SCIENCE & TECHNOLOGY

Invisibility cloak
S.S. Verma

We are fascinated when have an opportunity to read in books or see in sci-fiction movies about a character that can make himself invisible or undetectable to common people and work for the benefit of mankind. Scientists and engineers are working to explore the optics of invisibility.

Water beyond solar system?
Evidence of water has been detected for the first time in a planet outside our solar system, an astronomer said on Tuesday, a tantalising find for scientists eager to know whether life exists beyond Earth. Travis Barman, an astronomer at Lowell Observatory in Flagstaff, Arizona, said water vapour has been found in the atmosphere of a large, Jupiter-like gaseous planet located 150 light years from Earth in the constellation Pegasus.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE
PROF YASH PAL
How was the work done in the space shuttle Columbia helpful in the treatment of cancer? I am asking this because such a claim was made.

 


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Invisibility cloak
S.S. Verma

We are fascinated when have an opportunity to read in books or see in sci-fiction movies about a character that can make himself invisible or undetectable to common people and work for the benefit of mankind. Scientists and engineers are working to explore the optics of invisibility.

Cloaking technology (called electronic mask) is always seen at work on television, when blue backgrounds are used to make a person invisible on the screen. This technology (optical cloaking) is used to make Romulan spaceships disappear in Star Trek science fiction.

Electronic and optical cloaking are, however, different. In optical cloaking the object becomes invisible to visible light wavelengths. Though the object will be there but we will not be able to see it (object).

Objects are visible in the optical range because they reflect light, a process also called scattering. Objects absorb light, too, and what is absorbed is not seen. The sky is blue because the atmosphere scatters blue light more than red. If the object absorbs all the light falling on it, it will be a black object and if it reflects all light wavelengths it will be a white object.

However, if the reflected light wavelengths from the object can be cancelled by other radiations or the object transmits all the light wavelengths as such then the object can appear invisible to the eyes just like vacuum.

Though reflection, absorption and transmission of light are the fundamental properties of any object but these phenomena can be controlled by taking into account the refractive index and wavelengths/frequencies of waves refracted by the object. Scientists are trying to control these optical phenomena and are able to observe optical cloaking.

Though it will take a long time to make the whole object and variety of objects invisible but a humble version of the device could become a reality, according to researchers. Nader Engheta and Andrea Alu of the University of Pennsylvania indicate that high-tech cloaking machines could one day render very small objects nearly invisible.

But don’t expect to hide yourself or your spaceship anytime soon, at least not in the standard sense of invisible. In practical terms, the research is more likely to lead to improved technical and research devices, and even these applications are years away.

Back in 1998, researchers led by Thomas Ebbesen of the Louis Pasteur University in Strasbourg, France shone light on a sheet of gold foil that contained millions of tiny holes. The holes were smaller than the wavelength of the light, and Ebbesen expected no light to get through. Amazingly, more light came out the other side than what hit the holes. Follow-up research found that plasmons — quanta of energy flowing in the plasma waves on the surface of the metal — were snagging light and stuffing it through the holes. Plasmons are real, a product of a strange characteristic of light, which is made up of both particles and waves. Plasmons are created when electrons on the surface of a metallic material move in rhythm.

They have other odd properties. When the energy and momentum of the photons match the energy and momentum of the plasmons, the photons are absorbed and radiated again on the other side.

The proposal of Engheta and Alu involves using such plasmons to cancel out the visible light or other radiation coming from an object. Alů and Engheta’s plasmonic screen suppresses scattering by resonating in tune with the illuminating light. A proper design may induce a dramatic drop in the scattering cross-section, making the object nearly invisible to an observer.

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Water beyond solar system?

Evidence of water has been detected for the first time in a planet outside our solar system, an astronomer said on Tuesday, a tantalising find for scientists eager to know whether life exists beyond Earth. Travis Barman, an astronomer at Lowell Observatory in Flagstaff, Arizona, said water vapour has been found in the atmosphere of a large, Jupiter-like gaseous planet located 150 light years from Earth in the constellation Pegasus. The planet is known as HD 209458b.

Other scientists reported in February that they were unable to find evidence of water in this planet’s atmosphere, as well as another Jupiter-like planet.

“I’m very confident,” Barman said in an interview. “It’s definitely good news because water has been predicted to be present in the atmosphere of this planet and many of the other ones for some time.”

Lowell Observatory, a privately owned astronomical research institution, announced the finding, which has been accepted for publication in the Astrophysical Journal. The research was backed by NASA, it said. The detection of the presence of water vapour was possible because this planet, from the vantage point of Earth, orbits directly in front of its star every 3-1/2 days, allowing crucial measurements to be made. It is what is known as a transiting planet. — Reuter

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THIS UNIVERSE
PROF YASH PAL

How was the work done in the space shuttle Columbia helpful in the treatment of cancer? I am asking this because such a claim was made.

I do not know the exact answer, nor am I sure that there is some special magic of working out in space. Maybe what I have just said is not quite correct because the weightless environment of space does offer the possibility of doing chemistry and biochemistry where the effect of convection is almost completely eliminated.

This might allow the possibility of some reactions proceeding with greater ease without the effect of mass differentiation. For a problem like cancer one would try anything.

It is true that in space environment of micro-gravity one can grow very large perfect crystals. Several other material science experiments have also been done.

One of the techniques of estimating the masses distribution of large protein molecules is to measure the distance they travel in a gel under the influence of an electric field - heavier the molecule slower is its motion. This technique is called electrophoresis. It is clear that this method would work better under conditions where differentiation due to gravitational settling is eliminated.

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