Ozone Depletion

November 14, 2008

The ozone layer can be depleted by free radical catalysts, including nitric oxide (NO), hydroxyl (OH), atomic chlorine (Cl), and atomic bromine (Br). While there are natural sources for all of these species, the concentrations of chlorine and bromine have increased markedly in recent years due to the release of large quantities of manmade organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons.[3] These highly stable compounds are capable of surviving the rise to the stratosphere, where Cl and Br radicals are liberated by the action of ultraviolet light. Each radical is then free to initiate and catalyze a chain reaction capable of breaking down over 100,000 ozone molecules. Ozone levels, over the northern hemisphere, have been dropping by 4% per decade. Over approximately 5% of the Earth’s surface, around the north and south poles, much larger (but seasonal) declines have been seen; these are the ozone holes.


On January 23, 1978, Sweden became the first nation to ban CFC-containing aerosol sprays that are thought to damage the ozone layer. A few other countries, including the United States, Canada, and Norway, followed suit later that year, but the European Community rejected an analogous proposal. Even in the U.S., chlorofluorocarbons continued to be used in other applications, such as refrigeration and industrial cleaning, until after the discovery of the Antarctic ozone hole in 1985. After negotiation of an international treaty (the Montreal Protocol), CFC production was sharply limited beginning in 1987 and phased out completely by 1996.

On August 2, 2003, scientists announced that the depletion of the ozone layer may be slowing down due to the international ban on CFCs.[4] Three satellites and three ground stations confirmed that the upper atmosphere ozone depletion rate has slowed down significantly during the past decade. The study was organized by the American Geophysical Union. Some breakdown can be expected to continue due to CFCs used by nations which have not banned them, and due to gases which are already in the stratosphere. CFCs have very long atmospheric lifetimes, ranging from 50 to over 100 years, so the final recovery of the ozone layer is expected to require several lifetimes.

Distribution Of Ozone In The Stratosphere

November 14, 2008

The thickness of the ozone layer—that is, the total amount of ozone in a column overhead—varies by a large factor worldwide, being in general smaller near the equator and larger as one moves towards the poles. It also varies with season, being in general thicker during the spring and thinner during the autumn in the northern hemisphere. The reasons for this latitude and seasonal dependence are complicated, involving atmospheric circulation patterns as well as solar intensity.

Since stratospheric ozone is produced by solar UV radiation, one might expect to find the highest ozone levels over the tropics and the lowest over polar regions. The same argument would lead one to expect the highest ozone levels in the summer and the lowest in the winter. The observed behavior is very different: most of the ozone is found in the mid-to-high latitudes of the northern and southern hemispheres, and the highest levels are found in the spring, not summer, and the lowest in the autumn, not winter in the northern hemisphere. During winter, the ozone layer actually increases in depth. This puzzle is explained by the prevailing stratospheric wind patterns, known as the Brewer-Dobson circulation. While most of the ozone is indeed created over the tropics, the stratospheric circulation then transports it poleward and downward to the lower stratosphere of the high latitudes. However in the southern hemisphere, owing to the ozone hole phenomenon, the lowest amounts of column ozone found anywhere in the world are over the Antarctic in the southern spring period of September and October.

The ozone layer is higher in altitude in the tropics, and lower in altitude in the extratropics, especially in the polar regions. This altitude variation of ozone results from the slow circulation that lifts the ozone-poor air out of the troposphere into the stratosphere. As this air slowly rises in the tropics, ozone is produced by the overhead sun which photolyzes oxygen molecules. As this slow circulation bends towards the mid-latitudes, it carries the ozone-rich air from the tropical middle stratosphere to the mid-and-high latitudes lower stratosphere. The high ozone concentrations at high latitudes are due to the accumulation of ozone at lower altitudes.

The Brewer-Dobson circulation moves very slowly. The time needed to lift an air parcel from the tropical tropopause near 16 km (50,000 ft) to 20 km is about 4-5 months (about 30 feet (9.1 m) per day). Even though ozone in the lower tropical stratosphere is produced at a very slow rate, the lifting circulation is so slow that ozone can build up to relatively high levels by the time it reaches 26 km.

Ultraviolet Light And Ozone

November 14, 2008

Although the concentration of the ozone in the ozone layer is very small, it is vitally important to life because it absorbs biologically harmful ultraviolet (UV) radiation emitted from the Sun. UV radiation is divided into three categories, based on its wavelength; these are referred to as UV-A (400-315 nm), UV-B (315-280 nm), and UV-C (280-100 nm). UV-C, which would be very harmful to humans, is entirely screened out by ozone at around 35 km altitude. UV-B radiation can be harmful to the skin and is the main cause of sunburn; excessive exposure can also cause genetic damage, as a result problems such as skin cancer. The ozone layer is very effective at screening out UV-B; for radiation with a wavelength of 290 nm, the intensity at Earth’s surface is 350 billion times weaker than at the top of the atmosphere. Nevertheless, some UV-B reaches the surface. Most UV-A reaches the surface; this radiation is significantly less harmful, although it can potentially cause genetic damage.

Origin Of Ozone

November 14, 2008

The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930. Ozone in the earth’s stratosphere is created by ultraviolet light striking oxygen molecules containing two oxygen atoms (O2), splitting them into individual oxygen atoms (atomic oxygen); the atomic oxygen then combines with unbroken O2 to create ozone, O3. The ozone molecule is also unstable (although, in the stratosphere, long-lived) and when ultraviolet light hits ozone it splits into a molecule of O2 and an atom of atomic oxygen, a continuing process called the ozone-oxygen cycle, thus creating an ozone layer in the stratosphere, the region from about 10 to 50 km (32,000 to 164,000 feet) above Earth’s surface. About 90% of the ozone in our atmosphere is contained in the stratosphere. Ozone concentrations are greatest between about 20 and 40 km, where they range from about 2 to 8 parts per million. If all of the ozone were compressed to the pressure of the air at sea level, it would be only a few millimeters thick.

Ozone Layer

November 14, 2008

The ozone layer is a layer in Earth’s atmosphere which contains relatively high concentrations of ozone (O3). This layer absorbs 93-99% of the sun’s high frequency ultraviolet light, which is potentially damaging to life on earth.[1] Over 91% of ozone in earth’s atmosphere is present here.[1] “Relatively high” means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 10 km to 50 km above Earth’s surface, though the thickness varies seasonally and geographically.[2] The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations which continues to operate today(2008). The “Dobson unit”, a convenient measure of the total amount of ozone in a column overhead, is named in his honor.

Titanic Ship

November 13, 2008

Titanic was one the greatest ship built in twentieth century. The ship was supposed to be unsinkable but some things are beyond the reach of human intelligence and cannot predict the future.

This was the first voyage of Titanic. Hundreds of passengers were in enthusiasm and ready to enjoy the long journey. The Titanic ship was considered to be strong enough and built on the latest technologies and was equipped with all sorts of emergency facilities. People from different countries like Iran, France and Italy were on board. The Captain of the Titanic was Edward Smith. He was a Jesuit and had served for J.P. Morgan. The powerful ship began its voyage from south England. The ship was supposed to pass through Atlantic Ocean on the way of its journey. Captain Smith was quite experienced person and had traveled the North Atlantic for 26 years. There were very few captains like him who had the experience of travelling in cold waters. He knew exactly where the icebergs were.

The journey of Titanic was planned to commence March 1912 but the construction ship could not be completed within specified time. Also the fuel required that is coal was not easily available because of strike the supply of coal wasn’t permitted. More than required quantity of fuel was then collected from other ships in order to ensure that lack of fuel supply wasn’t a problem for completion of journey. This fuel later added to the agony of disaster.

Titanic journey before disaster:
Titanic was registered in Liverpool. The historic journey began her maiden voyage from Southampton. It was Wednesday and cool morning of spring. Many of the passengers from other ships were transferred in this boat. The first halt she took was at Cherbourg, France. To attract the passengers from this part it was anchored a mile from shore.

The ship headed for its next halt in the evening. By after noon Titanic reached at Queenstown in Ireland. It was 11th April. Father Francis Brown, the most respected Jesuit priest stepped out at this place. He survived from being a part of the dreadful journey. He might have not even thought that the photographs taken by him will turn out to be the memories of this beautiful ship.

Titanic’s interior Decoration:
Though the ship was far in the midst of ocean far away from luxury out at home nothing was left to make the passengers live lavishing lifestyle. All sorts of entertainment things were available. Whole ship had abundant supply of electricity. The ship was equipped with four 400 kilowatt electrical generators. The passengers were given separate rooms and were able to use electric lamps and heaters. Many were experiencing the high level facilities for the first time. All variety food and drinks were available on the deck. There were many indoor games available. For those who had the practice of daily exercise gymnasium was present. Lifts were there for moving from one place to another. The huge storage of food was done and kept in appropriate refrigerating conditions. To protect from cold rooms were kept warm through heaters. Fans were provided at many places to take care of ventilation. Communication with the people thousands mile apart wasn’t a matter of worry telephones were also provided. The radios of this ship had range of four hundred miles during day time. Some of the recordings of radio operators were recorded before the ship sunk.

History of rocket >90s

November 10, 2008

The 1990s brought major changes at JPL. In 1991, Lew Allen retired and Edward C. Stone, the Voyager project scientist, became JPL’s director. The following year, Daniel S. Goldin became NASA administrator. Goldin hated the slow, expensive and not necessarily reliable approach of the past two decades, and set out to reform all of NASA. His favorite targets of ridicule were the failed Mars Observer and a Saturn mission, Cassini/Huygens, which had been recently approved and was expected to cost $3.3 billion. His goal was to reduce the cost of planetary missions all the way down to $150 million. He challenged JPL to adapt itself to his new “faster, better, cheaper” techniques in a 1992 speech.

The result was the most vibrant and exciting period of planetary exploration since the 1960s, and a great deal of pain as Ed Stone and the rest of the lab’s staff tried to find ways to meet Goldin’s challenge. The era ended abruptly in 2000, after JPL lost two more spacecraft, both at Mars.

The Faster, Better, Cheaper Challenge

Goldin, who had been an executive at aerospace giant TRW, thought that by using new management techniques, new technologies and accepting more risk, NASA could dramatically reduce the cost of missions. More could be done without more money.

Doing more with less was important because a major political focus of the Clinton administration was achieving a balanced budget. NASA’s budget shrank 18 percent between 1992 and 1999. Without finding ways to cut costs substantially, JPL faced extinction. The NASA budget would not support enough Cassini-scale missions to keep the lab operating.

In a speech at JPL on May 28, 1992, Goldin laid all this out for JPL’s staff. “We need to stretch ourselves,” he said. “Be bold — take risks. [A] project that’s 20 for 20 isn’t successful. It’s proof that we’re playing it too safe. If the gain is great, risk is warranted. Failure is OK, as long as it’s on a project that’s pushing the frontiers of technology.”

History Of Rocket 80s

November 10, 2008

In early 1981, the White House Office of Management and Budget demanded deep cuts to NASA’s budget. In response, NASA administrator James M. Beggs proposed terminating the nation’s planetary exploration program. This would, he had pointed out to White House officials, “make the Jet Propulsion Laboratory in California surplus to our needs.”

JPL Director Murray organized a political campaign in Washington to save JPL and the planetary program. Murray and allies in Congress succeeded in salvaging the Galileo mission to Jupiter. Acknowledging that this was not enough to preserve JPL for long, Murray also gained Caltech and NASA approval to begin doing Defense Department-sponsored research and development.

After Murray retired in 1982, his successor, Lew Allen, gained three missions from the slowly reviving NASA science program. Two were planetary missions, Mars Observer and Magellan to Venus, and the third an Earth science mission, Topex/Poseidon. Somewhat ironically, JPL reached its historic peak employment in 1987, with more than 7,000 employees and contractors. This was also the year military funding for JPL reached its peak, 35 percent of the lab’s total budget.

Finally, JPL became a significant builder of scientific instruments during the decade. In 1986, NASA held a competition to develop instruments for a new “Mission to Planet Earth” that the lab’s scientists did very well in.

Early History First Rocket Test

November 10, 2008

he Jet Propulsion Laboratory’s history reaches back to the tumultuous years leading up to World War II. Rockets were perceived as devices of fantasy, seen only in movie serials and comic strips like Buck Rogers and Flash Gordon. Despite rocket pioneer Robert Goddard’s successful development of early rockets, he was publicly ridiculed for his work. But in the fall of 1936, a group of enterprising young men in Pasadena, Calif., decided to risk their reputations and give engineering substance to rocket fantasy.

The “rocket boys” were an unusual bunch. Frank Malina was studying aerodynamics at Caltech’s Guggenheim Aeronautical Laboratory, known as GALCIT. Jack Parsons was a self-taught chemist, and Ed Forman was an excellent mechanic. They scraped together cheap engine parts, and on Oct. 31, 1936, drove to an isolated area called the Arroyo Seco at the foot of the San Gabriel Mountains.

Four times that day they tried to test fire their small rocket motor. On the last attempt, they accidentally set fire to their oxygen line, which whipped around shooting fire! These were the first rocket experiments in the history of JPL. They tried again on Nov. 15, 1936, and their experiment finally worked.

‘Madagascar’ roars with $63.5 million weekend

November 10, 2008

LOS ANGELES (AP) — Families herded into movie theaters for another trek with stranded zoo animals as the animated sequel “Madagascar: Escape 2 Africa” led the weekend with a $63.5 million debut, according to studio estimates Sunday.

The haul for the DreamWorks Animation comedy far surpassed the $47.2 million debut for “Madagascar” over Memorial Day weekend in 2005. Its three-day total also beat the $61 million gross the first movie took in over that full four-day holiday weekend.

“It just shows people seem happy to escape to the movies and have a good laugh,” said Anne Globe, head of marketing for DreamWorks Animation.

While parents with children were the bulk of the audience, “Madagascar” also drew teens and adults on their own, who made up half the audience on Friday and one-third on Saturday, Globe said.

Premiering in second place with $19.3 million was the Universal Pictures comedy “Role Models,” starring Seann William Scott and Paul Rudd as immature adults sentenced to community service as mentors for two misfit youths.

The weekend’s other new wide release, the Weinstein Co. music comedy “Soul Men,” opened weakly with $5.6 million, despite the lure of Samuel L. Jackson and his late co-stars, Bernie Mac and Isaac Hayes, who died last summer. Jackson and Mac play an estranged singing team on a reunion road trip to a memorial concert.