Chandigarh, Thursday, November 19, 1998 |
Cosmic fireworks & orbiting spacecraft by Pravin Kumar ON a clear night, well away from city lights, you will most probably see bright streaks of light across the sky, at the rate of four or five in an hour. These are popularly called shooting stars or meteors-extra-terrestrial debris ranging in weight from 0.1 gm to a few kilograms. Travelling at 72-km per second, they get heated and vaporised. The light is due to the heat generated by friction with air and to the ionisation of air molecules. Leonid
storm is no light matter Cybersurfing with Amar Chandel Web software for the blind Your home and pollution Science Quiz
|
Cosmic
fireworks & orbiting spacecraft ON a clear night, well away from city lights, you will most probably see bright streaks of light across the sky, at the rate of four or five in an hour. These are popularly called shooting stars or meteors-extra-terrestrial debris ranging in weight from 0.1 gm to a few kilograms. Travelling at 72-km per second, they get heated and vaporised. The light is due to the heat generated by friction with air and to the ionisation of air molecules. Meteors become visible at heights of around 190 km and get burnt out before they drop below 80 km. The brightest meteors may outshine the full Moon and are then termed fireballs. Occasionally the sound of their passage can be heard. Meteors which explode are called bolides. Those projectiles which are big enough to survive the fiery passage through the Earths atmosphere and impact the Earth in the form of rocks are called meteorites. In addition, there are smaller particles with diameter of 5/1000 inch which have no luminous effect; these are called micro-meteorites. They are also different in composition from the bigger meteorites. Collectively, these visitors from space are called meteoroids. The outsize meteorites make a large crater when they hit the Earth. A famous example is the Great Meteor Crater (strictly, it should be Meteorite Crater) in Arizona (USA); this was produced by a meteorite that hit about 20,000 years ago. Lonar Lake in Buldana district, Maharashtra, is also believed to represent the site of a meteorite hit. Mostly, meteors are sporadic and travel round the Sun in elliptical orbits. They may appear at any moment and from any part of the sky. Those that travel in shoals are the shower meteors that are responsible for spectacular displays, often at specific times of the year. Due to the laws of perspective, these appear to arrive from a particular point in the sky (the radiant) just as parallel lanes on a highway, or railway lines, will seem to radiate from a point near the horizon. Meteor showers are generally named after the stellar constellation that contains the radiant. Thus, the Perseids, which occur from July 23 to August 15 every year, radiate from Perseus. When two or more showers have radiants in the same constellation, they are named after a nearby bright star, e.g., the Eta Aquarids. Several showers are named after the comet from which they are derived. The richness of the shower is given by the Zenith Hourly Rate (ZHR); this is the number of naked-eye meteors expected to be seen by an observer with the radiant at the zenith or overhead point. The actual rate may be less than the theoretical rate. When the number of meteors is high, it is called a meteoric storm. Meteorites are derived from asteroids in the asteroid belt, between Mars and Jupiter; in fact, asteroids like those belonging to the Amor and Apollo group have orbits crossing Earths Meteors, on the other hand, originate from short-period comets with periods of less than 200 years. As a comet nears the Sun, the material of its nucleus breaks off due to solar radiation and heating, as well as pressure effects. The particles which separate from the comet go into an orbit corresponding to the parent comets orbit. Over time, gravitational and other effects distribute the material more uniformly around the orbit. When the Earths orbit intersects the orbit of the debris we see shower meteors. Comet Halley, which visits the Earth every 75 years, on an average, is linked with two showers, the Eta Aquarids (5 May) and the Orionida (21 October); these may contain 10 times the total mass of the comet nucleus, which gets whittled down every round trip. However, due to perturbations by the giant planet Jupiter, a comet as well as its meteoroid stream may cease to intersect the Earths orbit in the future. On the other hand, some meteor streams have intersected the Earths orbit for hundreds of years. The Lyrids were first recorded in 687 BC and the Leonids in A 902. Bielas
comet The Leonid showers, which get their name from the constellation Leo, are coming this week (with a peak at 2.10 a.m. on November 18). The meteors are bunched up, instead of being spread all round the orbit, so the best displays occur every 33 years, when Comet Tempel-Tuttle (period, 32.9 years) is close in. In 1866, the display was so spectacular that snowflakes seemed to be falling from the sky for four hours. The next display was due in 1899, but, due to planetary perturbations, the main cluster was missed. The 1966 return of the Leonids was the greatest celestial show of the century, the ZHR reaching 100,000 in Arizona (USA). This months display could be scintillating, predicts the celebrated astronomer Patrick Moore in his book The Amateur Astronomer. Risk
to spacecraft Some communication companies believe that the Leonid showers will damage every second satellite. When a dust particle hits a satellite, matter burns up, causing an electrical discharge which will damage the satellites on-board computers. To prevent damage, the Hubble Space Telescopes expensive mirrors are being turned to minimise the chances of their being hit by meteoric dust. According to the Indian Space Research Organisations (ISRO) release, the probability of the five INSAT satellites and the four IRS satellites being hit is 0.01 to 0.03 per cent. The solar panels of the satellites, which generate electricity from photo-voltaic cells, will be turned in such a way as to present the smallest surface to the oncoming meteoroids. Because of the risk to spacecraft from meteoroids, attempts have been made to measure their flux in space by means of HEOS, Helios and Pioneer spacecraft. Micro-meteorite collectors have been deployed from the MIR space station and are planned for the Space Station Freedom, to be launched in December 1998. Apart from the threat to spacecraft, meteoroids are of interest because, being the oldest material objects on Earth, their origin may throw light on the evolution of the early Solar System. Some contain even older grains that may have survived unaltered since their formation near other stars. Their varying composition suggests that they are from many sources; hence, they provide samples of dozens of different solar system bodies. Broadly,
meteoroids are of two types stones (aerolites) and irons
(siderites). These rocks provide detailed information on
mineral structure and elemental composition which
telescopes and aircraft cannot provide. Last year,
scientists at Arizona State University (USA) found large
amounts of left-handed aminoacids in the Murchison
meteorite which landed in 1969 in Australia. Amino-acids
are the building-blocks of proteins and are fundamental
to organisms, but their discovery in the meteorite means
that one-handed organic molecules predate life and might
have been present in the material from which the solar
system grew. |
Leonid storm is no light matter The last Leonid storm, in 1966, did not evoke so much interest, for only a few spacecraft were in orbit. The parent comet Tempel-Tuttle reached perihelion (point nearest the Sun) on 28 February, 1998, precipitating a meteoroid shower through which the Earth and about 500 operational satellites (6 per cent of the total of 8000 in orbit) will plough. In a paper published in Current Science journal Dr T Parimala Rangan and associates from ISRO Telemetry Tracking and Command Network, Bangalore, have worked out the combined effect of factors like the impact probability, the relative velocity of the meteoroids, orientation of the spacecraft to meteoroids, etc., upon which will depend the damage suffered by the satellites. Their analysis indicates that all Indian satellites serving scientific, communications and remote sensing missions are certain to undergo this ordeal... and Earth will not protect the satellites as the orbital planes will be exposed to the storm (which lasts about five hours.) Though the impact probability for Indian satellites is low, an actual impact could be catastrophic. The
meteoroids could damage satellites or their components,
cause pitting of optical surfaces and mirrors, though
physical damage to the solar panels is unlikely as the
meteoroid storm will approach edge-on to the sun-tracking
solar panels. |
Cybersurfing with
Amar Chandel Making good paintings is only half the battle won. Getting them well displayed comes in the other half. Booking art galleries and paying their hefty charges has frustrated many a promising artist. Enter the Internet. Many websites have started exhibiting art works. But the problem is that most of them are commercial sites charging hefty fees to display ones works. But at the same time, there are quite a few non-commercial websites that show artworks exclusively of their liking but without charging any money. The Garret Gallery is one of them which is run by a well-known art collector, Mr Drummond Mile, who is based in Mumbai. It can be accessed at www.gadnet.com/garretm.htm. Incidentally, for this month, it has chosen Chandigarhs very own Balvinder for display. He is perhaps the first artist from the region to be thus honoured. Another art gallery worth frequenting is at www.chitrakoot.com. It features several artistes such as Ganesh Haloi, Manoj Dutta and Sanat Kar. Those with a poetic bent of mind should try out freespace.virgin.net for downloading a sort of notepad-cum-thesaurus. The Random Verse Lab (RVL) software can help them write poetry. One can create ones own templates by specifying where one wants verbs, nouns etc to appear. After that, the software take over. The results may not be very flattering but those are your own creations, after all. * * * * There are search engines and search engines. Everyone has his or her own favourites. I stumbled on one which combines the strength of all of them. Ask it to search something and it utilises the combined capacity of several search engines to come up with a vast list of results. It has been appropriately christened www.mamma.com. Like a true traditional mamma, it goes to considerable pains for you. Try it out. Particularly helpful are sites on fun and entertainment. * * * * And here is something which may warm the hearts of women. Here is a whole site (www.queendom.com) to help them improve their personality. There are numerous personality tests, intelligence tests, tips on attitudes, lifestyle and emotional health. Then there are brain teasers and puzzles which put you on your way to natural leadership. Men can take heart. Although the main chunk is devoted to women, there are any number of helpful hints for men as well. In any case, all those tips that are good for the fair sex are good for them as well, no? * * * * Like it,
dislike it, debunk it ... but you cannot ignore
astrology. It has as many diehard supporters as it has
cynics. For the former, one recommendable site is
www.astrology-online.com which gives you your overall as
well as time-specific predictions in a jiffy. One can
also learn quite a bit about astrology through various
sections and also surf on to various other links. |
Web software for the blind IBM researchers have developed a software that will help blind people read text on the World Wide Web (WWW) over Internet. The software, developed by researchers at IBMs Tokyo Research Laboratory, is available in Japanese and an English version is under way, reports IBM Research. It is inspired by IBMs Screen Reader TM 2, which can enable blind persons to access the Netscape Navigator TM Web browser. The problem is that the software reads text-based information only, and is therefore, not suited to the Internets multimedia environment, which contains embedded images and hyperlinks. The new software is capable of interpreting the Weds special coding. One of the biggest challenges, according to team leader Chieko Asakawa, was devising a simply way to navigate as blind people can not use the mouse. The
solution was to use the computers numeric keypad.
Once online, the package called Homepage Reader announces
the default home page, and the surfer can use a number of
keys to move between pages, lines and individual
characters. If the user wants to read something, he just
double-clicks key 2 and the system reads the page from
the beginning. Other keys let the user fast-forward,
rewind or jump to the next link on the page. When the
reader arrives at a hyperlink (a piece of text or
graphics in a document which when clicked takes one to a
related web site), the voice switches from male to female
a cue that Asakawa deems intuitive and
natural. |
Your home and
pollution THINK pollution and you think of smokes emanating from factories and dusty roads. We scream ourselves hoarse about how advances in technology have ruined the environment, and our health too. But do you know that your own home offers no better a situation! Lots of people, who suffer from sneezing, bronchitis, minor coughs, eye irritations would be surprised to know that the source of their irritation is lurking in their own homes. Check out the hidden sources of pollution and what you can do to control them. 1. Air Freshners of your room: Solid deodorisers release paraperidichloro benzene, a chemical that is suspected to cause cancer, as they melt into the air. Allergeologists say that the best way to freshen your rooms is to keep them well-ventilated. Allow fresh air to move freely in and out of the house. 2. Beating the mosquito menace: Mosquito repellants emit smoke and along with it they also release a chemical which which leads to bronchial problems and pharyngitis. The best method of coping with the mosquito menace is to use meshes on windows or bed-nets. 3. Cigarette smoking is dangerous to health: Cigarette smoke gives both the smoker and everyone else in the house an unhealthy dose of more than 4000 chemicals. Second had smoke can irritate your eyes, nose and throat and it may even lead to lung cancer. So take a hard line against smoking in your home. 4. Vent out agarbatti fumes: The incense sticks you light in your home could irritate the respiratory system of asthmatics. So when you light them, dont overdo it and make sure that the room is well ventilated to allow the fumes to go out. 5. Back out the car: Gasoline engine exhaust is a deadly source of carbon monoxide. So do not let your auto run in idle in an attached garage. 6. Air out dry-cleaned clothes: The chemical used to dry-clean your clothes i.e. tetrachloro ethylene, has been known to cause cancer in animals and could as well cause cancer in humans, too. Airing out of these clothes before storage to cut pollution levels is advised. 7. Clean, clean bathroom: Everyone likes clean bathroom, but be careful while using toilet cleaners. The chemical phenol that is released is known to cause shortness of breath and sneezing. 8. Can
plants reduce pollution levels: Some plants like neem and
tulsi and also bamboo palm, chrysanthemums and ferns,
have been known to clear the air. But there is also a
warning. Dont overdo it. Too many plants can cause
breathlessness. Besides, plants give out carbondioxide at
night, so when the sun goes down, put your plants
outside. |
Science Quiz 1. Name the internationally recognised entrepreneur and agricultural expert Indian farmer who has recently been awarded this years World Food Prize for promoting private enterprise in Indias agriculture sector. To which state does he belong? 2. Some farmers of Maharashtra have developed a wonder manure which, they claim, can help grow bumper crops of vegetables, fruits and trees. What has this manure been named? In addition to having cow dung and groundnut cake as its main ingredients, which three chemical fertilisers are used in preparing this manure? 3. ENG refers to a process related to the production of newspapers. What does ENG stand for? 4. Roslin Institute of Scotland which cloned the sheep Dolly has been accused of pirating a gene from a rare and nearly extinct dwarf breed of cattle only found in Kerala. Which is this cattle breed and what is special about it? 5. Garlic is known for its medicinal properties. A potent antibiotic drug is extracted especially from garlic. Name this drug. 6. The blood of an insect which has green body and eats green leaves of plants is white in colour. This insect can be seen in house gardens. Name this insect. 7. Snowball, Spider, Pompon, Spoon and Reflexed are only a few of hundreds of varieties of this delicate, multi-coloured and magnificent flower that blooms in November and December. Which family of flowers are we talking about? 8. North India will soon have a highly sophisticated giant telescope that would enable astronomers to view the entire universe up to its edge and would use solar energy for generating power for its functioning. Where is it being set up? 9. Suggest one word for the use of electrical signals to transmit medical information with a view to overcoming the barriers of time and distance. 10. Name the city of India that is fast becoming the industrial hub of information technology and has come to be known as Cyberbad. Answers |
H |
| Nation | Punjab | Haryana | Himachal Pradesh | Jammu
& Kashmir | Chandigarh | | Editorial | Business | Sports | | Mailbag | Spotlight | World | 50 years of Independence | Weather | | Search | Subscribe | Archive | Suggestion | Home | E-mail | |