UNDERSTANDING THE UNIVERSE WITH PROF YASH PAL Does any object have zero weight? Since we are all made of the same stuff why are some people more intelligent than others? RESPONSE

Batteries go atomic
Shirish Joshi
Dr Amil Lal, an assistant professor at Cornell University, USA, and his colleagues have built a tiny battery, which could supply electricity to electronic sensors or implantable medical devices for decades by drawing energy from a radioactive isotope — radioisotope.

Coping with fog
M.S. Bhatti and Rajbir Bhatti
Fog is a natural phenomenon and reduced visibility is the first noticeable effect of fog. As such, fog is not deleterious to health but it is a nightmare for the vehicular traffic as it obstructs the visibility beyond a certain distance.

SCIENCE & TECHNOLOGY CROSSWORD

Batteries go atomic
Shirish Joshi

Dr Amil Lal, an assistant professor at Cornell University, USA, and his colleagues have built a tiny battery, which could supply electricity to electronic sensors or implantable medical devices for decades by drawing energy from a radioactive isotope — radioisotope.

Thermoelectric devices that use radioisotopes as a source of heat are being made and used as a source of electricity in spacecraft probing distant planets, oceanographic and meteorological instruments and pacemakers, that keep an ailing heart beating rhythmically.

Dr Lal’s device is said to utilise the electrons coming out of the radioactive material in a device, which vibrates.

It could directly move the parts of a tiny machine or could generate electricity useful for other devices. It is much smaller than devices made earlier to generate electricity.

The prototype is made up of a copper strip 1 millimetre wide, 2 centimetres long and 60 micrometres thick that is fixed on one end above a thin film of radioactive isotope of nickel (nickel-63).

One micrometre also called micron is equal to 0.001 millimetre.

As the isotope decays, it emits electrons. The emitted electrons collect on the copper strip, building a negative charge, while the film of isotope losing electrons, becomes positively charged.

The attraction between positive and negative charges bends the strip down. When the strip gets very close to the isotope strip, a current flows, neutralising the charge. The strip then springs up, and the process repeats itself.

The principle is much like that underlying an electric doorbell, in which a moving bar alternately makes and breaks the electric circuit supplying current to an electromagnet that moves the bar.

Radioactive isotopes can continue to release electrons over periods ranging from weeks to decades. The half-life of nickel-63, for example, is over 100 years. According to Dr Lal, any device using this isotope might continue to supply useful energy for at least half that time.

Unlike chemical batteries, the atomic battery will work in a very wide range of temperatures.

Possible applications include sensors to monitor the condition of missiles stored in sealed containers, battlefield sensors that must be concealed and left unattended for long periods, and medical devices implanted inside the body.

The moving copper strip can be made to produce linear or rotary motion. A magnetised material attached to the strip can generate electricity as it moves through a coil.

Dr Lal also has built versions of the device in which the moving strip is made of a piezoelectric material that generates electricity when deformed, releasing a pulse of electricity as it moves up and down.

The device ordinarily operates in a vacuum.

Dr Lal and students Hui Li and Hang Guo are now building and testing practical sensors and power supplies based on the concept. The prototype demonstrated in August, 2002, was very large by comparison with the latest versions.

An entire battery could be made to fit in less than one cubic millimetre.

Coping with fog
M.S. Bhatti and Rajbir Bhatti

Fog is a natural phenomenon and reduced visibility is the first noticeable effect of fog. As such, fog is not deleterious to health but it is a nightmare for the vehicular traffic as it obstructs the visibility beyond a certain distance.

The origin of fog is due to a multitude of factors like humidity, pressure, temperature, wind and inversion. Humidity is nothing but water vapour present in the atmosphere. Thus, higher the temperature more is the water vapour air can hold, before it becomes saturated. At the ground level, a temperature increase of 11.1°C approximately doubles the moisture capacity of the atmosphere. Saturated air at 16°C thus contains roughly twice as much water vapour as saturated air at 5°C.

Fog is a phenomenon that occurs in the lower part of the troposphere and extends only up to a few hundred metres (less than 1 km above the surface of earth). This is due to radiation (temperature) inversion that occurs due to unequal cooling rates of earth and air above the earth. Radiation inversion along with humidity promotes the formation of fog. During inversion, atmosphere near the earth is cooler than air above, thus it hinders the dispersion of water vapours in the upper atmosphere. In the morning, the sunrays cause the earth to heat up and this breaks the inversion and leads to dispersion of fog in the upper atmosphere. The strongest inversions occur in winter and weaker ones in summer when the air is still. During winter nights and days there is an inversion more than 50% of the time.

During fog, drivers switch over to yellow lights. One could argue that red due to its maximum wavelength (VIBGYOR) should be the preference; but red suggests danger. Orange is ruled out due to poor distinction from red. There is another scientific fact that water particles (that’s what fog is made of) glow in a white light. The yellow light does not cause the glowing effect but basically just losing a bit of power and goes through the particles that are on its way. Hence, yellow light provides the best option available. If you try to use regular high beams in the fog-all you will see is the white wall in front of you and it makes driving very difficult. Low beams create a smaller white curtain. A lowered yellow fog light penetrates underneath the fog and does not create a glowing effect. One can see much far with them resulting in safe driving.

Instead of covering the headlights with yellow paper or putting yellow lights on the roof of the car, the correct strategy is to install the yellow lights on the bumper of the vehicle, not more than 1 ft from the ground level for better penetration. This is because fog usually hangs 1 ft above the ground. If you lay down on the road-you will be able to see the surface of the road clearly. That’s the reason why fog lights are installed low. The fog lights don’t work as good on heavy vehicles because of more height at which they are installed.

Given below are a few valuable tips that could help in safe driving:

* Good halogen/yellow lights mounted not above 1 ft from the surface of the earth.

* Preferably keep low beam of headlight; high beam could lead to formation of white wall (scattering) in front of the driver and hamper visibility.

* Fog lights must be properly adjusted.

* Don’t close all the windows in case of four wheelers to avoid moisture on the front/wind screen. AC for dehumidification and heater for warmth may be made use of.

* The low level clouds with no wind on the preceding day during winter indicate fog.

* The use of horns and emergency indicators are further recommended for sale driving.

* The golden rule is always, slow driving is safe driving.

The latest strategies to intimidate fog include seeding clouds with silver iodide or dry ice so as to precipitate fog. Considerable research efforts have suggested fog dispersal as a method for increasing visibility of aircraft. Most of the experiments are aimed at achieving artificial precipitation of fog. Hi-tech equipment like radar echoes, ceilometers and transmissometer ensure smooth take-off and landing of aircraft in fog.

In conclusion, fog which is a nocturnal phenomenon that breaks up with the morning sunrays cannot be eliminated but can definitely be subdued by adopting the methods like yellow headlights etc as mentioned in this article. A wise and rational use of the aids at hand could ensure your safety.

UNDERSTANDING THE UNIVERSE
WITH PROF YASH PAL

Does any object have zero weight?

This innocent sounding question requires some detailed consideration. Scientists distinguish between the words “weight” and “rest mass”. In ordinary life on earth the two are the same. Rest mass or — more simply — mass and weight are proportional to each other and the measuring units are so chosen that they are the same. What we determine by weighing with a balance is the weight. This is the force with which the earth attracts the object because of the force of gravity. However, if the same object is in orbit around the earth, it is freely falling towards the earth and is weightless. If you were that object and stood on a balance while both you and the balance are orbiting the earth the balance will show a reading of zero. Both the balance and you would be weightless, even though both will have the same mass as they had on the surface of the earth. Therefore, I will assume that you are interested in finding out whether there is any entity in the universe that has zero “rest mass”?

The answer to the last question is yes. The very obvious “object”, if you can call it that, is light. Light photons have energy but zero rest mass. In addition there are other particles called neutrinos that have zero or near zero mass. The existence of neutrinos was theoretically postulated to explain certain observations. They have been experimentally observed since then. There is some recent evidence that their mass may not be exactly zero but they are close to being mass less.

Mass less particles have a central role in the universe. This is obvious as far as light and heat are concerned. It has been found that neutrinos are basic in determining the nature and evolution of the universe.

The point to appreciate is that even though we come from the same material, the combination of the same genes, we are not like coins stamped out by a machine. Chance and statistics also come into play during inheritance.

RESPONSE

This refers to the answer of Professor Yash Pal to the second question, “Since all natural products are from plants, why do they differ so much in taste” covered under serial “Understanding the Universe” (Jan 9).

Kindly permit me to supplement the answer as under:

All plants are made up of a set of elements. It is the arrangement and the number of these elements that make them morphologically and constitutionally diverse. As a corollary, although diamond and graphite are constituted by carbon, yet their properties are different. It is the arrangement of carbon atoms that makes all this difference in terms of structure, lustre and properties of the two. The same is true with the gene — arrangement of four bases that differ in number and the sequence — makes all the difference. In case of plants also, the constituents differ in terms of relative contents. It is the cumulative effect of all the constituents that results in difference in taste. Otherwise, pure glucose, irrespective of the plant source tastes sweet. When the constituents combine in different ratios, varying properties, including the taste, results.

R.K. Kohli,

Chandigarh

SCIENCE & TECHNOLOGY CROSSWORD

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