Re: Twinkle, Twinkle Little Star, How I Wonder Where You Are (Forwarded)

From: Alfred A. Aburto Jr. (aburto_at_sbcglobal.net)
Date: 08/05/04 

Date: Thu, 05 Aug 2004 12:53:12 GMT

Still, I'm not particularly clear how negative index of refraction occurs in
space?

>"Andrew Yee" <ayee@nova.astro.utoronto.ca> wrote in message
news:dAgQc.35619$Vm1.786884@news20.bellglobal.com...
> University Relations
> Pennsylvania State University
>
> Contacts:
> A'ndrea Elyse Messer, (814) 865-9481, aem1@psu.edu
> Vicki Fong, (814) 865-9481, vfong@psu.edu
>
> August 4, 2004
>
> Twinkle, Twinkle Little Star, How I Wonder Where You Are
>
> University Park, Pa. -- Whether viewed dimly through the haze and lights
of a
> city or in all their glory in a pristine wilderness, the stars that
surround the
> Earth are magnificent, and one day Earthlings will travel to some of the
new
> planets that astronomers are locating. However, the stars we see are not
> necessarily where we think they are, according to an international
research team.
>
> "We know that the light from distant stars takes a very long time to reach
the
> Earth," says Dr. Akhlesh Lakhtakia, distinguished professor of engineering
> science and mechanics, Penn State. "But, taking into account the distance
a star
> will have moved while that light travels, we still may not be able to
accurately
> locate the star."
>
> Negative phase velocity media or materials with negative refractive index
may be
> responsible for this locational uncertainty. Recently, materials
researchers at
> the University of California San Diego, working with micro and nano
materials,
> developed a metamaterial that had a negative refractive index for
microwaves,
> proving that negative phase materials could exist at least in the
microwave part
> of the electromagnetic spectrum. Their requirements for this material were
that
> both the relative permittivity, a measure of the charge separation in a
> material, and the relative permeability, a measure of how electrons loop
in
> materials, of a substance must be less than zero.
>
> While the implications for negative phase velocity media in the nano world
are
> the creation of a perfect lens, a lens with no distortion with
applications for
> optical transmission devices, CDs, DVDs, microwave systems, etc., in the
> universe at large, these media can disguise the location of a star,
according to
> the researchers.
>
> A material with negative index of refraction transmits light or other wave
> energy differently than one with positive index of refraction. In all
natural
> materials, when an energy beam -- light, radar, microwave -- passes
through
> water or glass or some other material, the beam is displaced in the same
> direction. The amount of displacement depends upon how much the material
slows
> the speed of the beam. In negative phase velocity media, the displacement
is in
> the opposite direction.
>
> Lakhtakia and Tom. G. Mackay, lecturer in Mathematics, University of
Edinburgh
> decided to look at why the permittivity and permeability had to be less
than
> zero. They found that one or both permeability and permittivity could be
less
> than zero and negative phase velocity would occur. They then found that
both
> could be greater than zero and a negative index of refraction would occur
but
> only when special relativity came into play.
>
> The researchers looked at transmission through space, where high
velocities are
> common.
>
> "First I did the derivations with the observer moving and the energy
source
> stationary," says Lakhtakia. " Then Mackay did the derivations with the
observer
> stationary and the light source moving."
>
> What they found was that it depends on the state of the observer whether
any
> particular media at any time has negative or positive index of refraction.
The
> relative velocity of the observer changes the index of any material.
>
> "Light coming off a stellar object passes through many different regions
of
> space filled with different media and is affected by different
gravitational
> fields," says Lakhtakia. "When we finally see it, we cannot really know
where it
> originated."
>
> While this may be of no consequence today, Lakhtakia believes it has
important
> implications for when space travel is common. Because this is a direction
> dependent effect, it will change the telemetry of objects and spacecraft.
>
> "The business of space navigation and interpreting star maps could be a
lot more
> complicated than we now think it is," says Lakhtakia. "Imagine mining of
> extrasolar asteroids. We might not want to send humans to do the mining,
but
> robots would have to know where the asteroid is and where on its surface
to mine
> when it left our solar system."
>
> Calculations would need to be made from Earth on an asteroid that might
not be
> where we visually see it. The effects of negative phase velocity media
would
> need to be taken into consideration.
>
> Another problem would be navigating from somewhere far away from the Earth
in a
> space ship using information gathered from the Earth. Depending on the
velocity
> of the spacecraft and the object aimed for, negative phase velocity media
> between the spacecraft and the destination would also need to be
considered.
>
> **aem**
>
> EDITORS: Dr. Lakhtakia is at 814-863-4319 or akhlesh@psu.edu by email.

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  • Re: Twinkle, Twinkle Little Star, How I Wonder Where You Are (Forwarded)
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