الاسبانية لابد
04-03-2007, 04:09 PM
ارججووووووووووووووووووووووووووووووووووووووووووووووووووووووووووو كم :'(
ابي بحث حق انج 102 :'(
:'( :'( :'( :'( :'( :'( :'( :'(
لوسمحتو ابي الرد ابسرعة :'( :'(
اتمنى ان تسعدوني :'( :'( :'(
بحر الرفاع
04-03-2007, 06:21 PM
ارججووووووووووووووووووووووووووووووووووووووووووووووووووووووووووو كم :'(
ابي بحث حق انج 102 :'(
:'( :'( :'( :'( :'( :'( :'( :'(
لوسمحتو ابي الرد ابسرعة :'( :'(
اتمنى ان تسعدوني :'( :'( :'(
هذي البجث اختي واتمنى يعجبج
زعفرانه
04-03-2007, 08:02 PM
Venus
I INTRODUCTION
interactivity
Orbit
Venus (planet), one of the planets in the solar system, the second in distance from the Sun. Except for the Sun and the Moon, Venus is the brightest object in the sky. The planet is called the morning star when it appears in the east at sunrise, and the evening star when it is in the west at sunset. In ancient times the evening star was called Hesperus and the morning star Phosphorus or Lucifer. Because of the distances of the orbits of Venus and Earth from the Sun, Venus is never visible more than three hours before sunrise or three hours after sunset.
Venus Venus is the brightest object in our sky, after the sun and moon. Swirling clouds of sulfur and sulfuric acid obscure Venus’s surface and inhibited study of the planet from Earth until technology permitted space vehicles, outfitted with probes, to visit it. These probes determined that Venus is the hottest of the planets, with a surface temperature of about 460° C (about 860° F). Scientists believe that a greenhouse effect causes the extreme temperature, hypothesizing that the planet’s thick clouds and dense atmosphere trap energy from the sun.Photo Researchers, Inc./NASA/Science Source
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When viewed through a telescope, the planet exhibits phases like the Moon. Maximum brilliance (a stellar magnitude of -4.4, 15 times as bright as the brightest star) is seen in the crescent phase when Venus is closer to Earth. Venus’s full phase appears smaller and dimmer because it occurs when the planet is on the far side of the Sun from Earth. The phases and positions of Venus in the sky repeat every 1.6 years (see Time; Year). Transits of Venus (when the planet moves across the face of the Sun as seen from Earth) are rare, occurring in pairs at intervals of a little more than a century. The next two transits will be in 2004 and 2012.
II EXPLORATION
Magellan Spacecraft The Magellan probe to Venus mapped almost all of the planet’s surface and provided scientists with a vast amount of data. The probe is shown here in the cargo bay of the space shuttle Atlantis before the shuttle’s 1989 launch. Magellan reached Venus in 1990.NASA
Venus's complete cloud cover and deep atmosphere make it difficult to study from Earth. Most knowledge of the planet has been obtained through the use of space vehicles, particularly those carrying probes that descend through the atmosphere. The first flyby was that of Mariner 2, launched by the United States in 1962, followed by Mariner 5 in 1967 and Mariner 10 in 1974. The former Union of Soviet Socialist Republics developed several entry probes, some combined with flybys or orbiters: Venera 4 and 5 (1967), 6 (1969), 7 (1970), 8 (1972), 9 and 10 (1975), 11 and 12 (1978), 13 and 14 (1981), and 15 and 16 (1983); Vega 1 and 2, sent toward Halley's comet in 1984, also flew by Venus and released descent capsules. Several of these probes successfully reached the planet's surface. The United States sent two Pioneer Venus missions in 1978. Pioneer Venus 2 sent four probes to the surface, while the remaining craft explored the upper atmosphere. Pioneer Venus 1, an orbiter, measured the upper atmosphere for 14 years. The Magellan probe, launched toward Venus in 1989, transmitted radar images of the planet from 1990 to 1994.
III ATMOSPHERE
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The atmosphere of the planet consists of 97 percent carbon dioxide (CO2) and is so thick that the surface pressure is 96 bars (compared with 1 bar on Earth). The surface temperature on Venus varies little from place to place and is extremely hot, about 462°C (736 K/864°F). The high surface temperature is explained by an intense greenhouse effect. Even though only a small percentage of the solar energy that falls on Venus reaches the surface, the planet stays hot because the thick atmosphere prevents the energy from escaping.
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Venus (planet)
That nearly all of Venus's atmosphere is CO2 is not as strange as it might seem; in fact, the crust of Earth contains almost as much CO2 chemically bound in the form of limestone. About 3 percent of the Venusian atmosphere is nitrogen gas (N2). By contrast, 78 percent of Earth's atmosphere is nitrogen. Water and water vapor are extremely rare on Venus. Many scientists argue that Venus, being closer to the Sun, was subjected to a so-called runaway greenhouse effect, which caused any oceans to evaporate into the atmosphere. The hydrogen atoms of the water molecules could have been lost to space and the oxygen atoms to the crust. Another possibility is that Venus had very little water to begin with.
Cloud particles on Venus mostly consist of concentrated sulfuric acid. Earth’s atmosphere also contains a very thin haze of sulfuric acid particles in the stratosphere. On Earth, however, sulfuric acid does not build up because rain carries it down to react with surface materials. On Venus the acid evaporates at the cloud base, which lies about 50 km (31 mi) above the surface, and so remains in the atmosphere. The upper parts of the clouds, visible from Earth and from Pioneer Venus 1, extend as haze 70 to 80 km (44 to 50 mi) above the surface. The clouds contain a pale yellow impurity, better detected at near-ultraviolet wavelengths. Variations in the sulfur dioxide content of the atmosphere may indicate active volcanism on the planet.
Certain cloud patterns and weather features that can be discerned in the cloud tops give some information about wind motion in the atmosphere. The upper-level winds circle the planet at 360 km/h (225 mph). These winds cover the planet completely, blowing toward the east at virtually every latitude from equator to pole. The motions of descending probes, however, have shown that the bulk of Venus's tremendously dense atmosphere, closer to the planet's surface, is almost stagnant. From the surface up to 10 km (6 mi) altitude, wind speeds are only about 3 to 18 km/h (2 to 11 mph). The high-*****sss winds probably result from the transfer of momentum from Venus's slow-moving, massive lower atmosphere to higher altitudes where the atmosphere is less massive, so that the same momentum results in a much higher velocity.
The upper atmosphere and ionosphere were studied in great detail by Pioneer Venus 1, which passed through them once each day. On Earth this region is very hot; on Venus it is not, even though Venus is closer to the Sun. Surprisingly, on the night side of Venus the upper atmosphere is extremely cold. (Day-side temperatures are 40°C/104°F, compared to night-side temperatures of -170°C/-274°F.) Scientists believe that strong winds blow from the day side toward the near vacuum that is caused by the low temperatures on the night side. Such winds would carry along light gases, such as hydrogen and helium, which are concentrated in a night-side “bulge.”
In contrast to the very large antenna needed for Earth-based radar mapping of Venus, a modest instrument on Pioneer Venus 1 was able to conduct a nearly global survey. Combined with data from the Soviet probes, the Magellan orbiter, and Earth-based radar, the survey shows that the surface of Venus is primarily a rolling plain interrupted by two continent-sized highland areas, which have been named Ishtar Terra and Aphrodite Terra after two manifestations of the goddess Venus. Aphrodite Terra, although not as high as Ishtar Terra, extends nearly halfway around the equatorial region; it occupies the planet's far side as viewed from Earth at closest approach.
The more powerful radar aboard the Magellan spacecraft has revealed huge volcanoes, large solidified lava flows, and a large array of meteorite craters. The largest impact crater is almost 300 km (190 mi) across—the smallest about 5 km (3 mi). Although the probe's radar could resolve even smaller craters, if any were present, Venus's dense atmosphere apparently prevents smaller meteorites from impacting the surface of the planet. It is believed that all craters older than about 500 million years have been obliterated, while the more recent ones show little sign of modification.
The global survey and other probes have also revealed evidence that a great deal of tectonic activity has taken place on Venus, at least in the past. Such evidence includes ridges, canyons, a troughlike depression that extends across 1400 km (870 mi) of the surface, and a gigantic volcanic cone whose base is more than 700 km (435 mi) wide. The Soviet probes sent back photographs of the areas in which they set down, and also measured the natural radioactivity of the rocks. The radioactivity resembles that of granite and strongly suggests that the material of Venus is differentiated, or chemically separated, by volcanic activity. Angular rocks that are visible in the Soviet pictures also suggest the existence of geologic activity that would counteract the forces of erosion
زعفرانه
04-03-2007, 08:03 PM
Sky Surfing
The Most Extreme of the Extreme Sports
History of sky diving
A relatively new sport, sky surfing obviously developed from sky diving. Skydivers, whose focus has traditionally aligned within the discipline of formation flying, first began experimenting with boards in freefall about 15 years ago. This initial maneuver of lying down in flight was replaced with standing up on a board after a seven-year lull. Once this maneuver was perfected, athletes have become more and more daring and their flights more sophisticated. Sky surfing has been with the X Games since the game's conception in 1985.
Description of the sport
A cross between skateboarding and sky diving, sky surfing is a sport in which you jump out of an aircraft with a board strapped to your feet. You use the board during free fall to execute acrobatics by working against the slipstream, so you really are surfing, but on air rather than on water. Some of these acrobatics look spectacular, but they can be extremely dangerous if they're not done just right, because you can get into a spin that's impossible to recover from. For the above reasons, sky surfing is regarded as just about the most dangerous -- but also the most exhilarating of extreme sports.
Did you know?
Did you know that in most competitions today sky surfers compete in pairs, with one member of the duo filming the other as he executes a series of incredible aerial maneuvers? While spectators cannot see any of the action, the sport obviously offers some of the exciting sports footage and is a natural for filming.
On Ollies and the Origins of Skateboarding
In 1978 a young man revolutionized skateboarding. While riding, he pushed downward with his back foot, causing the front of the board to rise. He then jumped with the board, causing both the board and himself to lift into the air about five inches. This move has come to be known as the Ollie, after Alan "Ollie" Gelfand.
Skateboarding really is nothing more than riding a wheeled board as a surfer does a wave. It's no surprise then that its origins date back to sunny California in the 1950s, when some surfer dudes decided that they wanted to practice their moves on land. All over California, surfers and teenagers began constructing their own "land surfboards" by attaching roller wheel skates to wooden crates. A craze was born, which lasted until the mid 60s. An inferior product, clay wheels that did not grip the road well and numerous injuries, lead to decreased interest.
Then, in the early 80s, a new design that used polyurethane wheels and a wider board made the sport exciting again. Skateboarders could finally launch themselves off the ground and perform twists and turns, half pipes and ollies. A new generation of skateboarders emerged, a subculture of young kids who perfected their moves on the street, on handrails and cement ramps in parks. By the time the ESPN Extreme Games gave the sport even more visibility, Tony Hawk and Mark Gonzales were creating a new group of believers.
Women on...Board
Although the vast majority of skateboarders are male, women are gaining ground and creating their own role models for young girls to emulate. One of the top skateboarders in the world is Cara-Beth Burnside, a woman who was also a member of the 1998 U.S. Olympic snowboarding team. Amy Caron, Vanessa Torres, Monica Shaw, Jaime Reyes are some of the new names on the scene. In 1990, Patty Segovia organized the first All Girl Skate Jam -- a series of skating competitions in Reno, Nevada, in an effort to recognize female skateboarding. Since then, there have been 15 AGSJ’s held nationally and internationally. In August 2002, ESPN broadcast female skateboarding as part of its Philadelphia X-Games.
Despite the gains however, there is still resistance by some men over females skating in on their turf. The derogatory term "Skating Betty" exists to describe girls who want to meet cute guys, not skateboard seriously. Unfortunately for the cute guys, that's rarely the case with most girls who practice the sport.
Skateboarding requires patience and practice; attempting a move over and over again until you get it right. And until you do, bruises, sprains and maybe a broken leg or arm is part of the process. Despite the risks involved, young girls are flaunting their creativity and their success at defying gravity, as they lay down their tricks. Now who has time to flirt when there's so much to learn
الاسبانية لابد
05-03-2007, 03:25 PM
يسلموووووووووووووووووووون على الردود بس لوسمحتي ..................عندج عن : life in the futur