SCIENCE TRIBUNE Thursday, June 29, 2000, Chandigarh, India

Dark matter in the universe
by Nataraja Sarma

HYSICS has always said that there is a lot around you that you cannot feel with your five senses. Astronomers now realise this to be a true statement. They search for new objects in the sky through optical radio telescopes or telescopes but all celestial object do not emit light or radio waves.

Cybersurfing with Amar Chandel
How it works
Science Quiz

New products and discoveries



Dark matter in the universe
by Nataraja Sarma

PHYSICS has always said that there is a lot around you that you cannot feel with your five senses. Astronomers now realise this to be a true statement. They search for new objects in the sky through optical radio telescopes or telescopes but all celestial object do not emit light or radio waves.

They do, however, pull nearby stars through gravitational forces and disturb their movement through the universe. Recording the motion of nearby stars, therefore, helps detect heavenly objects that are invisible to us. Astronomical observations of galaxies carried out over several decades clearly indicate that all optical and radio telescopes and other instruments on earth see only a fraction, a mere one-tenth of the universe.

In the 1930s scientists examined closely two relatively nearby clusters, the coma cluster and the virgo cluster. They studied individual galaxies within these clusters as well as velocities of the clusters. Surprisingly, the mass of the cluster worked out to be far more than computed from those of the galaxies. More detailed work later found that the galaxies themselves were much heavier than was earlier estimated, and that the extra mass was invisible. This was the first direct evidence for dark matter in the universe.

If the total mass of the universe is very large, beyond a critical limit, gravitational pulls will make it collapse on itself-rather like overloading a camel! On the other hand, if the mass of the universe is too small, gravitational forces are too weak to keep the universe together and it will forever expand. In between lies what we think is our stable universe.

A number called Omega=1 designates the extent of the stability. Adding up all the mass we can see in the heavens gives an extremely small value of Omega=0.05. In other words, we cannot see 95 per cent of the universe!

Physicists have put forward several theories about the nature of this dark matter. It cannot be planets that circle stars, like the earth, because they neither contribute only a very small amount to the star mass, nor can it be Brown Dwarfs, the stars that were too small to burn and shine.

Theorists generally agree that the Big Band gave birth to our universe. An infinite amount of energy was concentrated in an infinitely small volume and this resulted in an enormous explosion. As the new-born universe cooled, quarks and gluons were formed and they then condensed into heavy nuclear particles (baryons) and light particles (leptons) such as electrons. These united in various combinations to produce ultimately the chemical elements. The abundance of the elements as we observe today comes out exactly that all the initial provided baryons and leptons gave rise to a value of Omega= 0.1. One might question the Big Bang theory on the grounds that the Omega value should have been larger, but then it has been so successful that other explanations have to be found.

There are so many neutrinos floating around the universe that some theorists suggest that they could make up the necessary dark matter./ After all, neutrinos interact insignificantly with matter that they could be the main component of dark matter. Very light particles like neutrinos reach enormous speeds and such dark matter will have a light temperature and not be uniformly distributed. This may result in clusters and super-clusters lying along planes and long strings with wide open spaces between them, as is seen. However this requires that the neutrinos need to have some mass, even if it be small. But it has not yet been confirmed whether a neutrino has a mass at all.

Reaching out for exotic ideas, enterprising physicists have proposed the existence of weakly interacing massive particles, or WIMPS. These heavy WIMPS will form structures among the stars that are relatively small, about the size of galaxies. It is, however, possible that dark matter is a mix of light and having objects.

Heavy particle like neutrons and protons interact strongly with other particles. They collide with other particles and with nuclei and so leave a trace of their accidents in equipment such as the cloud chamber or the bubble chamber. Because of their weak interaction, WIMPS pass right through ordinary matter. They would not leave their footprints on earth and that is why have not been detected in spite of several large and expensive searches. These strange objects bear exotic lables like neutralinons, axions, s-neutrinos or Higginos. They could also be nuggets of strange quark matter, according to some theories. Occasionally though, they might hit an atomic nucleus.

A team of Italian and Chinese scientists recorded 13 such hits in their apparatus. They found evidence of such collisions and stated that the earth is moving through a cloud of WIMPS at about 225 kilometers per hour, the speed at which the sun moves around the centre of the galaxy. In addition, as it revolves around the sun, the speed of the earth through the universe varies from season to season, and so the number of WIMPS detected should change-and the group believes it has seen such a variation.

A group from Stanford University in the USA contradicted these findings. They built heavily shielded, ultra-cold detectors that can specifically identify and reject many types of spurious interactions caused by natural radioactivity and the high-energy particles arriving from space called cosmic rays. They said that they did not find any WIMPS in the one year that they has looked for them. The 13 events they did find in their detector were ascribed to stray neutrons from decaying nuclei. While most physicists agree with the Stanford claims, they do not rule out that the Italians could have made one of the most important discoveries in cosmology.

Several scientists thought that both results could eventually turn out to be correct after the Stanford group admitted that their detector might have seen two or three WIMPS among the neutron that they counted. The uncertainty lies in the fact that a large background must be eliminated from the observed signal. Both the Italian and the Stanford scientists plan to upgrade their equipment to decide if WIMPs exist.

Finally, if in desperation, one says that it is all because gravity misbehaves on the scale of the universe, this too may well be correct. — (PTI) 


Cybersurfing with Amar Chandel

Web-based health-care venture

Indian Medical Portal Pvt Ltd, a new entrant to the health-care service, has launched as a vehicle for its participation in various segments of the health-care business. At present, the portal addresses its contents to medical practitioners and health-conscious consumers. Segments for hospital administrators, retail pharmacies and students of medicine will be added soon.

The portal incorporates a large volume of consumer-education material on diseases and their treatment. It is written in a simple and lucid language to give consumers greater confidence in dealing with their physicians, and accepting greater responsibility for recovery and physical well-being.

Then there is a Physicians’ Prescription Guide (PPG), which claims to be India’s first comprehensive prescription database, comparable to the Physician’s Desk Reference published in the USA by the Medical Economics Co. since 1946. In view of the risks of irresponsible self-medication, access to the PPG has been restricted to registered medical practitioners. The guide currently covers over 2,000 allopathic brands owned or marketed by 60 companies. It is being enlarged to report 8,000 brands of 400 pharmaceutical companies by August 1.

Interestingly, the company has commenced work on a similar database project for ayurveda, siddha and unani formulations. It is to be released by August 1.

The development of a Hindi version of the portal has also started.


IT is said that there is a galloping gourmet in all of us. If your are like the majority which digs food and cooking, have a look at that should be one of the most comprehensive websites on the subject with everything from kid-friendly recipes to meatless menus. There are also cookbooks, reviews and chat forums.

The most useful sections are on dining table etiquette and “1001 cooking tips”. For instance, did you know that there are two styles for cutting: the two-step European (or Continental) style and the four-step crossover American style. Both are acceptable.

In the two-step cutting method, the knife is held in the right hand (unless you are left-handed, in which case you may reverse these directions) and the fork in the left throughout the procedure. With the tines of the fork facing down, the food is cut and the fork brought to the mouth, tines down.

In the four-step method, the fork starts in the left hand, the knife in the right, and the main dish is cut. The knife is then placed flat on the plate, and the fork is switched to the free right hand and turned right side up in the process. It is brought to the mouth in the right hand.

When resting between bites, place the knife and fork, handles to the right, on the plate. Never rest them on the table. When you’re finished, place the flatware side by side, across the middle of the plate, handles right, to secure their removal.

Food is always served from the left, and the silver service fork is placed to the left of the spoon, with both utensils angled in toward the food so that they can be easily picked up by the next person served. Also, start eating hot food when it is served - don’t wait for everyone to begin. 


How it works

Communication satellites

THE use of satellites as an integral part of global communication systems has progressed rapidly over the last decade. Each new generation of satellite is technologically superior to its predecessors. These advancements have significant impact on the development of military applications, domestic and international communication systems.

The era of 1920s saw the advent of long-range communications through modulated microwave electromagnetic fields. These became an integral part of terrestrial (ground-to-ground) and near-earth (aircraft) communication system. These systems were restricted to line-of-sight links i.e. the communication was possible only by ground transmission relay methods. The use of tropospheric and ionospheric scatter to generate reflected skywaves for the horizon links was unreliable for establishing a continuous system.

The year 1956 saw the advent of Echo-satellite. This is a metallic reflecting balloon placed in orbit to act as a passive reflector of ground transmission to complete long-range links. Then, came the active satellites like Score, Telstar, and Relay.

The three categories of satellites used for communication are: GEO-the geostationary satellite, MEO-the medium earth orbit satellite, and LEO-the low earth orbit satellite. In the real sense, satellite communication started with the GEOs. They are positioned at an orbit height of 36000 km and revolve around the earth once in 24 hours. Due to this reason the GEO appears stationary as viewed from the earth. GEO has a disadvantage that it does not cover the polar regions owing to poor elevation at higher altitudes. Further, the GEO requires high power and the large distance between the earth and the GEO causes a high propagation loss of about 175db and time delay of the order of 250ms.

MEOs are located at an orbit height of about 11,000 km and the LEOs are placed at an orbit height of approximately 1900 km. This way the LEOs overcome the demerits of GEO satellites. LEOs are of two types viz. ‘Big LEOs and’ Little LEOs. Little LEOs have satellites, which are smaller and have less weight. These are generally used for non-voice applications. Big LEO group consists of MEO and ICO. They provide high quality voice service, paging, fax and data communication. Iridium, Globalstar and Odyssey are some of the examples of big LEOs. A constantly moving switching network and an antenna enables communication in LEO. This is in contrast to fixed GEO system. Mobile communication in LEO is dependent on relative mobility. Here the LEO systems move, and the roaming users appear stationary.

Communication based on GEO is single hop, whereas the LEO based communication is multiple hop. Further, the LEOs are low cost and have less weight. Cellular technology can only cover a certain amount of terrestrial areas. As the distance between mobiles and the traffic increases, global satellite coverage becomes more cost effective. Only satellites can provide wireless global coverage. LEOs have given a significant boost to satellite communication and are a media for all communication services.

— Deepak Bagai


Science Quiz


  1. British physicist Lord John Rayleigh was awarded the 1904 Nobel Prize for Physics for his discovery of the argon gas. Name the other scientist who also won this coveted award for the same year and the same discovery. For which discipline was he awarded this prize?

  2. Copper, tin and zinc constitute an alloy which is mainly used these days to make machine parts. In the beginning this alloy was used for making a defence weapon from which its popular name was derived. What is this popular name?
  3. Optical telescopes in which only lenses are used are called refracting type and those in which only mirrors are used are called reflecting type. What are those telescope called in which both lenses and mirrors are used in combination?
  4. Elastic materials are those materials which change their shape and size under mechanical stress. What are those materials called which change their shape and size under the influence of electric and magnetic fields?
  5. The female glow worm has a wonderful natural lighting system and produces light by a chemical process using the natural chemical “lucifern” present in its abdomen. It also has a remarkable ability to control this light and “switches’ it on only for a specific purpose. What is this purpose?
  6. This bird of New Zealand is only marginally larger in size than a hen. But its egg is about eight times bigger than that of a hen. Which bird are we talking about?
  7. Name the device in a word processor of a computer which corrects the grammar in the copy and also tells you how good a writer you are.
  8. Planets Jupiter, Saturn, Uranus and Neptune have relatively low density and are mainly composed of hydrogen and helium. What is the name given to this group of planets?
  9. Can you state the precise value (correct upto second decimal place) of the ice point on the absolute scale of temperature?
  10. This forest is the world’s largest tropical forest and is home to 50 per cent of the world’s plant and animal species. Hundreds of Brazilian environmentalists staged a unique protest march recently against its devastation by the expanding agricultural farming. Which is this forest?


  1. Scottish scientist Sir William Ramsay for Chemistry, 
  2. Gunmetal
  3. Catadioptric telescopes
  4. Electroactive and magnetoactive materials
  5. To attract its male partner for mating
  6. Kiwi
  7. Lexical analyser
  8. Jovian planets
  9. 273.15K
  10. Amazon rain forest.



New products and discoveries

“Richard the first” robot

Don’t mistake “Richard the first” for an ordinary robot. It can perform functions which would delight any harassed householder.

Built by senior students of the Strathclyde University of Norway, “Richard” is equipped to do troublesome household chores like painting the walls, cleaning the car, mowing the lawn and shoving snow off the driveway.

A sophisticated pre-programmed chip in the robot makes all these tasks not just possible but pleasurable as well. For even as it does the cumbersome work which is the bane of any household, Richard’s in-built stereo system provides music as you watch it.

Helmet copies skull’s movement

To reduce the prevalence of head injuries — one of the commonest cause of death among the young — a British scientist has designed a new helmet which, by simulating the natural protective mechanism of the human head, improves user safety.

Called Phillips Helmet, it can be applied in any situation where a helmet is necessary and has been shown by the United Kingdom's Transport Research Laboratory to provide up to 60 per cent more protection than standard helmets.

The helmet embodies a soft, elastic, moveable outer layer that simulates the scalp and provides protection against rotational acceleration. It covers a hard, laminar shell simulating the skull and provides protection against linear forces and crushing, reports British Commercial News.

New sensor to help car drivers

GOOD news for car drivers who are in a fix on when is the right time to change engine oil.

A new sensor developed in Germany can be installed in engines to measure parameters like viscosity and electrical conductivity of the oil, thereby determining the condition of the engine lubricant, according to a report in Fraunhofer Geselschaft Research News.

Bones grown in lab

EUROPEAN scientists are growing bones in the laboratory with the goal of developing replacement grafts for people whose bones have been injured in accidents or who are suffering from arthritis, reports New Scientist.

The technique entails taking cells of bone marrow and growing them in a culture.

The cells are then mixed with compounds to promote bone growth and “seeded” onto a tough substance called hydroxyapatite which is the mineral basis of bone.

Video on the Net

GLOBAL VideoCom Group, PSINet and 1414c, a wholly owned subsidiary of PictureTel Corporation, have announced an alliance to provide “Video-on-the-net”, the world’s first business quality videoconferencing service.

Video-on-the-net accelerates business access to state-of-the-art-web-based videoconferencing, eliminating the barrier-to-entry requirement for investment in expensive hardware and software.

The service enables companies to host multi-user videoconferences using high-speed IP networks. The ASP service empowers organisations to harness applications that take full advantage of the broadband IP revolution.

It also provides to a wide range of IP-based interactive communication solution, including live multi-point videoconferencing, video-streaming and broadcasts, video-on-demand, data-sharing, voice-over-IP and access to corporate Interanets.

Organisation will be able to book, schedule and deliver a robust range of interactive solutions using a browser.

Cisco core service

CISCO Systems Inc. has introduced its core service offering in the country - SMARTnet and SMARTSpares. This bring a new dimension of networking service and support for Cisco’s customers and enables its resellers and partners to tailor support solutions to assure customer networks of optimal uptime, utility and flexibility.