them today. Barring some major revelation in physics, aliens will use electromagnetic waves because everything else is literally (and I mean that in its original correct sense) dozens of orders of magnitude worse. Smart aliens do not demonstrate how much smarter they are than us by using engineering solutions dozens of orders magnitude inferior to what we could build today. However, as my previous text implies and as other commenters have already pointed out, the problem there is that efficiency is obtained at that scale with beams, not broad transmission. The galaxy could be hopping with point-to-point links and they would be much harder for us to notice. (They wouldn't be impossible, because there would be some scattering on the interstellar medium. But they'd be much more difficult than if we were directly the target.)
- yodon 9y ago
  We're in agreement that gravity waves and neutrinos are harder to produce and detect. They are better for long interstellar distance communications because their weakly interacting nature and difficult to produce nature means there is no dispersion relationship to worry about, no absorbtion/attenuation issues to worry about, and no noise sources to worry about. The galaxy is a surprisingly difficult medium to send radio waves through if you want them to be received at great distances (difficult medium, not impossible medium). That's one of the things that led early SETI thinkers like Barney Oliver to propose using the spectral Water Hole[0] as a search target. Gravity waves and neutrinos are harder to produce and detect but the galaxy itself is much less likely to interfere with their propagation if you can produce and detect them. Also, communications uses of gravity waves would presumably be at much higher frequencies so the detector sizes would be much smaller (the size of an interferometer or Weber bar detector is a function of the center detection frequency of the device... sensitivity is largely independent of the size, other than the choice of center detection frequency). [0] https://en.wikipedia.org/wiki/Water_hole_(radio) https://en.wikipedia.org/wiki/Water_hole_(radio)

by yodon 9y ago

jerf 9y ago

"neutrinos and gravity waves (which are much harder to produce but much better suited to interstellar distances)." No, they aren't. Both are freakishly difficult to detect, and we have no reason at this point to expect that to ever change. And gravity waves are actually terrible for interstellar distances because it is completely unclear how you would produce a source of gravity waves powerful enough to transmit across interstellar distances, and also transmit in a beam. If you can't transmit in a beam, you're stuck with very unfavorable dropoffs as distance increases. It is also unclear why, having built the utterly massive complexes for transmission or detection of gravity waves, or the massive complexes required for high-probability neutrino reception (transmission in their case is a bit simpler, though collimating the beam is rough) it would not simply be easier to use electromagnetic waves, which are by comparison so easy that if we had a receiver in another star system we could transmit to them today. Barring some major revelation in physics, aliens will use electromagnetic waves because everything else is literally (and I mean that in its original correct sense) dozens of orders of magnitude worse. Smart aliens do not demonstrate how much smarter they are than us by using engineering solutions dozens of orders magnitude inferior to what we could build today. However, as my previous text implies and as other commenters have already pointed out, the problem there is that efficiency is obtained at that scale with beams, not broad transmission. The galaxy could be hopping with point-to-point links and they would be much harder for us to notice. (They wouldn't be impossible, because there would be some scattering on the interstellar medium. But they'd be much more difficult than if we were directly the target.)

yodon 9y ago
We're in agreement that gravity waves and neutrinos are harder to produce and detect. They are better for long interstellar distance communications because their weakly interacting nature and difficult to produce nature means there is no dispersion relationship to worry about, no absorbtion/attenuation issues to worry about, and no noise sources to worry about. The galaxy is a surprisingly difficult medium to send radio waves through if you want them to be received at great distances (difficult medium, not impossible medium). That's one of the things that led early SETI thinkers like Barney Oliver to propose using the spectral Water Hole[0] as a search target. Gravity waves and neutrinos are harder to produce and detect but the galaxy itself is much less likely to interfere with their propagation if you can produce and detect them. Also, communications uses of gravity waves would presumably be at much higher frequencies so the detector sizes would be much smaller (the size of an interferometer or Weber bar detector is a function of the center detection frequency of the device... sensitivity is largely independent of the size, other than the choice of center detection frequency). [0] https://en.wikipedia.org/wiki/Water_hole_(radio) https://en.wikipedia.org/wiki/Water_hole_(radio)