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

From: Andrew Yee (ayee_at_nova.astro.utoronto.ca)
Date: 08/05/04 

Date: Wed, 04 Aug 2004 22:03:58 -0400

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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