Computing at the speed of light
Radhakrishna Rao
The current genre of computing systems based on silicon chips and electronics circuits are essentially designed for a “rather slow” processing of data. As such, for many years now, researchers have been focusing on an efficient and smart optical system that could speed up the processing function of a computer by a substantial extent.

Primordial comet dust is coming
Deborah Zabarenko
A sample of comet dust, collected by a robotic space probe with what looks a bit like a big tennis racket, is scheduled to parachute down to Earth this month, NASA scientists said.

Trends
Whales speak in dialects
Some whale species sing in different dialects depending on where they’re from, a new study shows. Blue whales off the Pacific Northwest sound different than blue whales in the western Pacific Ocean, and these sound different than those living off Antarctica.

• Elephant tails tell a tale

• Complexity of walking

• Internet use differs

• Harry Potter saves bones

Smart pillows, wardrobes!
“Smart homes” would soon become a reality, involving a set of intelligent home appliances that could understand users’ needs, including old people, those with movement disabilities, low vision, hearing impairment and cognitive impairment, providing them a better home life without overpowering them with complex technology, experts at a seminar here said today.

Prof Yash Pal

Computing at the speed of light
Radhakrishna Rao

The current genre of computing systems based on silicon chips and electronics circuits are essentially designed for a “rather slow” processing of data. As such, for many years now, researchers have been focusing on an efficient and smart optical system that could speed up the processing function of a computer by a substantial extent.

In the ultimate analysis, the goal is to put in place an intelligent machine capable of functioning at the speed of light. Lasers which are already in wide use for carrying large volumes of data over long distances along a fibre optics network are projected as an ideal choice for developing an optical computing system. The most conspicuous advantage of laser is that all the packets of light they generate are of same, uniform wavelength. As it is, to produce a good laser one needs a metal that can take an energy input and turn it into light energy in a regular, rhythmic fashion.

Preliminary demonstration studies under laboratory conditions have shown that a silicon laser can be the best option for building a computer capable of functioning at the speed of light. Indeed, the thrust of current research is on how to engineer a silicon laser good enough to be embedded into the microchips during the process of production.

Clearly and apparently, silicon is the most preferred material for the simple reason that it can be mass produced with ease. However, the most noted drawback associated with silicon is that is what it comes poorly in the task of controlling and managing light. Parallely researchers are also studying materials such as gallium arsenide which is considered efficient in dealing with and controlling light.

Meanwhile, a physicist at the numero uno chip production company Intel based at Santa Clara has claimed that a team led by him has developed a silicon laser that runs without interruption at the normal room temperature. As expected this device produced laser light when it was “pumped” with another laser.

Jerome Faist, a physicist at Neuchatel University in Switzerland has described this breakthrough” as a significant advance towards the development of a “practical silicon laser”.

On the other hand Behram Jalali, the physicist from the University of California at Los Angeles, says that there has been many attempts earlier to develop a workable silicon laser system. But the continuous operation of silicon laser system achieved by the Intel team is a major milestone, says Jalali.

All said and done, many hurdles need to be crossed before a commercially viable and technologically efficient silicon laser system becomes a reality.

In this context Leigh Canham of psi Medica, a British enterprise specialising in research on clinical applications of silicon nano crystals says that “a few years ago people thought that silicon laser was impossible to realise”.

Meanwhile, Lanslet, an Israel based outfit, has claimed that it has developed a computer processor running on an optical system enabling it to compute at the speed of the light. An optical processor is a digital signal processor with an optical accelerator attached to it which helps to perform all the functions at very high speeds. Lanslet points out that “by processing at the speed of the light, one can have safer airports, autonomous military systems, high definition media broadcasting system and an advanced next generation communications systems”.

Primordial comet dust is coming
Deborah Zabarenko

A sample of comet dust, collected by a robotic space probe with what looks a bit like a big tennis racket, is scheduled to parachute down to Earth this month, NASA scientists said.

The spaceship Stardust is coming to the end of its seven-year, 4.8 billion km round-trip mission to fly by comet wild 2, catching dust that could give astronomers clues about how the planets formed some 4.5 billion years ago.

The ship will remain in space but a 101-pound (46 kilogram) capsule loaded with dust culled from the comet is expected to land at the US Air Force Uteh Test and Training Range at 5:12 am EST (1542 hrs IST), or 3:12 am local time on January 15.

“This comet formed at very edge of the solar system... out by Pluto... and spent all its lifetime cut there until recently it came into the inner part of the solar system, where we could sample it,” said Don Brownlee, the principal investigator on the project.

Stardust went halfway to Jupiter to get close to Wild 2, catching hundreds of comet dust particles in a collector that looks something like a large tennis racket with a round metal ice cube tray where the strings would be.

Inside the collector’s ice-cube-size compartments is a material called aerogel, a low-density substance that is 99.9 per cent air, which acted to capture grains of dust emitted by the comet.

Stardust’s collector got within 236 km of Wild 2, close enough to be bombarded by millions of cometary particles, and to catch hundreds of them.

Comets are thought to be the remnants of planet formation, made up of cosmic dust and ice. Comet collisions may have helped seed Earth with water, a prerequisite for life.

NASA officials stressed the Stardust capsule is extremely rugged and said they have prepared for the possibility of a hard landing so the samples will not be damaged before they can be studied.

A previous NASA probe called Genesis crashed to Earth in 2004 when its parachute failed to open. That craft had been on a three-year mission to collect solar ions, which were recovered by scientists even though the spacecraft was destroyed. — Reuters

Trends
Whales speak in dialects

Some whale species sing in different dialects depending on where they’re from, a new study shows. Blue whales off the Pacific Northwest sound different than blue whales in the western Pacific Ocean, and these sound different than those living off Antarctica.

And they all sound different than the blue whales living near Chile.

“The whales in the eastern Pacific have a very low-pitched pulsed sounds, followed by a tone,” said David Mellinger of Oregon State University. “Other populations use different combinations of pulses, tones, and pitches.”

Elephant tails tell a tale

By plucking hairs from elephant tails, scientists have determined just what the pachyderms like to eat.

Researchers combined this dietary information with tracking data from Global Positioning System (GPS) collars to show that an elephant’s diet changes as it migrates.

Different plants produce different ratios of carbon isotopes, which accumulate in an animal’s body-particularly in hair. The isotope ratio of an animal’s hair can therefore reveal what it has consumed.

In tropical regions, trees and shrubs undergo one type of “carbon fixation” during photosynthesis and produce a different ratio of carbon isotopes than grasses and crop plants.

Complexity of walking

Placing your foot down when walking was thought to be a predetermined process: lift foot, decide where to put it based on what’s on the ground, and if nothing moves, land it down on the original target. Scientists thought this procedure requires no immediate visual information once the foot was lifted off the ground.

But a new study has found that continuous visual guidance mechanisms may be needed for accurate foot placement.

“We have demonstrated that vision can be used in an online fashion to fine-tune foot placement during a step,” said Raymond Reynolds, of the Institute of Neurology, Queen Square, London. “It was previously thought that vision was used to plan the step in advance but not necessarily monitor its ongoing progress.”

Internet use differs

Women are now as likely to use the Internet as men — about two-thirds of both genders — yet a new study shows that gaps remain in what each sex does online. American men who go online are more likely than women to check the weather, the news, sports, political and financial information, the Pew Internet and American Life Project has reported. They are also more likely to use the Internet to download music and software and to take a class.

Online women, meanwhile, are bigger users of e-mail, and they are also more likely to go online for religious information and support for health or personal problems. — AP

Harry Potter saves bones

Harry Potter may not yet be able to mend broken bones with a wave of his wand, but the pint-size wizard of book sales apparently has the power to reduce playground injuries, British scientists reported in a study published this week.

Working on a hunch, a group of trauma surgeons from Oxford’s John Radcliff Hospital ran a statistical study on the correlation between the incidence of “musculoskelatal injuries” among 7-to-15 year olds and the release of new volumes in the phenomenally popular Harry Potter series by J.K. Rowling. — AFP

Smart pillows, wardrobes!

“Smart homes” would soon become a reality, involving a set of intelligent home appliances that could understand users’ needs, including old people, those with movement disabilities, low vision, hearing impairment and cognitive impairment, providing them a better home life without overpowering them with complex technology, experts at a seminar here said today.

The Indian Institute of Science, Bangalore, is carrying out efforts to develop “Smart pens” to help people with vocabulary problems by underlining unknown words and pressing a translation key and a “Gate reminder,” which would remind a person leaving for work whether he or she had taken the mobile phone.

“A smart wardrobe digitally looks up weather forecasts for the user so that they can comfortably and adequately coordinate what they wear with the outside environment before they leave the house, while a Smart pillow can select books of choice for reading at bedtime and can play your favourite music to drift off to when you start getting sleepy.

A Smart Refrigerator can help users keep track of individual food items expiry dates as well as manage shopping lists”, he added. — UNI

THIS UNIVERSE
PROF YASH PAL

How do scientists measure or calculate the weight of a planet?

Firstly let me clarify that we do not measure the weight of a heavenly body but only its mass. Your weight changes when you move from the surface of the earth to that of the moon, because the force of gravity changes. Your weight in a space orbit might become zero! But the mass does not change. Your weight is the force of gravity on you and mass is the quantity of matter that determines the inertia you offer when subjected to a force.

It is a deep riddle of nature that weight and inertial mass are proportional to each other. Indeed living on the surface of the earth we often forget the difference between the two. One is still trying to find whether there is a miniscule difference between the two.

Let us now come to your question, reformulated as “how do we determine the mass of a planet”. One way is to find out the force of gravity on a test object placed at a given distance.

This is not practical for distant planets. Instead we use the fact that if the planet has a satellite at a known distance from it then the period of revolution of that satellite is a unique function of the mass of the planet.

The only approximation that we need to use is that the mass of the satellite should be very tiny compared to that of the planet.

In the following, allow me to use a couple of simple equations though they are not necessary for a qualitative understanding. For the satellite to be a satellite the force of gravity towards the planet should be balanced by the centrifugal force of circular motion (for simplicity we use only circular orbits for this argument). This means that

G M m/r2 = m v2 /r or v2 = G M /r or M = rv2 G

The period of the orbit is T = 2nr/v.

Here G is the known universal gravitational constant, and r can also be the known distance of the satellite. It is then easy to solve for M the mass of the planet by putting in the value of v in terms of the orbital period and r. Notice that the small mass of the satellite, “m”, does not enter into consideration in this simple treatment.

This is the way we know the mass of the sun, the earth and the other planets. There is no other way. All we have assumed is that if there is mass there must exist a corresponding gravitational field.

Since I have used a few simple equations you might think that I have given something complicated. Spend a little time on this and you will find that it is not so.

To summarise, the mass of the sun is determined by analysing the periods of rotation of various planets. The mass of the earth could have been estimated by observing the period of the moon but much more accurately now by the orbits of artificial satellites.

Masses of some of the other planets were also estimated by analysing the motions of their satellites. For some of the planets where proper natural satellites are not available we use the perturbations of orbits of artificial space probes.

The basis for all this is the belief that gravitational constant is universal, that mass must result in a gravitational field whose variation with distance is also known.

It might be interesting to know that that increased sophistication of measurement and calculation techniques has lead to the discovery of black holes and a large number of extra-solar planets. But the basic physics remains the same. In principle high school students could have made these discoveries!

What is optical density?

Optical density is, I believe, the power of refraction of light. It is usually given in terms of a number called refractive index. Some materials are more optically dense than others, for example diamond is far denser than water.

Some glasses called lead glasses are also denser than ordinary glass. The refraction arises from the fact that the velocity of light is reduced inside the medium in comparison to its velocity in vacuum.

In fact refractive index of a material is the ratio of velocities in vacuum and that in the material. Refractive index of water is 1.33 while that of diamond is 2.42. Preciousness of diamond for jewelry comes from this property.

In a finely cut diamond a lot light incident on its surface is total internally reflected from various surfaces because of the high refractive index.