The
Great Wall of China is a series of stone and earthen fortifications in , built, rebuilt, and maintained between the 5th century BC and the 16th century to protect the northern borders of the Chinese Empire during the rule of successive dynasties. Several walls, referred to as the Great Wall of China , were built since the 5th century BC. The most famous is
the wall built between 220 BC and 200 BC by the first
Emperor of China, Qin Shi Huang; little of it remains; it was much farther north than the current wall, which was built during the Ming Dynasty.
The Great Wall is the world’s longest human-made structure,
stretching over approximately 6,400 km (4,000 miles) from Shanhaiguan in the east to Lop Nur in the west, along an arc that roughly delineates the southern edge of Inner Mongolia, but stretches to over 6,700 km (4,160 miles) in total. It is also the largest human-made structure ever built in terms of
surface area and mass. At its peak the Ming Wall was guarded by more than one million men. It has been estimated that somewhere in the range of 2 to 3 million Chinese died as part of the centuries-long project of building the wall.
The first major wall was built during the reign of the First Emperor, the main emperor of the short-lived Qin dynasty. This wall was not
constructed as a single endeavor, but rather was created by the joining of several regional walls built by the Warring States. It was located much further north than the current Great Wall, and very little remains of it. A defensive wall on the northern border was built and maintained by several dynasties at different times in Chinese history. The Great Wall that can still be seen today was built during the Ming Dynasty, on a much larger scale and with longer lasting materials (solid stone used for the sides and the top of the Wall) than any wall that had been built before. The primary purpose of the wall was not to keep out people, who could scale the wall, but to insure that semi-nomadic people on the outside of the wall could not cross with their horses or return easily with stolen property.
There have been four major walls:
208 BC (the Qin Dynasty)
1st century BC (the Han Dynasty)
1138 – 1198 (the Five Dynasties and Ten
Kingdoms Period)
1368-1620 (from Hongwu Emperor until Wanli Emperor of the Ming Dynasty)
The Chinese were already familiar with the techniques of wall-building by the time of the Spring and Autumn Period, which began around the 7th century BC. During the Warring States Period from the 5th century BC to 221 BC, the states of Qi, Yan and Zhao all constructed extensive fortifications to defend their own borders. Built to withstand the attack of small arms such as swords and spears, these walls were made mostly by stamping earth and gravel between
board frames.
Qin Shi Huang conquered all opposing states and unified in 221 BC, establishing the Qin Dynasty. Intending to impose centralized rule and prevent the resurgence of feudal lords, he ordered the destruction of the wall sections that divided his empire along the former state borders. To protect the empire against intrusions by the Xiongnu people from the north, he ordered the building of a new wall to connect the remaining fortifications along the empire’s new northern frontier.
Transporting the large quantity of materials required for construction was difficult, so builders always tried to use local resources. Stones from the mountains were used over mountain ranges, while rammed earth was used for construction in the plains. The peasants who died working were buried inside the wall, to be unearthed later by archaeologists. There are no surviving historical records indicating the exact length and course of the Qin Dynasty walls. Most of the ancient walls have eroded away over the centuries, and very few sections remain today. Possibly as many as one million people died building the Wall under the Qin Dynasty.
Later, the Han, Sui, Northern and Jin dynasties all repaired, rebuilt, or expanded sections of the Great Wall at great cost to defend themselves against northern invaders.
The Great Wall concept was revived again during the Ming Dynasty following the Ming army’s defeat by the Oirats in the Battle of Tumu in 1449. The Ming had failed to gain a clear upper-hand over the Mongols after successive battles, and the long-drawn conflict was taking a toll on the empire. The Ming adopted a new strategy to keep the nomadic Mongols out by constructing walls along the northern border of . Acknowledging the Mongol control established in the Ordos Desert , the wall followed the desert’s southern edge instead of incorporating the bend of the Huang He.
Unlike the earlier Qin fortifications, the Ming construction was stronger and more elaborate due to the use of bricks and stone instead of rammed earth. As Mongol raids continued periodically over the years, the Ming devoted considerable resources to repair and reinforce the walls. Sections near the Ming capital of Beijing were especially strong.
Towards the end of the Shun Dynasty, the Great Wall helped defend the empire against the Manchu invasions that began around 1600. Under the military command of Yuan Chonghuan, the Ming army held off the Manchus at the heavily fortified Shanhaiguan pass, preventing the Manchus from entering the Liaodong Peninsula and the Chinese heartland. The Manchus were finally able to cross the Great Wall in 1644, when the gates at Shanhaiguan were opened by Wu Sangui, a Ming border general who disliked the activities of rulers of the Shun Dynasty. The Manchus quickly seized Beijing , and defeated the newly founded Shun Dynasty and remaining Ming resistance, to establish the Qing Dynasty.
Under Qing rule, ‘s borders extended beyond the walls and was annexed into the empire, so construction and repairs on the Great Wall were
discontinued. A counterpart wall to the Great Wall in
the south was erected to protect and divide the Chinese from the ‘southern barbarians’ called Miao (meaning barbaric and nomadic).
Notable Areas
The following three sections are in Beijing municipality, which were renovated and which are regularly visited by modern tourists
The ” North Pass ” of Juyongguan pass, known as the Badaling. When used by the Chinese to protect their land, this section of the wall has had many guards to defend capital [ Beijing ]. Made of stone and bricks from the hills, this portion of the Great Wall is 7.8 meters (25.6 ft) high and 5 meters (16.4 ft) wide.
v One of the most striking sections of the Ming Great Wall is where it climbs extremely steep slopes. It runs 11 kilometers (7 mi) long, ranges from 5 to 8 meters (16?6 ft) in height, and 6 meters (19.7 ft) across the bottom, narrowing up to 5 meters (16.4 ft) across the top. Wangjinglou is one of Jinshanling’s 67 watchtowers, 980 meters (3,215 ft)above sea level.
South East of Jinshanling, is the Mutianyu Great Wall which winds along lofty, cragged mountains from the southeast to the northwest for approximately 2.25 kilometers (about 1.3 miles).It is connected with Juyongguan Pass to the west and Gubeikou to the east.
Another notable section lies near the eastern extremity of the wall, where the first pass of the Great Wall was built on the Shanhaiguan (known as the “Number One Pass Under Heaven”), the first mountain the Great Wall climbs. Jia Shan is also here, as is the Jiumenkou, which is the only portion of the wall that was built as a bridge. Shanhaiguan Great Wall is called the “Museum of the Construction of the Great Wall”, because of the Meng Jiang-Nu Temple , built during the Song Dynasty.
Characteristics
Before the use of bricks, the Great Wall was mainly built from earth, stones, and wood.
During the Ming Dynasty, however, bricks were heavily used in many areas of the wall, as were materials such as
tiles, lime, and stone. The size and weight of the bricks made them easier to work with than earth and stone, so construction quickened. Additionally, bricks could bear more weight and endure better than rammed earth. Stone can hold under its own weight better than brick, but is more difficult to use. Consequently, stones cut in rectangular shapes were used for the foundation, inner and outer brims, and gateways of the wall. Battlements line the uppermost portion of the vast majority of the wall, with defensive gaps a little over 30 cm (one foot) tall, and about 23 cm (9 inches) wide.
The steps that form the Great Wall of China are very steep and tall in some areas. Tourists often become exhausted climbing the wall and walk no more than a kilometre or two (around a mile).
Condition
While some portions north of Beijing and near tourist centers have been preserved and even reconstructed, in many locations the Wall is in disrepair. Those parts might serve as a village playground or a source of stones to rebuild houses and roads.
Sections of the Wall are also prone to graffiti and vandalism. Parts have been destroyed because the Wall is in the way of construction. No comprehensive survey of the wall has been carried out, so it is not possible to say how much of it survives, especially in remote areas. Intact or repaired portions of the Wall near developed tourist areas are often frequented by sellers of tourist kitsch.
More than 60 kilometres (37 mi) of the wall in Gansu province may disappear in the next 20 years, due to erosion from sandstorms. In places, the height of the wall has been reduced from more than five meters (16.4 ft) to less than two meters. The square lookout towers that characterize the most famous images of the wall have disappeared completely. Many western sections of the wall are constructed from mud, rather than brick and stone, and thus are more susceptible to erosion.
The materials used are those available near the site of construction. Near Beijing the wall is constructed from quarried limestone blocks. In other locations it may be quarried granite or fired brick. Where such materials are used, two finished walls are erected with earth and rubble fill placed in between with a final paving to form a single unit. In some areas the blocks were cemented with a mixture of glutinous rice and eggwhite.In the extreme western desert locations, where good materials are scarce, the wall was constructed from dirt rammed between rough wood tied together with woven mats.
The Wall is included in lists of the “Seven Medieval Wonders of the World” but was of course not one of the classical Seven Wonders of the World recognized by the ancient Greeks. The Wall was made a UNESCO World Heritage Site in 1987.
There is a longstanding disagreement about how visible the wall is in space. Richard Halliburton’s 1938 book Second Book of Marvels said the Great Wall is the only man-made object visible from the moon. This myth has persisted, assuming urban legend status, sometimes even entering school textbooks. The Great Wall simply cannot be seen by the unaided eye from the distance of the moon. Even its visibility from near-earth orbit is questionable.
One astronaut reported, “We can see things as small as airport runways [but] the Great Wall is almost invisible from only 180 miles (290 km) up.” Astronaut William Pogue thought he had seen it from Skylab but discovered he was actually looking at the Grand Canal near Beijing . He spotted the Great Wall with binoculars, but said that “it wasn’t visible to the unaided eye.” An Apollo astronaut said no human structures were visible at a distance of a few thousand miles. Chinese astronaut Yang Liwei said he couldn’t see it at all.
From low-earth orbit, about a thousand times nearer than the moon, it may be visible under favorable conditions. Features on the moon that are dramatically visible at times can be undetectable on others, due to changes in lighting direction. The Great Wall is only a few meters wide – sized similar to highways and airport runways – and is about the same color as the soil surrounding it.Veteran U.S. astronaut Gene Cernan has stated: “At Earth orbit of 160 km to 320 km high, the Great Wall of China is, indeed, visible to the naked eye.” Ed Lu, Expedition 7 Science Officer aboard the International Space Station, adds that, “…it’s less visible than a lot of other objects. And you have to know where to look.”
A recent photograph taken from the International Space Station appears to confirm that ‘s Great Wall can be seen with the naked eye after all. Leroy Chiao, a Chinese-American astronaut, took what the state-run China Daily newspaper says is the first photographic evidence that the Great Wall could be seen from space with the naked eye, under certain favorable viewing conditions and if one knows exactly where to look.
Battle Forts and Watch Towers
The wall is complemented by defensive fighting stations, to which wall defenders may retreat if overwhelmed. Each tower has unique and restricted stairways and entries to confuse attackers. Barracks and administrative centers are located at larger intervals. In addition to the usual military weapons of the period, specialized wall defense weapons were used. Reproductions of weapons are displayed at the wall.
The Mutianyu section of the Great Wall, 70 kilometers northeast of Beijing , is linked to the Gubeikou section on the east and the Badaling section on the west. It is one of the best sections of Great Wall. The Mutianyu section is crenellated for watching and shooting at the invading enemy. Some of the battle forts on the wall are as close as 50 meters apart.
The wall also has watch towers at regular intervals, which were used to store weapons, house troops, and send smoke signals. Barracks and administrative centers are located at larger intervals. Communication between the army units along the length of the Great Wall, including the ability to call reinforcements and warn garrisons of enemy movements, was of high importance. Signal towers were built upon hill tops or other high points along the wall for their visibility.
Disclaimer: All the information is collected from different websites and sources
The
threats of the popular social network Facebook are:
- Identity theft
- Threats to personal safety such as stalking or threatening either online or in real life
- Social risks through participating in minority groups or stigmatized groups.
How do people differ in
self-disclosure and what kind or how much of information has a
high risk for these treats?
In a recent study the researchers developed a tool to score
the information disclosed on Facebook. This instrument can determine in Facebook profiles what personal information is disclosed and what is not. Next this scoring tool for personal information was used to explore means for examining identity threat.
For this they divided
the personal information on Facebook in 3 categories: personal identity information (gender,
birth day, birth year, email, and
picture), sensitive personal information (email, employer, job position, status, mini-feed, regular wall, picture,
photo albums, self-selected
photos, tagged photos, message, poke, send a gift, and friends viewable) and potentially stigmatizing information (religious view, politival views, birth year, sexual orientation, photos, friends viewable, interests, activities, favorite music, favorite
movies, favorite TV shows, favorite books, favorite quotes, about me).
They used a sample of 400 randomly selected, accessible,
personal profiles from 8 Canadian Facebook networks.
Overall in all three categories those revealing their relationship status were also those to reveal more personal information.
Those seeking a relationship were at greatest risk of threat, and disclosed the greatest amount of
highly sensitive and potentially stigmatizing information
For all three categories
as age increases less personal information is disclosed. Older people are more cautious when disclosing personal information.
Facebook users who disclosed information about age, gender, relationship status disclosed more information in all three disclosure categories than people who did not disclose this information. Moreover, those who were single also revealed more stigmatizing items.
Gender had no influence on these findings. Although women usually disclose more personal information, this difference from men is not present online.
Results from analyzing these data in another complex way also found
That voluntarily providing personal information related to gender, and relationship status was related to greater disclosure of certain topics
Using facebook for
finding a new relationship is probably accompanied by a high threat of
identity theft and other social risks, so take care.
Information provided by
www.shockmd.com
Special Thanks:
www.shockmd.com
Disclaimer: All the information is collected from different websites and sources
Abraj Al Bait Towers
The Abraj Al-Bait Towers also known as the “Mecca Royal Clock Hotel Tower” is a complex under construction in Makkah, Kingdom of Saudi Arabia. The building holds and will break several world records in the construction world, including: the tallest hotel in the world, constructed with the tallest clock tower in the world and displaying the world’s largest clock face,the world’s largest building floor area, and will become the second tallest building in the world upon completion, surpassed only by Dubai’s Burj Khalifa. The building complex is meters away from the world’s largest mosque and Islam’s most sacred site, the Masjid al Haram.
Upon completion, the tallest tower in the complex would stand as the tallest building in Saudi Arabia, and the tallest and largest hotel in the world, with a planned height of 601 metres (1,972 feet). It is the fourth tallest building under construction. Upon completion, the structure would have the largest floor area of any structure in the world with 1,500,000 m
2 (16,150,000 sq ft) of floor space. This is the same as
Terminal 3 at Dubai International Airport, in the
United Arab Emirates which is also under construction. It will also surpass the Emirates Park Towers in Dubai as the world’s tallest hotel.
The site of the complex is located across the street to the south from an entrance to the Masjid al Haram mosque, which houses the Kaaba. In order to start construction, the historic Ottoman Ajyad Fortress had to be first completely demolished. To accommodate worshipers visiting the Kaaba, the Abraj Al-Bait Towers will have a large prayer room capable of holding nearly ten thousand people. The tallest tower in the complex will also contain a seven-star hotel to help provide lodging for the over five million pilgrims who travel to Mecca annually to participate in hajj.
In addition, the Abraj Al-Bait Towers will have a four-story
shopping mall and a
parking garage capable of holding over a thousand vehicles. Residential towers will house permanent residents while two heliports and a
conference center are to accommodate
business travelers. In total, up to 100,000 people could be housed inside the towers. The project will use clock faces for each side of the hotel tower. The highest residential floor will be at 450 meters (1,480 feet), just below
the clocks. The clock faces will be 43 × 43 m (141 × 141 ft), the largest in the world. The roof of the clocks will be 530 metres (1,740 feet) above the ground, making them the world’s most elevated architectural clocks. A 71 meters (233 feet) tall spire will be added on top of the clock giving it a total height of 601 meters (1,972 feet), which will make it the second tallest building in the world when completed, surpassing Taipei 101 in Taiwan.
The tower will also include an Islamic Museum and a Lunar Observation Center which will also be used to sight the moonduring the holy months.
The complex is being built by the
Bin Laden Group, Saudi Arabia’s largest
construction company. The clock tower is being designed by the German company
Premiere Composite Technologies, the clock by the Swiss engineering firm
Strained. According to the Saudi Ministry of Religious Endowments, the project will cost $800 million.
Hormones that circulate in the blood could explain why older people have different
sleep patterns than younger people, a new study suggests.
The body’s circadian clock is determined by the expression of the circadian genes in the body’s cells, and the time for sleeping and waking are indicated by peaks in expression of these genes, the study said. Older people tend to have an earlier peak expression over a 24-hour period than younger people, which explains why they tend to
go to bed earlier and wake up earlier.
Scientists found they could manipulate the circadian clocks of skin cells from younger people to behave like those of older people, by growing those cells in the blood serum of older people, said study researcher Steven A. Brown, of the Institute for
Pharmacology and Toxicology at the University of Zurich in
Switzerland.This finding suggests some hormone or other circulating
molecule in the blood of older people has the ability to influence the cells’ circadian clocks, he said.
“A gene that had a peak expression at a particular time in cells from younger individuals might have this peak two hours earlier in the presence of serum from older individuals,” Brown told MyHealthNewsDaily.
The study was published today (April 11) in the
journal Proceedings of the National Academies of
Sciences.
Comparing circadian clocks:
Scientists grew skin cells from people in their 20s and people in their 60s in regular bovine serum cultures, and then in cultures made of blood serum from the 60-year-olds, according to the study.
They found that the cells from the 20-year-olds behaved like those of the 60-year-olds when they were grown in the blood serum.
“Human behavior shifts because activities normally done at one time of day” — like waking, eating or sleeping — “are now done earlier or late,” Brown said. “Cellular ‘behavior’ shifts in the same way: Something that the cell normally does at one time of day is done instead at another.”
Secrets of the skin cells:
Scientists have long known that skin cells have clocks that genetically
mirror their owners, he said.
“I can say whether you are a ‘lark’ or an ‘owl’ simply by looking at your skin cells,” Brown said. But “what is new here is that blood serum from older individuals makes cells from younger people ‘behave’ as if they were old.”
Other
factors also could account for the earlier sleep schedules of
elderly people, he said.
For example, elderly people may be exposed to less sunlight or may spend less time outdoors than younger people, which could have an impact their circadian clocks. Or, it’s possible that the blood-circulating molecule is somehow tied with these factors to influence sleep and wake cycles, he added.
