atdtda: 31 - pg 871

[Bekah]

Omg.    What's next - or do I really want to know?

Bekah


On Apr 27, 2008, at 7:39 AM, kelber at mindspring.com wrote:

> http://www.livescience.com/technology/061019_invisibility_cloak.html
>
> "Scientists have created a cloaking device that can reroute certain  
> wavelengths of light, forcing them around objects like water  
> flowing around boulders in a stream. To creatures or machines that  
> see only in microwave light, the cloaked object would appear nearly  
> invisible."
>
> Laura
>
> -----Original Message-----
>> From: Bekah <Bekah0176 at sbcglobal.net>
>
>
>> 871:37   "Cyprian recited the appropriate formulæ and  became
>> invisible."
>>
>> From The Invisible Man by H.G. Wells  (1897) - Chapter 19  (the
>> formula for invisibility concerns refraction and light):
>>
>> "But I went to work -- like a slave. And I had hardly worked and
>> thought about the matter six months before light came through one of
>> the meshes suddenly -- blindingly! I found a general principle of
>> pigments and refraction, -- a formula, a geometrical expression
>> involving four dimensions. Fools, common men, even common
>> mathematicians, do not know anything of what some general expression
>> may mean to the student of molecular physics. In the books -- the
>> books that Tramp has hidden -- there are marvels, miracles! But this
>> was not a method, it was an idea, that might lead to a method by
>> which it would be possible, without changing any other property of
>> matter, -- except, in some instances, colours, -- to lower the
>> refractive index of a substance, solid or liquid, to that of air --
>> so far as all practical purposes are concerned.
>>
>>
>> Phew!" said Kemp. "That's odd! But still I don't see quite -- I can
>> understand that thereby you could spoil a valuable stone, but
>> personal invisibility is a far cry."
>>
>> "Precisely," said Griffin. "But consider: Visibility depends on the
>> action of the visible bodies on light. Either a body absorbs light,
>> or it reflects or refracts it, or does all these things. If it
>> neither reflects nor refracts nor absorbs light, it cannot of itself
>> be visible. You see an opaque red box, for instance, because the
>> colour absorbs some of the light and reflects the rest, all the red
>> part of the light, to you. If it did not absorb any particular part
>> of the light, but reflected in all, then it would be a shining white
>> box. Silver! A diamond box would neither absorb much of the light nor
>> reflect much from the general surface, but just here and there where
>> the surfaces were favourable the light would be reflected and
>> refracted, so that you would get a brilliant appearance of flashing
>> reflections and translucencies, -- a sort of skeleton of light. A
>> glass box would not be so brilliant, not so clearly visible, as a
>> diamond box, because there would be less refraction and reflection.
>> See that? From certain points of view you would see quite clearly
>> through it. Some kinds of glass would be more visible than others, a
>> box of flint glass would be brighter than a box of ordinary window
>> glass. A box of very thin common glass would be hard to see in a bad
>> light, because it would absorb hardly any light and refract and
>> reflect very little. And if you put a sheet of common white glass in
>> water, still more if you put it in some denser liquid than water, it
>> would vanish almost altogether, because light passing from water to
>> glass is only slightly refracted or reflected or indeed affected in
>> any way. It is almost as invisible as a jet of coal gas or hydrogen
>> is in air. And for precisely the same reason!"
>>
>> "Yes," said Kemp, "that is pretty plain sailing."
>>
>> "And here is another fact you will know to be true. If a sheet of
>> glass is smashed, Kemp, and beaten into a powder, it becomes much
>> more visible while it is in the air; it becomes at last an opaque
>> white powder. This is because the powdering multiplies the surfaces
>> of the glass at which refraction and reflection occur. In the sheet
>> of glass there are only two surfaces; in the powder the light is
>> reflected or refracted by each grain it passes through, and very
>> little gets right through the powder. But if the white powdered glass
>> is put into water, it forthwith vanishes. The powdered glass and
>> water have much the same refractive index; that is, the light
>> undergoes very little refraction or reflection in passing from one to
>> the other.
>>
>> "You make the glass invisible by putting it into a liquid of nearly
>> the same refractive index; a transparent thing becomes invisible if
>> it is put in any medium of almost the same refractive index. And it
>> you will consider only a second, you will see also that the powder of
>> glass might be made to vanish in air, if its refractive index could
>> be made the same as that of air; for then there would be no
>> refraction or reflection as the light passed from glass to air."
>>
>> "Yes, yes," said Kemp. "But a man's not powdered glass!"
>>
>> "No," said Griffin. "He's more transparent!"
>>
>> "Nonsense!"
>>
>> "That from a doctor! How one forgets! Have you already forgotten your
>> physics, in ten years? Just think of all the things that are
>> transparent and seem not to be so. Paper, for instance, is made up of
>> transparent fibres, and it is white and opaque only for the same
>> reason that a powder of glass is white and opaque. Oil white paper,
>> fill up the interstices between the particles with oil so that there
>> is no longer refraction or reflection except at the surfaces, and it
>> becomes as transparent as glass. And not only paper, but cotton
>> fibre, linen fibre, wool fibre, woody fibre, and bone, Kemp, flesh,
>> Kemp, hair, Kemp, nails and nerves, Kemp, in fact the whole fabric of
>> a man except the red of his blood and the black pigment of hair, are
>> all made up of transparent, colourless tissue. So little suffices to
>> make us visible one to the other. For the most part the fibres of a
>> living creature are no more opaque than water."
>>
>> http://www.readprint.com/chapter-10225/H-G--Wells
>>
>> But Cyprian is in Venice thinking these things and waiting for Theign
>> to show up.
>>
>> Bekah
>>
>
>

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