Re: Cloaking devices??

>Me:
}Steve:

>Active EMS or EMS Jammers as a cloaking device.  Well, sorry to get
>back to it so late, but I just thought you might wanna know that this
>is (of course) impossible.

}Hmmm... then why is GM talking about using it on cars in 1994?

GM has Active EMS?  Wow!  TL 10 sensors in TL 6 cars!

}I also seem to recall seeing a news article on test operations in use
}today.  It didn't work real well with anything but low frequency
}stuff, but it did work.

This is all sound stuff.  By producing a destructive interferance pattern
in a confined box, (the muffler) it greatly reduces noise.

>There is an analogous short story by Arthur C. Clarke called
>"Silence, Please."  Which appears in "Tales From the White Hart"

}Yes, I've read it.  Written in the late 40s-early 50s, right?  Before
}computers?

Correct, but computers won't solve the problem as presented there.

>In order to create such an interferance pattern, one would have to
>know, the exact position of the listener (to within a wavelength of
>the sound in question) as well as how they were moving to take
>doppler shift into account.  Now you might be able to do that for ONE
>observer, but if the observer moved, even slightly, the effect would
>be lost.

}No.  If it out of phase here, it will still be so there, assuming that
}the signal is an exact copy of the incoming.  And if you match the
}wavelength incident where you are, the doppler shift will shift it
}right along with the original signal you are trying to mask.

Ok, Light comes in and is reflected off the hull.  In order to be able to
destructively interfere with that reflection, you will have to know not only
the freqency of that light, but its polarization as well.  If you can't get
the polarization correct you won't be able to interfere with it at all.
Sunlight is randomly polarized.  There is no way to get it to match something
that is totally random.  But let's say for the moment that you do know the
polarization and the freqency.

You then pick up and measure each and every freqency of light coming in and
send it back out out of phase.  Now, observer A is travelling alongside the
ship at the same speed.  Observer B is approaching at some speed.  The ship
emmits light and disappears from view of observer A.  Observer B, however
sees the light that is reflected at it's normal freqency and the light that
is emmitted by the ship with it's freqency doppler shifted.  Thus, Observer A
can't see the ship, but Observer B can.

}I don't believe that 3000 years additional research
}won't be able to come up with a better result.

It can with nice long wavelengths and an unpolarized vibration like sound,
but not with light.

>Now, to attempt this with light, you might be able to fool one
>observer, BUT you would have to know their EXACT position.  To within
>a wavelength of light, ie down to nanometer acurracy.

}Nonsense.  Are you suggesting that I have to know your exact position
}for you to SEE me?  If you can see me, then I can flash a light in
}your eyes.  And if the light were just so, then you wouldn't see me
}any more.  If you assume (and you have so far) that the sensor arrays
}are all over the hull, then you could get a pretty good copy by
}generating a counter-signal at each point on the array to match
}incident EM at that point.  It won't be perfect, by any means (unless
}technology improves in 3500 years - a long shot, some people think),
}but it will be better than letting them see you without even trying to
}hide.

You still have the problem of polarization.


}And you can monkey with neutrino
}sensors by EMMasking your ship, but not your drone, or by using a
}reaction that produces more neutrinos in the drone...

EM (electro magentic) masking takes care of EM radiation.  Not nuclear
radiation.  It will do absolutely nothing to neutrino emmissions.  And
as far as I know, neutrinos are only emmitted in certain nuclear reactions.
(fusion, and fission I believe)  Those would certainly be the easiest way
to get a source of neutrinos.  And fusion/fission plants are expensive.


}And I never suggested a cloaking device.  Hans inferred that.  I was
}suggesting something to make you ship HARDER to detect, not
}impossible.

Well, using the above technology might allow you to reduce your signature
somewhat, at least in terms of the amount of light your ship emmits.  You'd
have to make certain all the freqencies and polarizations of your ship were
matched by your cloaking emmitters.  But it *might* be able to reduce your
emmitted signature.  It won't work against incident light, but maybe.
But then again, this sounds exactly like what the EMMasking is supposed to be
able to do.

Maybe what you've been describing is the EMMask not EMS-Jam.  We never have
had *any* explanation as to how EM Masking is supposed to work.

Scott Kellogg