Modern   meteorology   depends   hugely   on radiosondes, and hundreds of these balloon-borne instrument packages are released daily from weather stations all over the world. The sonde collects data up to a height of 18 miles (30 km), while being tracked in position using radar. The real-time data is continuously transmitted back to Earth by radio and the position of the sonde as time passes indicates the wind speed. Rising at the rate of about 0.2 miles (0.3 km) per minute, the flight usually takes about two hours. Silk weather balloons were first used to collect data in 1892 by the French scientist Gustave Hermite. In 1901 these were replaced by sealed rubber balloons. These burst when they reached a height of 12 miles (20 km), and the instrument package parachuted to the ground. The rest was left somewhat to chance because the flight records were picked up more...

Gyrocompasses have two great advantages over magnetic needle compasses: They point to the spin pole of Earth as opposed to the magnetic pole; and they are completely unaffected by the ferrous metal of a ship's hull or the magnetic fields produced by electrical currents running through nearby wires. Their main component is a motorized, fast-spinning, damped, gimballed wheel. When this wheel is not spinning exactly in the plane containing Earth's spin axis, an interaction between the angular momentum of the wheel and the angular momentum of Earth produces a restoring torque that pushes the wheel back into the true north-south orientation. A ship's gyrocompass is mounted in a complex set of gimbals that isolate the instrument from the ever- present pitching, yawing, and rolling. Aircraft gyrocompasses are even more complicated due to the higher velocity of the plane and the speedy changes in altitude during takeoff and landing. German scientist more...

"Gould [asked to use] the walkie-talkie idea... and he gave Dick Tracy that two-way wristwatch" Alfred J. Gross Walkie-talkies are the portable two-way radios that paved the way for mobile phones by showing the public the joys of talking to faraway people while walking around. In World War II they allowed troops to communicate and, since then, the police, the coast guard, and even children playing games have used them to relay information. Their exact origins are rather hazy though. Once radios had been invented, the next big thing was making them smaller and more portable and there is much disagreement over exactly when a two-way radio became a walkie-talkie, In 1937 a man called Don Hings, born in England and raised in Canada, built a waterproof two-way field radio. This radio weighed almost 12 pounds (5.5 kg) and was about the size of a toaster, but was definitely portable more...

India is a land of holy cities. Most of the important places of pilgrimage in India are located along the banks of the great rivers like the Ganga, Brahmputra, Godavari and Kaveri. Bathing in these rivers is considered a meritorious act. With the expansion of public transportation in the 20th century, it has become now easier for the people to visit these spots to partake of the divine. In fact, in India pilgrimage is the preferred form of tourism, which may be called religious tourism. The most significant religious place is Varanasi, which is also known as Kashi in south eastern Uttar Pradesh on the north bank of the Ganga, it is sacred to Hindus, Buddhist and Jains. They flock to the ghats or steps, leading from temples down to the banks of the sacred Ganga in their search for an auspicious site for death, cremation or immersion of ashes. more...

The game of cricket started in England first, but now it is played all over the globe and is very popular.  The game became very popular by the 18th century and a London club was formed in 1700. The Hambledon Club started in 1750 and at its ground, at Broachalf Penny Down, country cricket originated. Thomas Lord started a ground in Dorest Square in 1787 which was moved to St. John's Wood in 1814, and became the headquarters of the Marylebone Cricket  Club (M.C.C.), the ruling authority of the game. Gentlemen vs. Players, Oxford vs. Cambridge, and Eton vs. Harrow matches started about this time, and cricket took its present form. Cricket has achieved great popularity as can be seen from the jampacked stadia all over the world. There is always a clamour for tickets and yet many do not get any chance to enter. The game is played mainly more...

The deterioration of the environment by natural or human forces is known as environmental degradation. Natural happenings like heavy rain, floods, storms, earthquakes, volcanoes etc. are not under human control and they play havoc with environment time to time by making the land unfit for cultivation. Here man is helpless. He can do nothing except to see the havoc. But when man himself plays a vital role in degrading the environment in which he lives, then the problem becomes more serious. Needless to say that environmental degradation is one of the major global issues. The overuse of resources be it land or water and the industrialization process are the major causes of this phenomenon. Man has been felling the tress for his various purposes. He never minds if this process goes on without check it will lead to soil erosion, floods, silting of irrigation canals and cultivated lands, which finally more...

If you want to visit my father and do not know where he lives, just ask any one in the town and he would feel proud to help you find his home. People love him so much. It is because he spares time for their help. My father’s name is Mr. D.K. Raghav. My father was born on 26 January, 1962 at Varanasi. He received his early education in the same town and then went to Pune to study engineering. You might wonder, he has preferred to settle in a small town whereas he could have got a plump job in a major city. Once I asked him why he did so. He said, “Gandhiji said real India resides in villages and small towns. We must work there to bring India on the threshold of progress.” Presently, he is working as the Executive Engineer with the Public Works Department. My more...

The Ganga is the holiest and longest river in India. It rises in an ice cave known as Gomukh which is about 10,000 feet above the sea level. In its upper course, it joins with the Alaknanda and then rushes to Hardwar where its middle course begins. The Ganga then flows slowly by the cities and towns of Kanpur and Farukhabad. At Allahabad, it is joined by its biggest tributary, the Yamuna. The confluence of both these rivers here is considered very sacred by the Hindus.   After Allahabad, the Ganga moves eastwards flowing through Mirzapur and Benaras. Many people come here everyday to have a dip in the holy waters of the Ganga. Then the river which is by now a still large river as many tributaries and distributaries like the Kosi, Gandak, Ghaghara etc. join  it. It further moves by Patna, main flow of the river enters Bangladesh more...

No doubt war is an evil, the greatest catastrophe that befalls human beings. It brings death and destruction, disease and starvation, poverty, and ruin in its wake. One has only to look back to the havoc that was wrought in various countries not many years ago, in order to estimate the destructive effects of war. A particularly disturbing side of modern wars is that they tend to become global so that they may engulf the entire world. But there are people who  consider war as something grand and heroic and regard it as something that brings out  the best in man, but this does not alter the fact that war is a terrible, dreadful calamity. This is especially so now that a war will now be fought with atom bombs. Some people say war is necessary. A glance at the past history will tell that war has been a recurrent more...

“[Petzval] took on shortening [the Daguerreotype's] exposure time from minutes to seconds." Slovakia Today In 1839 portrait photographs took an age using simple meniscus lenses. 'All that changed when Hungarian mathematician Jozef Petzval (1807-1891) designed the first compound camera lens. The Petzval lens dramatically cut exposure times, boosted camera performance, and revolutionized photography. The "daguerreotype system," developed by Frenchman Louis Daguerre, was the forerunner to the Petzval lens. Requiring around half an hour of exposure time, this was still an improvement over existing techniques that needed several hours for successful exposure. However, this was still too long for taking portrait shots, which inevitably blurred with the slightest movement of the subject. Working with Friedrich Voigtlander at the University of Vienna, Petzval performed calculations that led him to create an achromatic portrait lens with four lenses arranged in two groups, providing six times the luminosity and an undistorted image for the more...