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Catherine of Aragon

Catherine of Aragon (also spelt as Katherine, historical Spanish: Catharina, now: Catalina; 16 December 1485 – 7 January 1536) was Queen of England as the first wife of King Henry VIII from their marriage on 11 June 1509 until its annulment on 23 May 1533. She was Princess of Wales while married to Henry's elder brother, Arthur, Prince of Wales, for a short period before his death.

Catherine was born at the Archbishop's Palace of Alcalá de Henares, and was the youngest child of Isabella I of Castile and Ferdinand II of Aragon. She was three years old when she was betrothed to Arthur, heir apparent to the English throne. They married in 1501, but Arthur died five months later. Catherine spent years in limbo, and during this time, she held the position of ambassador of the Aragonese crown to England in 1507, the first known female ambassador in European history. She married Henry shortly after his accession in 1509. For six months in 1513, she served as regent of England while Henry was in France. During that time the English defeated a Scottish invasion at the Battle of Flodden, an event in which Catherine played an important part with an emotional speech about courage and patriotism.

By 1526, Henry was infatuated with Anne Boleyn and dissatisfied that his marriage to Catherine had produced no surviving sons, leaving their daughter Mary as heir presumptive at a time when there was no established precedent for a woman on the throne. He sought to have their marriage annulled, setting in motion a chain of events that led to England's schism with the Catholic Church. When Pope Clement VII refused to annul the marriage, Henry defied him by assuming supremacy over religious matters in England. In 1533, their marriage was consequently declared invalid and Henry married Anne on the judgement of clergy in England, without reference to the pope. Catherine refused to accept Henry as supreme head of the Church in England and considered herself the king's rightful wife and queen, attracting much popular sympathy. Despite this, Henry acknowledged her only as dowager princess of Wales. After being banished from court by Henry, Catherine lived out the remainder of her life at Kimbolton Castle, dying there in January 1536 of cancer. The English people held Catherine in high esteem, and her death set off tremendous mourning. Her daughter Mary would become the first undisputed English queen regnant in 1553.

Catherine commissioned The Education of a Christian Woman by Juan Luis Vives, who dedicated the book, controversial at the time, to the Queen in 1523. Such was Catherine's impression on people that even her adversary Thomas Cromwell said of her, "If not for her sex, she could have defied all the heroes of History." She successfully appealed for the lives of the rebels involved in the Evil May Day, for the sake of their families, and also won widespread admiration by starting an extensive programme for the relief of the poor. Catherine was a patron of Renaissance humanism and a friend of the great scholars Erasmus of Rotterdam and Thomas More.

Early life
Catherine was born at the Archbishop's Palace of Alcalá de Henares near Madrid, in the early hours of 16 December 1485. She was the youngest surviving child of King Ferdinand II of Aragon and Queen Isabella I of Castile. Catherine was quite short in stature with long red hair, wide blue eyes, a round face, and a fair complexion. She was descended, on her maternal side, from the House of Lancaster, an English royal house; her great-grandmother Catherine of Lancaster, after whom she was named, and her great-great-grandmother Philippa of Lancaster were both daughters of John of Gaunt and granddaughters of Edward III of England. Consequently, she was third cousin of her father-in-law, Henry VII of England, and fourth cousin of her mother-in-law Elizabeth of York.

Catherine was educated by a tutor, Alessandro Geraldini, who was a clerk in Holy Orders. She studied arithmetic, canon and civil law, classical literature, genealogy and heraldry, history, philosophy, religion, and theology. She had a strong religious upbringing and developed her Roman Catholic faith that would play a major role in later life. She learned to speak, read and write in Castilian Spanish and Latin, and spoke French and Greek. Erasmus later said that Catherine "loved good literature which she had studied with success since childhood". She had been given lessons in domestic skills, such as cooking, embroidery, lace-making, needlepoint, sewing, spinning, and weaving and was also taught music, dancing, drawing, as well as being carefully educated in good manners and court etiquette.

At an early age, Catherine was considered a suitable wife for Arthur, Prince of Wales, heir apparent to the English throne, due to the English ancestry she inherited from her mother. Theoretically, by means of her mother, Catherine had a stronger legitimate claim to the English throne than King Henry VII himself through the first two wives of John of Gaunt, 1st Duke of Lancaster: Blanche of Lancaster and Constance of Castile. In contrast, Henry VII was the descendant of Gaunt's third marriage to Katherine Swynford, whose children were born out of wedlock and only legitimised after the death of Constance and the marriage of John to Katherine. The children of John and Katherine, while legitimised, were barred from inheriting the English throne, a stricture that was ignored in later generations. Because of Henry's descent through illegitimate children barred from succession to the English throne, the Tudor monarchy was not accepted by all European kingdoms. At the time, the House of Trastámara was the most prestigious in Europe, due to the rule of the Catholic Monarchs, so the alliance of Catherine and Arthur validated the House of Tudor in the eyes of European royalty and strengthened the Tudor claim to the English throne via Catherine of Aragon's ancestry. It would have given a male heir an indisputable claim to the throne. The two were married by proxy on 19 May 1499 and corresponded in Latin until Arthur turned fifteen, when it was decided that they were old enough to begin their conjugal life.

Catherine was accompanied to England by the following ambassadors: Diego Fernández de Córdoba y Mendoza, 3rd Count of Cabra; Alonso de Fonseca, Archbishop of Santiago de Compostela; and Antonio de Rojas Manrique, Bishop of Mallorca. She brought a group of her African attendants with her, including one identified as the trumpeter John Blanke. They are the first Africans recorded to have arrived in London at the time, and were considered luxury servants. They caused a great impression about the princess and the power of her family. Her Spanish retinue, including Francisco Felipe, was supervised by her duenna, Elvira Manuel.

At first it was thought Catherine's ship would arrive at Gravesend. A number of English gentlewomen were appointed to be ready to welcome her on arrival in October 1501. They were to escort Catherine in a flotilla of barges on the Thames to the Tower of London.

As wife and widow of Arthur

Then-15-year-old Catherine departed from A Coruña on 17 August 1501 and met Arthur on 4 November at Dogmersfield in Hampshire. Little is known about their first impressions of each other, but Arthur did write to his parents-in-law that he would be "a true and loving husband" and told his parents that he was immensely happy to "behold the face of his lovely bride". The couple had corresponded in Latin, but found that they could not understand each other's spoken conversation, because they had learned different Latin pronunciations. Ten days later, on 14 November 1501, they were married at Old St. Paul's Cathedral, both 15 years old. A dowry of 200,000 ducats had been agreed, and half was paid shortly after the marriage. It was noted that Catherine and her Spanish ladies in waiting were dressed in Spanish style at her arrival and at the wedding.

Once married, Arthur was sent to Ludlow Castle on the borders of Wales to preside over the Council of Wales and the Marches, as was his duty as Prince of Wales, and his bride accompanied him. A few months later, they both became ill, possibly with the sweating sickness, which was sweeping the area. Arthur died on 2 April 1502; 16-year-old Catherine recovered to find herself a widow.

At this point, Henry VII faced the challenge of avoiding the obligation to return her 200,000-ducat dowry, half of which he had not yet received, to her father, as required by her marriage contract should she return home. Following the death of Queen Elizabeth in February 1503, King Henry VII initially considered marrying Catherine himself, but the opposition of her father and potential questions over the legitimacy of the couple's issue ended the idea. To settle the matter, it was agreed that Catherine would marry Henry VII's second son, Henry, Duke of York, who was five years younger than she was. The death of Catherine's mother, however, meant that her "value" in the marriage market decreased. Castile was a much larger kingdom than Aragon, and it was inherited by Catherine's elder sister, Joanna. Ostensibly, the marriage was delayed until Henry was old enough, but Ferdinand II procrastinated so much over payment of the remainder of Catherine's dowry that it became doubtful that the marriage would take place. She lived as a virtual prisoner at Durham House in London. Some of the letters she wrote to her father complaining of her treatment have survived. In one of these letters she tells him that "I choose what I believe, and say nothing. For I am not as simple as I may seem." She had little money and struggled to cope, as she had to support her ladies-in-waiting as well as herself. In 1507 she served as the Spanish ambassador to England, the first female ambassador in European history. While Henry VII and his counsellors expected her to be easily manipulated, Catherine went on to prove them wrong.

Marriage to Arthur's brother depended on the Pope granting a dispensation because canon law forbade a man to marry his brother's widow (Lev. 18:16). Catherine testified that her marriage to Arthur was never consummated as, also according to canon law, a marriage was dissoluble unless consummated.

Wedding
Catherine's second wedding took place on 11 June 1509, seven years after Prince Arthur's death. She married Henry VIII, who had only just acceded to the throne, in a private ceremony in the church of the Observant Friars outside Greenwich Palace. She was 23 years of age.

Coronation
On Saturday 23 June 1509, the traditional eve-of-coronation procession to Westminster Abbey was greeted by a large and enthusiastic crowd. As was the custom, the couple spent the night before their coronation at the Tower of London. On Midsummer's Day, Sunday, 24 June 1509, Henry VIII and Catherine were anointed and crowned together by the Archbishop of Canterbury at a lavish ceremony at Westminster Abbey. The coronation was followed by a banquet in Westminster Hall. Many new Knights of the Bath were created in honour of the coronation. In that month that followed, many social occasions presented the new Queen to the English public. She made a fine impression and was well received by the people of England.

Influence

On 11 June 1513, Henry appointed Catherine Regent in England with the titles "Governor of the Realm and Captain General", while he went to France on a military campaign. When Louis d'Orléans, Duke of Longueville, was captured at Thérouanne, Henry sent him to stay in Catherine's household. She wrote to Wolsey that she and her council would prefer the Duke to stay in the Tower of London as the Scots were "so busy as they now be" and she added her prayers for "God to sende us as good lukke against the Scotts, as the King hath ther." The war with Scotland occupied her subjects, and she was "horrible busy with making standards, banners, and badges" at Richmond Palace. Catherine wrote to towns, including Gloucester, asking them to send muster lists of men able to serve as soldiers. The Scots invaded and on 3 September 1513, she ordered Thomas Lovell to raise an army in the midland counties.

Catherine was issued with banners at Richmond on 8 September, and rode north in full armour to address the troops, despite being heavily pregnant at the time. Her fine speech was reported to the historian Peter Martyr d'Anghiera in Valladolid within a fortnight. Although an Italian newsletter said she was 100 mi north of London when news of the victory at Battle of Flodden Field reached her, she was near Buckingham. From Woburn Abbey, she sent a letter to Henry along with a piece of the bloodied coat of King James IV of Scotland, who died in the battle, for Henry to use as a banner at the siege of Tournai.

Catherine's religious dedication increased as she became older, as did her interest in academics. She continued to broaden her knowledge and provide training for her daughter, Mary. Education among women became fashionable, partly because of Catherine's influence, and she donated large sums of money to several colleges. Henry, however, still considered a male heir essential. The Tudor dynasty was new, and its legitimacy might still be tested. A long civil war (1135–1154) had been fought the last time a woman (Empress Matilda) had inherited the throne. The disasters of civil war were still fresh in living memory from the Wars of the Roses.

In 1520, Catherine's nephew, the Holy Roman Emperor Charles V, paid a state visit to England, and she urged Henry to enter an alliance with Charles rather than with France. Immediately after his departure, she accompanied Henry to France on the celebrated visit to Francis I, the Field of the Cloth of Gold. Within two years, war was declared against France and the Emperor was once again welcome in England, where plans were afoot to betroth him to Catherine's daughter Mary.

The King's great matter

In 1525, Henry VIII became enamoured of Anne Boleyn, a lady-in-waiting to Queen Catherine; Anne was between ten and seventeen years younger than Henry, being born between 1501 and 1507. Henry began pursuing her; Catherine was no longer able to bear children by this time. Henry began to believe that his marriage was cursed and sought confirmation from the Bible, which he interpreted to say that if a man marries his brother's wife, the couple will be childless. Even if her marriage to Arthur had not been consummated (and Catherine would insist to her dying day that she had come to Henry's bed a virgin), Henry's interpretation of that biblical passage meant that their marriage had been wrong in the eyes of God. Whether the pope at the time of Henry and Catherine's marriage had the right to overrule Henry's claimed scriptural impediment would become a hot topic in Henry's campaign to wrest an annulment from the present Pope. It is possible that the idea of annulment had been suggested to Henry much earlier than this, and is highly probable that it was motivated by his desire for a son. Before Henry's father ascended the throne, England was beset by civil warfare over rival claims to the English crown, and Henry may have wanted to avoid a similar uncertainty over the succession.

It soon became the one absorbing object of Henry's desires to secure an annulment. Catherine was defiant when it was suggested that she quietly retire to a nunnery, saying: "God never called me to a nunnery. I am the King's true and legitimate wife." He set his hopes upon an appeal to the Holy See, acting independently of Cardinal Thomas Wolsey, whom he told nothing of his plans. William Knight, the King's secretary, was sent to Pope Clement VII to sue for an annulment, on the grounds that the dispensing bull of Pope Julius II was obtained by false pretenses.

As the pope was, at that time, the prisoner of Catherine's nephew Emperor Charles V following the Sack of Rome in May 1527, Knight had difficulty in obtaining access to him. In the end, Henry's envoy had to return without accomplishing much. Henry now had no choice but to put this great matter into the hands of Wolsey, who did all he could to secure a decision in Henry's favour.

Both the Pope and Martin Luther raised the possibility that Henry have two wives, not to re-introduce polygamy generally, but "to preserve the royal dignity of Catherine and Mary".

Wolsey went so far as to convene an ecclesiastical court in England with a representative of the pope presiding, and Henry and Catherine herself in attendance. The pope had no intention of allowing a decision to be reached in England, and his legate was recalled. (How far the pope was influenced by Charles V is difficult to say, but it is clear Henry saw that the pope was unlikely to annul his marriage to the emperor's aunt.) The Pope forbade Henry to marry again before a decision was given in Rome. Wolsey had failed and was dismissed from public office in 1529. Wolsey then began a secret plot to have Anne Boleyn forced into exile and began communicating with the pope to that end. When this was discovered, Henry ordered Wolsey's arrest and, had he not been terminally ill and died in 1530, he might have been executed for treason.

A year later, Catherine was banished from court, and her old rooms were given to Anne Boleyn. Catherine wrote in a letter to Charles V in 1531:

"My tribulations are so great, my life so disturbed by the plans daily invented to further the King's wicked intention, the surprises which the King gives me, with certain persons of his council, are so mortal, and my treatment is what God knows, that it is enough to shorten ten lives, much more mine."

When Archbishop of Canterbury William Warham died, the Boleyn family's chaplain, Thomas Cranmer, was appointed to the vacant position.

When Henry decided to annul his marriage to Catherine, John Fisher became her most trusted counsellor and one of her chief supporters. He appeared in the legates' court on her behalf, where he shocked people with the directness of his language, and by declaring that, like John the Baptist, he was ready to die on behalf of the indissolubility of marriage. Henry was so enraged by this that he wrote a long Latin address to the legates in answer to Fisher's speech. Fisher's copy of this still exists, with his manuscript annotations in the margin which show how little he feared Henry's anger. The removal of the cause to Rome ended Fisher's role in the matter, but Henry never forgave him. Other people who supported Catherine's case included Thomas More; Henry's own sister Mary Tudor, Queen of France; María de Salinas; Holy Roman Emperor Charles V; Pope Paul III; and Protestant Reformers Martin Luther and William Tyndale.

Banishment and death
Upon returning to Dover from a meeting with King Francis I of France in Calais, Henry married Anne Boleyn in a secret ceremony. Some sources speculate that Anne was already pregnant at the time (and Henry did not want to risk a son being born illegitimate) but others testify that Anne (who had seen her sister Mary Boleyn taken up as the king's mistress and summarily cast aside) refused to sleep with Henry until they were married. Henry defended the lawfulness of their union by pointing out that Catherine had previously been married. If she and Arthur had consummated their marriage, Henry by canon law had the right to remarry. On 23 May 1533, Cranmer, sitting in judgement at a special court convened at Dunstable Priory to rule on the validity of Henry's marriage to Catherine, declared the marriage unlawful, even though Catherine had testified that she and Arthur had never had physical relations. Five days later, on 28 May 1533, Cranmer ruled that Henry and Anne's marriage was valid.

Until the end of her life, Catherine would refer to herself as Henry's only lawful wedded wife and England's only rightful queen, and her servants continued to address her as such. Henry refused her the right to any title but "Dowager Princess of Wales" in recognition of her position as his brother's widow.

Catherine went to live at The More Castle, Hertfordshire, late in 1531. After that, she was successively moved to the Royal Palace of Hatfield, Hertfordshire (May to September 1532), Elsyng Palace, Enfield (September 1532 to February 1533), Ampthill Castle, Bedfordshire (February to July 1533) and Buckden Towers, Cambridgeshire (July 1533 to May 1534). She was then finally transferred to Kimbolton Castle, Cambridgeshire where she confined herself to one room, which she left only to attend Mass, dressed only in the hair shirt of the Order of St. Francis, and fasted continuously. While she was permitted to receive occasional visitors, she was forbidden to see her daughter Mary. They were also forbidden to communicate in writing, but sympathisers discreetly conveyed letters between the two. Henry offered both mother and daughter better quarters and permission to see each other if they would acknowledge Anne Boleyn as the new queen; both refused.

In late December 1535, sensing her death was near, Catherine made her will, and wrote to her nephew, the Emperor Charles V, asking him to protect her daughter. It has been claimed that she then penned one final letter to Henry:

The authenticity of the letter itself has been questioned, but not Catherine's attitude in its wording, which has been reported with variations in different sources.

Catherine died at Kimbolton Castle on 7 January 1536. The following day, news of her death reached the king. At the time there were rumours that she was poisoned,  possibly by Gregory di Casale. According to the chronicler Edward Hall, Anne Boleyn wore yellow for the mourning, which has been interpreted in various ways; Polydore Vergil interpreted this to mean that Anne did not mourn. Chapuys reported that it was King Henry who decked himself in yellow, celebrating the news and making a great show of his and Anne's daughter, Elizabeth, to his courtiers. This was seen as distasteful and vulgar by many. Another theory is that the dressing in yellow was out of respect for Catherine as yellow was said to be the Spanish colour of mourning. Certainly, later in the day it is reported that Henry and Anne both individually and privately wept for her death. On the day of Catherine's funeral, Anne Boleyn miscarried a male child. Rumours then circulated that Catherine had been poisoned by Anne or Henry, or both. The rumours were born after the apparent discovery during her embalming that there was a black growth on her heart that might have been caused by poisoning. Modern medical experts are in agreement that her heart's discolouration was due not to poisoning, but to cancer, something which was not understood at the time.

Catherine was buried in Peterborough Cathedral with the ceremony due to her position as a Dowager Princess of Wales, and not a queen. Henry did not attend the funeral and forbade Mary to attend.

Faith
Catherine was a member of the Third Order of Saint Francis and she was punctilious in her religious obligations in the Order, integrating without demur her necessary duties as queen with her personal piety. After the annulment, she was quoted "I would rather be a poor beggar's wife and be sure of heaven, than queen of all the world and stand in doubt thereof by reason of my own consent."

The outward celebration of saints and holy relics formed no major part of her personal devotions, which she rather expressed in the Mass, prayer, confession and penance. Privately, however, she was aware of what she identified as the shortcomings of the papacy and church officialdom. Her doubts about church improprieties certainly did not extend so far as to support the allegations of corruption made public by Martin Luther in Wittenberg in 1517, which were soon to have such far-reaching consequences in initiating the Protestant Reformation.

In 1523 Alfonso de Villa Sancta, a learned friar of the Observant (reform) branch of the Friars Minor and friend of the king's old advisor Erasmus, dedicated to the queen his book De Liberio Arbitrio adversus Melanchthonem. The book denounced Philip Melanchthon, a supporter of Luther. Acting as her confessor, he was able to nominate her for the title of "Defender of the Faith" for denying Luther's arguments.

Appearance
In her youth, Catherine was described as "the most beautiful creature in the world" and that there was "nothing lacking in her that the most beautiful girl should have". Thomas More and Lord Herbert would reflect later in her lifetime that in regard to her appearance "there were few women who could compete with the Queen [Catherine] in her prime."

Legacy, memory and historiography

The controversial book The Education of a Christian Woman by Juan Luis Vives, which claimed women have the right to an education, was dedicated to and commissioned by her. Such was Catherine's impression on people, that even her enemy, Thomas Cromwell, said of her "If not for her sex, she could have defied all the heroes of History." She successfully appealed for the lives of the rebels involved in the Evil May Day for the sake of their families. Furthermore, Catherine won widespread admiration by starting an extensive programme for the relief of the poor. She was also a patron of Renaissance humanism, and a friend of the great scholars Erasmus of Rotterdam and Saint Thomas More. Some saw her as a martyr.

In the reign of her daughter Mary I of England, her marriage to Henry VIII was declared "good and valid". Her daughter Queen Mary also had several portraits commissioned of Catherine, and it would not by any means be the last time she was painted. After her death, numerous portraits were painted of her, particularly of her speech at the Legatine Trial, a moment accurately rendered in Shakespeare's play about Henry VIII.

Her tomb in Peterborough Cathedral can be seen and there is hardly ever a time when it is not decorated with flowers or pomegranates, her heraldic symbol. It bears the title Katharine Queen of England.

In the 20th century, George V's wife, Mary of Teck, had her grave upgraded and there are now banners there denoting Catherine as a Queen of England. Every year at Peterborough Cathedral there is a service in her memory. There are processions, prayers and various events in the Cathedral including processions to Catherine's grave in which candles, pomegranates, flowers and other offerings are placed on her grave. On the service commemorating the 470th anniversary of her death, the Spanish Ambassador to the United Kingdom attended. During the 2010 service a rendition of Catherine of Aragon's speech before the Legatine court was read by Jane Lapotaire. There is a statue of her in her birthplace of Alcalá de Henares, as a young woman holding a book and a rose.

Catherine has remained a popular biographical subject to the present day. The American historian Garrett Mattingly was the author of a popular biography Katherine of Aragon in 1942. In 1966, Catherine and her many supporters at court were the subjects of Catherine of Aragon and her Friends, a biography by John E. Paul. In 1967, Mary M. Luke wrote the first book of her Tudor trilogy, Catherine the Queen which portrayed her and the tumultuous era of English history through which she lived. In recent years, the historian Alison Weir covered her life extensively in her biography The Six Wives of Henry VIII, first published in 1991. Antonia Fraser did the same in her own 1992 biography of the same title; as did the British historian David Starkey in his 2003 book Six Wives: The Queens of Henry VIII. Giles Tremlett's biography, Catherine of Aragon: The Spanish Queen of Henry VIII, came out in 2010, and Julia Fox's dual biography, Sister Queens: The Noble, Tragic Lives of Katherine of Aragon and Juana, Queen of Castile, came out in 2011.

Places and statues

 * In Alcalá de Henares, the place of Catherine's birth, a statue of Catherine as a young woman holding a rose and a book can be seen in the Archbishop's Palace.
 * Peterborough is twinned with the Spanish city of Alcalá de Henares, located in the wider Community of Madrid. Children from schools in the two places have learned about each other as part of the twinning venture, and artists have even come over from Alcalá de Henares to paint Catherine's tombstone.
 * Many places in Ampthill are named after Catherine. Also in Ampthill there is a cross in Ampthill Great Park named "Queen Catherine's Cross" in her honour. It is on the site of the castle where she was sent during her divorce from the King.
 * Kimbolton School's science and mathematics block is called the QKB, or Queen Katherine Building.

Spelling of her name
Her baptismal name was "Catalina", but "Katherine" was soon the accepted form in England after her marriage to Arthur. Catherine herself signed her name "Katherine", "Katherina", "Katharine" and sometimes "Katharina". In a letter to her, Arthur, her husband, addressed her as "Princess Katerine". Her daughter Queen Mary I called her "Quene Kateryn", in her will. Rarely were names, particularly first names, written in an exact manner during the sixteenth century and it is evident from Catherine's own letters that she endorsed different variations. Loveknots built into his various palaces by her husband, Henry VIII, display the initials "H & K", as do other items belonging to Henry and Catherine, including gold goblets, a gold salt cellar, basins of gold, and candlesticks. Her tomb in Peterborough Cathedral is marked "Katharine Queen of England".

title: Catherine of Aragon


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Cathode ray

Cathode rays or electron beams (e-beam) are streams of electrons observed in discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the cathode (the electrode connected to the negative terminal of the voltage supply). They were first observed in 1859 by German physicist Julius Plücker and Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein Kathodenstrahlen, or cathode rays. In 1897, British physicist J. J. Thomson showed that cathode rays were composed of a previously unknown negatively charged particle, which was later named the electron. Cathode-ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to render an image on a screen.

Description

Cathode rays are so named because they are emitted by the negative electrode, or cathode, in a vacuum tube. To release electrons into the tube, they first must be detached from the atoms of the cathode. In the early experimental cold cathode vacuum tubes in which cathode rays were discovered, called Crookes tubes, this was done by using a high electrical potential of thousands of volts between the anode and the cathode to ionize the residual gas atoms in the tube. The positive ions were accelerated by the electric field toward the cathode, and when they collided with it they knocked electrons out of its surface; these were the cathode rays. Modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament which is heated by a separate electric current passing through it. The increased random heat motion of the filament knocks electrons out of the surface of the filament, into the evacuated space of the tube.

Since the electrons have a negative charge, they are repelled by the negative cathode and attracted to the positive anode. They travel in parallel lines through the empty tube. The voltage applied between the electrodes accelerates these low mass particles to high velocities. Cathode rays are invisible, but their presence was first detected in these Crookes tubes when they struck the glass wall of the tube, exciting the atoms of the glass coating and causing them to emit light, a glow called fluorescence. Researchers noticed that objects placed in the tube in front of the cathode could cast a shadow on the glowing wall, and realized that something must be traveling in straight lines from the cathode. After the electrons strike the back of the tube they make their way to the anode, then travel through the anode wire through the power supply and back through the cathode wire to the cathode, so cathode rays carry electric current through the tube.

The current in a beam of cathode rays through a vacuum tube can be controlled by passing it through a metal screen of wires (a grid) between cathode and anode, to which a small negative voltage is applied. The electric field of the wires deflects some of the electrons, preventing them from reaching the anode. The amount of current that gets through to the anode depends on the voltage on the grid. Thus, a small voltage on the grid can be made to control a much larger voltage on the anode. This is the principle used in vacuum tubes to amplify electrical signals. The triode vacuum tube developed between 1907 and 1914 was the first electronic device that could amplify, and is still used in some applications such as radio transmitters. High speed beams of cathode rays can also be steered and manipulated by electric fields created by additional metal plates in the tube to which voltage is applied, or magnetic fields created by coils of wire (electromagnets). These are used in cathode-ray tubes, found in televisions and computer monitors, and in electron microscopes.

History
After the 1654 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with passing high voltage electricity through rarefied air. In 1705, it was noted that electrostatic generator sparks travel a longer distance through low pressure air than through atmospheric pressure air.

Gas discharge tubes

In 1838, Michael Faraday applied a high voltage between two metal electrodes at either end of a glass tube that had been partially evacuated of air, and noticed a strange light arc with its beginning at the cathode (negative electrode) and its end at the anode (positive electrode). In 1857, German physicist and glassblower Heinrich Geissler sucked even more air out with an improved pump, to a pressure of around 10−3 atm and found that, instead of an arc, a glow filled the tube. The voltage applied between the two electrodes of the tubes, generated by an induction coil, was anywhere between a few kilovolts and 100 kV. These were called Geissler tubes, similar to today's neon signs.

The explanation of these effects was that the high voltage accelerated free electrons and electrically charged atoms (ions) naturally present in the air of the tube. At low pressure, there was enough space between the gas atoms that the electrons could accelerate to high enough speeds that when they struck an atom they knocked electrons off of it, creating more positive ions and free electrons, which went on to create more ions and electrons in a chain reaction, known as a glow discharge. The positive ions were attracted to the cathode and when they struck it knocked more electrons out of it, which were attracted toward the anode. Thus the ionized air was electrically conductive and an electric current flowed through the tube.

Geissler tubes had enough air in them that the electrons could only travel a tiny distance before colliding with an atom. The electrons in these tubes moved in a slow diffusion process, never gaining much speed, so these tubes didn't produce cathode rays. Instead, they produced a colorful glow discharge (as in a modern neon light), caused when the electrons struck gas atoms, exciting their orbital electrons to higher energy levels. The electrons released this energy as light. This process is called fluorescence.

Cathode rays
By the 1870s, British physicist William Crookes and others were able to evacuate tubes to a lower pressure, below 10−6 atm. These were called Crookes tubes. Faraday had been the first to notice a dark space just in front of the cathode, where there was no luminescence. This came to be called the "cathode dark space", "Faraday dark space" or "Crookes dark space". Crookes found that as he pumped more air out of the tubes, the Faraday dark space spread down the tube from the cathode toward the anode, until the tube was totally dark. But at the anode (positive) end of the tube, the glass of the tube itself began to glow.

What was happening was that as more air was pumped from the tube, the electrons knocked out of the cathode when positive ions struck it could travel farther, on average, before they struck a gas atom. By the time the tube was dark, most of the electrons could travel in straight lines from the cathode to the anode end of the tube without a collision. With no obstructions, these low mass particles were accelerated to high velocities by the voltage between the electrodes. These were the cathode rays.

When they reached the anode end of the tube, they were traveling so fast that, although they were attracted to it, they often flew past the anode and struck the back wall of the tube. When they struck atoms in the glass wall, they excited their orbital electrons to higher energy levels. When the electrons returned to their original energy level, they released the energy as light, causing the glass to fluoresce, usually a greenish or bluish color. Later researchers painted the inside back wall with fluorescent chemicals such as zinc sulfide, to make the glow more visible.

Cathode rays themselves are invisible, but this accidental fluorescence allowed researchers to notice that objects in the tube in front of the cathode, such as the anode, cast sharp-edged shadows on the glowing back wall. In 1869, German physicist Johann Hittorf was first to realize that something must be traveling in straight lines from the cathode to cast the shadows. Eugen Goldstein named them cathode rays (German Kathodenstrahlen).

Discovery of the electron
At this time, atoms were the smallest particles known, and were believed to be indivisible. What carried electric currents was a mystery. During the last quarter of the 19th century, many historic experiments were done with Crookes tubes to determine what cathode rays were. There were two theories. Crookes and Arthur Schuster believed they were particles of "radiant matter," that is, electrically charged atoms. German scientists Eilhard Wiedemann, Heinrich Hertz and Goldstein believed they were "aether waves", some new form of electromagnetic radiation, and were separate from what carried the electric current through the tube.

The debate was resolved in 1897 when J. J. Thomson measured the mass of cathode rays, showing they were made of particles, but were around 1800 times lighter than the lightest atom, hydrogen. Therefore, they were not atoms, but a new particle, the first subatomic particle to be discovered, which he originally called "corpuscle" but was later named electron, after particles postulated by George Johnstone Stoney in 1874. He also showed they were identical with particles given off by photoelectric and radioactive materials. It was quickly recognized that they are the particles that carry electric currents in metal wires, and carry the negative electric charge of the atom.

Thomson was given the 1906 Nobel Prize in Physics for this work. Philipp Lenard also contributed a great deal to cathode-ray theory, winning the Nobel Prize in 1905 for his research on cathode rays and their properties.

Vacuum tubes
The gas ionization (or cold cathode) method of producing cathode rays used in Crookes tubes was unreliable, because it depended on the pressure of the residual air in the tube. Over time, the air was absorbed by the walls of the tube, and it stopped working.

A more reliable and controllable method of producing cathode rays was investigated by Hittorf and Goldstein, and rediscovered by Thomas Edison in 1880. A cathode made of a wire filament heated red hot by a separate current passing through it would release electrons into the tube by a process called thermionic emission. The first true electronic vacuum tubes, invented in 1904 by John Ambrose Fleming, used this hot cathode technique, and they superseded Crookes tubes. These tubes didn't need gas in them to work, so they were evacuated to a lower pressure, around 10−9 atm (10−4 Pa). The ionization method of creating cathode rays used in Crookes tubes is today only used in a few specialized gas discharge tubes such as krytrons.

In 1906, Lee De Forest found that a small voltage on a grid of metal wires between the cathode and anode could control a current in a beam of cathode rays passing through a vacuum tube. His invention, called the triode, was the first device that could amplify electric signals, and revolutionized electrical technology, creating the new field of electronics. Vacuum tubes made radio and television broadcasting possible, as well as radar, talking movies, audio recording, and long-distance telephone service, and were the foundation of consumer electronic devices until the 1960s, when the transistor brought the era of vacuum tubes to a close.

Cathode rays are now usually called electron beams. The technology of manipulating electron beams pioneered in these early tubes was applied practically in the design of vacuum tubes, particularly in the invention of the cathode-ray tube (CRT) by Ferdinand Braun in 1897, which was used in television sets and oscilloscopes. Today, electron beams are employed in sophisticated devices such as electron microscopes, electron beam lithography and particle accelerators.

Properties
Like a wave, cathode rays travel in straight lines, and produce a shadow when obstructed by objects. Ernest Rutherford demonstrated that rays could pass through thin metal foils, behavior expected of a particle. These conflicting properties caused disruptions when trying to classify it as a wave or particle. Crookes insisted it was a particle, while Hertz maintained it was a wave. The debate was resolved when an electric field was used to deflect the rays by J. J. Thomson. This was evidence that the beams were composed of particles because scientists knew it was impossible to deflect electromagnetic waves with an electric field. These can also create mechanical effects, fluorescence, etc.

Louis de Broglie later (1924) suggested in his doctoral dissertation that electrons are like photons and can act as waves. The wave-like behaviour of cathode rays was later directly demonstrated using reflection from a nickel surface by Davisson and Germer, and transmission through celluloid thin films and later metal films by George Paget Thomson and Alexander Reid in 1927. (Alexander Reid, who was Thomson's graduate student, performed the first experiments but he died soon after in a motorcycle accident and is rarely mentioned.)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Cathode ray


text:
Cathode

A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic CCD for Cathode Current Departs. A conventional current describes the direction in which positive charges move. Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode from the external circuit. For example, the end of a household battery marked with a + (plus) is the cathode.

The electrode through which conventional current flows the other way, into the device, is termed an anode.

Charge flow
Conventional current flows from cathode to anode outside the cell or device (with electrons moving in the opposite direction), regardless of the cell or device type and operating mode.

Cathode polarity with respect to the anode can be positive or negative depending on how the device is being operated. Inside a device or a cell, positively charged cations always move towards the cathode and negatively charged anions move towards the anode, although cathode polarity depends on the device type, and can even vary according to the operating mode. Whether the cathode is negatively polarized (such as recharging a battery) or positively polarized (such as a battery in use), the cathode will draw electrons into it from outside, as well as attract positively charged cations from inside.

A battery or galvanic cell in use has a cathode that is the positive terminal since that is where conventional current flows out of the device. This outward current is carried internally by positive ions moving from the electrolyte to the positive cathode (chemical energy is responsible for this "uphill" motion). It is continued externally by electrons moving into the battery which constitutes positive current flowing outwards. For example, the Daniell galvanic cell's copper electrode is the positive terminal and the cathode.

A battery that is recharging or an electrolytic cell performing electrolysis has its cathode as the negative terminal, from which current exits the device and returns to the external generator as charge enters the battery/ cell. For example, reversing the current direction in a Daniell galvanic cell converts it into an electrolytic cell where the copper electrode is the positive terminal and also the anode.

In a diode, the cathode is the negative terminal at the pointed end of the arrow symbol, where current flows out of the device. Note: electrode naming for diodes is always based on the direction of the forward current (that of the arrow, in which the current flows "most easily"), even for types such as Zener diodes or solar cells where the current of interest is the reverse current. In vacuum tubes (including cathode-ray tubes) it is the negative terminal where electrons enter the device from the external circuit and proceed into the tube's near-vacuum, constituting a positive current flowing out of the device.

Etymology
The word was coined in 1834 from the Greek κάθοδος (kathodos), 'descent' or 'way down', by William Whewell, who had been consulted by Michael Faraday over some new names needed to complete a paper on the recently discovered process of electrolysis. In that paper Faraday explained that when an electrolytic cell is oriented so that electric current traverses the "decomposing body" (electrolyte) in a direction "from East to West, or, which will strengthen this help to the memory, that in which the sun appears to move", the cathode is where the current leaves the electrolyte, on the West side: "kata downwards, `odos a way; the way which the sun sets".

The use of 'West' to mean the 'out' direction (actually 'out' → 'West' → 'sunset' → 'down', i.e. 'out of view') may appear unnecessarily contrived. Previously, as related in the first reference cited above, Faraday had used the more straightforward term "exode" (the doorway where the current exits). His motivation for changing it to something meaning 'the West electrode' (other candidates had been "westode", "occiode" and "dysiode") was to make it immune to a possible later change in the direction convention for current, whose exact nature was not known at the time. The reference he used to this effect was the Earth's magnetic field direction, which at that time was believed to be invariant. He fundamentally defined his arbitrary orientation for the cell as being that in which the internal current would run parallel to and in the same direction as a hypothetical magnetizing current loop around the local line of latitude which would induce a magnetic dipole field oriented like the Earth's. This made the internal current East to West as previously mentioned, but in the event of a later convention change it would have become West to East, so that the West electrode would not have been the 'way out' any more. Therefore, "exode" would have become inappropriate, whereas "cathode" meaning 'West electrode' would have remained correct with respect to the unchanged direction of the actual phenomenon underlying the current, then unknown but, he thought, unambiguously defined by the magnetic reference. In retrospect the name change was unfortunate, not only because the Greek roots alone do not reveal the cathode's function any more, but more importantly because, as we now know, the Earth's magnetic field direction on which the "cathode" term is based is subject to reversals whereas the current direction convention on which the "exode" term was based has no reason to change in the future.

Since the later discovery of the electron, an easier to remember, and more durably technically correct (although historically false), etymology has been suggested: cathode, from the Greek kathodos, 'way down', 'the way (down) into the cell (or other device) for electrons'.

In chemistry
In chemistry, a cathode is the electrode of an electrochemical cell at which reduction occurs. The cathode can be negative like when the cell is electrolytic (where electrical energy provided to the cell is being used for decomposing chemical compounds); or positive as when the cell is galvanic (where chemical reactions are used for generating electrical energy). The cathode supplies electrons to the positively charged cations which flow to it from the electrolyte (even if the cell is galvanic, i.e., when the cathode is positive and therefore would be expected to repel the positively charged cations; this is due to electrode potential relative to the electrolyte solution being different for the anode and cathode metal/electrolyte systems in a galvanic cell).

The cathodic current, in electrochemistry, is the flow of electrons from the cathode interface to a species in solution. The anodic current is the flow of electrons into the anode from a species in solution.

Electrolytic cell
In an electrolytic cell, the cathode is where the negative polarity is applied to drive the cell. Common results of reduction at the cathode are hydrogen gas or pure metal from metal ions. When discussing the relative reducing power of two redox agents, the couple for generating the more reducing species is said to be more "cathodic" with respect to the more easily reduced reagent.

Galvanic cell
In a galvanic cell, the cathode is where the positive pole is connected to allow the circuit to be completed: as the anode of the galvanic cell gives off electrons, they return from the circuit into the cell through the cathode.

Electroplating metal cathode (electrolysis)
When metal ions are reduced from ionic solution, they form a pure metal surface on the cathode. Items to be plated with pure metal are attached to and become part of the cathode in the electrolytic solution.

Vacuum tubes

In a vacuum tube or electronic vacuum system, the cathode is a metal surface which emits free electrons into the evacuated space. Since the electrons are attracted to the positive nuclei of the metal atoms, they normally stay inside the metal and require energy to leave it; this is called the work function of the metal. Cathodes are induced to emit electrons by several mechanisms:
 * Thermionic emission: The cathode can be heated. The increased thermal motion of the metal atoms "knocks" electrons out of the surface, an effect called thermionic emission. This technique is used in most vacuum tubes.
 * Field electron emission: A strong electric field can be applied to the surface by placing an electrode with a high positive voltage near the cathode.  The positively charged electrode attracts the electrons, causing some electrons to leave the cathode's surface.  This process is used in cold cathodes in some electron microscopes,  and in microelectronics fabrication,
 * Secondary emission: An electron, atom or molecule colliding with the surface of the cathode with enough energy can knock electrons out of the surface. These electrons are called secondary electrons. This mechanism is used in gas-discharge lamps such as neon lamps.
 * Photoelectric emission: Electrons can also be emitted from the electrodes of certain metals when light of frequency greater than the threshold frequency falls on it. This effect is called photoelectric emission, and the electrons produced are called photoelectrons. This effect is used in phototubes and image intensifier tubes.

Cathodes can be divided into two types:

Hot cathode

A hot cathode is a cathode that is heated by a filament to produce electrons by thermionic emission. The filament is a thin wire of a refractory metal like tungsten heated red-hot by an electric current passing through it. Before the advent of transistors in the 1960s, virtually all electronic equipment used hot-cathode vacuum tubes. Today hot cathodes are used in vacuum tubes in radio transmitters and microwave ovens, to produce the electron beams in older cathode-ray tube (CRT) type televisions and computer monitors, in x-ray generators, electron microscopes, and fluorescent tubes.

There are two types of hot cathodes:
 * Directly heated cathode: In this type, the filament itself is the cathode and emits the electrons directly. Directly heated cathodes were used in the first vacuum tubes, but today they are only used in fluorescent tubes, some large transmitting vacuum tubes, and all X-ray tubes.
 * Indirectly heated cathode: In this type, the filament is not the cathode but rather heats the cathode which then emits electrons. Indirectly heated cathodes are used in most devices today. For example, in most vacuum tubes the cathode is a nickel tube with the filament inside it, and the heat from the filament causes the outside surface of the tube to emit electrons.  The filament of an indirectly heated cathode is usually called the heater.   The main reason for using an indirectly heated cathode is to isolate the rest of the vacuum tube from the electric potential across the filament. Many vacuum tubes use alternating current to heat the filament. In a tube in which the filament itself was the cathode, the alternating electric field from the filament surface would affect the movement of the electrons and introduce hum into the tube output. It also allows the filaments in all the tubes in an electronic device to be tied together and supplied from the same current source, even though the cathodes they heat may be at different potentials.

In order to improve electron emission, cathodes are treated with chemicals, usually compounds of metals with a low work function. Treated cathodes require less surface area, lower temperatures and less power to supply the same cathode current. The untreated tungsten filaments used in early tubes (called "bright emitters") had to be heated to 1400 °C, white-hot, to produce sufficient thermionic emission for use, while modern coated cathodes produce far more electrons at a given temperature so they only have to be heated to 425 –  There are two main types of treated cathodes:

 * Coated cathode – In these the cathode is covered with a coating of alkali metal oxides, often barium and strontium oxide. These are used in low-power tubes.
 * Thoriated tungsten – In high-power tubes, ion bombardment can destroy the coating on a coated cathode.  In these tubes a directly heated cathode consisting of a filament made of tungsten incorporating a small amount of thorium is used. The layer of thorium on the surface which reduces the work function of the cathode is continually replenished as it is lost by diffusion of thorium from the interior of the metal.

Cold cathode
This is a cathode that is not heated by a filament. They may emit electrons by field electron emission, and in gas-filled tubes by secondary emission. Some examples are electrodes in neon lights, cold-cathode fluorescent lamps (CCFLs) used as backlights in laptops, thyratron tubes, and Crookes tubes. They do not necessarily operate at room temperature; in some devices the cathode is heated by the electron current flowing through it to a temperature at which thermionic emission occurs. For example, in some fluorescent tubes a momentary high voltage is applied to the electrodes to start the current through the tube; after starting the electrodes are heated enough by the current to keep emitting electrons to sustain the discharge.

Cold cathodes may also emit electrons by photoelectric emission. These are often called photocathodes and are used in phototubes used in scientific instruments and image intensifier tubes used in night vision goggles.

Diodes
In a semiconductor diode, the cathode is the N–doped layer of the PN junction with a high density of free electrons due to doping, and an equal density of fixed positive charges, which are the dopants that have been thermally ionized. In the anode, the converse applies: It features a high density of free "holes" and consequently fixed negative dopants which have captured an electron (hence the origin of the holes).

When P and N-doped layers are created adjacent to each other, diffusion ensures that electrons flow from high to low density areas: That is, from the N to the P side. They leave behind the fixed positively charged dopants near the junction. Similarly, holes diffuse from P to N leaving behind fixed negative ionised dopants near the junction. These layers of fixed positive and negative charges are collectively known as the depletion layer because they are depleted of free electrons and holes. The depletion layer at the junction is at the origin of the diode's rectifying properties. This is due to the resulting internal field and corresponding potential barrier which inhibit current flow in reverse applied bias which increases the internal depletion layer field. Conversely, they allow it in forwards applied bias where the applied bias reduces the built in potential barrier.

Electrons which diffuse from the cathode into the P-doped layer, or anode, become what are termed "minority carriers" and tend to recombine there with the majority carriers, which are holes, on a timescale characteristic of the material which is the p-type minority carrier lifetime. Similarly, holes diffusing into the N-doped layer become minority carriers and tend to recombine with electrons. In equilibrium, with no applied bias, thermally assisted diffusion of electrons and holes in opposite directions across the depletion layer ensure a zero net current with electrons flowing from cathode to anode and recombining, and holes flowing from anode to cathode across the junction or depletion layer and recombining.

Like a typical diode, there is a fixed anode and cathode in a Zener diode, but it will conduct current in the reverse direction (electrons flow from anode to cathode) if its breakdown voltage or "Zener voltage" is exceeded.

title: Cathode


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Chrominance

Chrominance (chroma or C for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying luma signal (or Y' for short). Chrominance is usually represented as two color-difference components: U = B′ − Y′ (blue − luma) and V = R′ − Y′ (red − luma). Each of these different components may have scale factors and offsets applied to it, as specified by the applicable video standard.

In composite video signals, the U and V signals modulate a color subcarrier signal, and the result is referred to as the chrominance signal; the phase and amplitude of this modulated chrominance signal correspond approximately to the hue and saturation of the color. In digital-video and still-image color spaces such as Y′CbCr, the luma and chrominance components are digital sample values.

Separating RGB color signals into luma and chrominance allows the bandwidth of each to be determined separately. Typically, the chrominance bandwidth is reduced in analog composite video by reducing the bandwidth of a modulated color subcarrier, and in digital systems by chroma subsampling.

History
The idea of transmitting a color television signal with distinct luma and chrominance components originated with Georges Valensi, who patented the idea in 1938. Valensi's patent application described:

The use of two channels, one transmitting the predominating color (signal T), and the other the mean brilliance (signal t) output from a single television transmitter to be received not only by color television receivers provided with the necessary more expensive equipment, but also by the ordinary type of television receiver which is more numerous and less expensive and which reproduces the pictures in black and white only.

Previous schemes for color television systems, which were incompatible with existing monochrome receivers, transmitted RGB signals in various ways.

Television standards
In analog television, chrominance is encoded into a video signal using a subcarrier frequency. Depending on the video standard, the chrominance subcarrier may be either quadrature-amplitude-modulated (NTSC and PAL) or frequency-modulated (SECAM).

In the PAL system, the color subcarrier is 4.43 MHz above the video carrier, while in the NTSC system it is 3.58 MHz above the video carrier. The NTSC and PAL standards are the most commonly used, although there are other video standards that employ different subcarrier frequencies. For example, PAL-M (Brazil) uses a 3.58 MHz subcarrier, and SECAM uses two different frequencies, 4.250 MHz and 4.40625 MHz above the video carrier.

The presence of chrominance in a video signal is indicated by a color burst signal transmitted on the back porch, just after horizontal synchronization and before each line of video starts. If the color burst signal were visible on a television screen, it would appear as a vertical strip of a very dark olive color. In NTSC and PAL, hue is represented by a phase shift of the chrominance signal relative to the color burst, while saturation is determined by the amplitude of the subcarrier. In SECAM (R′ − Y′) and (B′ − Y′) signals are transmitted alternately and phase does not matter.

Chrominance is represented by the U-V color plane in PAL and SECAM video signals, and by the I-Q color plane in NTSC.

Digital systems
Digital video and digital still photography systems sometimes use a luma/chroma decomposition for improved compression. For example, when an ordinary RGB digital image is compressed via the JPEG standard, the RGB color space is first converted (by a rotation matrix) to a YCbCr color space, because the three components in that space have less correlation redundancy and because the chrominance components can then be subsampled by a factor of 2 or 4 to further compress the image. On decompression, the Y′CbCr space is rotated back to RGB.

title: Chrominance


text:
Chirality (disambiguation)

Chirality (handedness) is a property of asymmetry.

Chirality may also refer to:

 * Chirality (chemistry), a property of molecules having a non-superimposable mirror image
 * Chirality (electromagnetism), an electromagnetic propagation in chiral media
 * Chirality (mathematics), the property of a figure not being identical to its mirror image
 * Chirality (physics), when a phenomenon is not identical to its mirror image
 * Chirality (journal), an academic journal dealing with chiral chemistry
 * Chirality (manga), a 4-volume yuri manga series written and illustrated by author Satoshi Urushihara
 * Chirality (album), a 2014 solo piano album by American pianist John Burke

title: Chirality (disambiguation)


text:
Campus

A campus is by tradition the land on which a college or university and related institutional buildings are situated. Usually a college campus includes libraries, lecture halls, residence halls, student centers or dining halls, and park-like settings.

A modern campus is a collection of buildings and grounds that belong to a given institution, either academic or non-academic. Examples include the Googleplex and Apple Park.

Etymology
The word derives from a Latin word for "field" and was first used to describe the large field adjacent Nassau Hall of the College of New Jersey (now Princeton University) in 1774. The field separated Princeton from the small nearby town.

Some other American colleges later adopted the word to describe individual fields at their own institutions, but "campus" did not yet describe the whole university property. A school might have one space called a campus, another called a field, and still another called a yard.

History
The tradition of a campus began with the medieval European universities where the students and teachers lived and worked together in a cloistered environment. The notion of the importance of the setting to academic life later migrated to America, and early colonial educational institutions were based on the Scottish and English collegiate system.

The campus evolved from the cloistered model in Europe to a diverse set of independent styles in the United States. Early colonial colleges were all built in proprietary styles, with some contained in single buildings, such as the campus of Princeton University or arranged in a version of the cloister reflecting American values, such as Harvard's. Both the campus designs and the architecture of colleges throughout the country have evolved in response to trends in the broader world, with most representing several different contemporary and historical styles and arrangements.

Uses
The meaning expanded to include the whole university institutional property during the 20th century, with the old meaning persisting into the 1950s in some places.

Office buildings
In the early 1990s the term began to be used to describe a company's office building complex, most notably when Apple's Infinite Loop campus was first built, which at the time was exclusively for research and development. The Microsoft Campus in Redmond, Washington, is another example of this usage, although it was built in the 1980s, before the term was applied to company property. In the 21st century, hospitals and even airports sometimes use the term to describe the territory of their respective facilities.

Universities
The word campus has also been applied to European universities, although some such institutions (in particular, "ancient" universities such as Bologna, Padua, Oxford and Cambridge) are characterized by ownership of individual buildings in university town-like urban settings rather than sprawling park-like lawns in which buildings are placed.

title: Campus


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Crossbow

A crossbow is a ranged weapon using an elastic launching device consisting of a bow-like assembly called a prod, mounted horizontally on a main frame called a tiller, which is hand-held in a similar fashion to the stock of a long gun. Crossbows shoot arrow-like projectiles called bolts or quarrels. A person who shoots crossbow is called a crossbowman or an arbalist (after the arbalest, a European crossbow variant used during the 12th century).

Crossbows and bows use the same launch principle, but an archer using a longbow must maintain its draw by pinching the bowstring with fingers, pulling it back with arm and back muscles, and then holding that form while aiming, which demands significant physical strength. A crossbow has a locking mechanism to maintain the draw, limiting the shooter's exertion to pulling the string into the lock and then releasing the shot by depressing a trigger. This enables a crossbowman to handle more draw weight, and to hold it with significantly less physical strain, thus potentially achieving better precision and enabling their effective use by less-skilled personnel. Crossbows are usually drawn by direct pulling, but windlass-like mechanisms requiring less force were sometimes used.

The earliest known crossbows were made in the first millennium BC, as early as the 7th century BC in ancient China and as early as the 1st century AD in Greece (as the gastraphetes). Crossbows brought about a major shift in the role of projectile weaponry in wars, such as during Qin's unification wars and later Han campaigns against northern nomads and western states. The medieval European crossbow was called by many names, including "crossbow" itself; most of these names derived from the word ballista, an ancient Greek torsion siege engine similar in appearance but different in design principle.

In modern times, firearms have largely supplanted bows and crossbows as weapons of war, but crossbows remain widely used for competitive shooting sports and hunting, and for relatively silent shooting.

Terminology
A crossbowman or crossbow-maker is sometimes called an arbalista, arbalist, or arbalest. The last two are also used to refer to the crossbow.

Arrow, bolt, and quarrel are all suitable terms for crossbow projectiles.

The lath, also called the prod, is the bow of the crossbow. According to W.F. Peterson, the prod came into usage in the 19th century as a result of mistranslating rodd in a 16th-century list of crossbow effects.

The stock is the wooden body on which the bow is mounted, although the medieval tiller is also used.

The lock refers to the release mechanism, including the string, sears, trigger lever, and housing.

Construction
Noix corde carreau arbalette.svg crossbow nut mechanism: 1. Nut.

2. String.

3. Quarrel.

4. Trigger.]]

A crossbow is essentially a bow mounted on an elongated frame (called a tiller or stock) with a built-in mechanism that holds the drawn bow string, as well as a trigger mechanism, which is used to release the string.

Chinese vertical trigger lock
The Chinese trigger was a mechanism typically composed of three cast bronze pieces housed inside a hollow bronze enclosure. The entire mechanism is then dropped into a carved slot within the tiller and secured together by two bronze rods. The string catch (nut) is shaped like a "J" because it usually has a tall erect rear spine that protrudes above the housing, which serves the function of both a cocking lever (by pushing the drawn string onto it) and a primitive rear sight. It is held stationary against tension by the second piece, which is shaped like a flattened "C" and acts as the sear. The sear cannot move as it is trapped by the third piece, i.e. the actual trigger blade, which hangs vertically below the enclosure and catches the sear via a notch. The two bearing surfaces between the three trigger pieces each offers a mechanical advantage, which allow for handling significant draw weights with a much smaller pull weight. During shooting, the user will hold the crossbow at eye level by a vertical handle and aim along the arrow using the sighting spine for elevation, similar to how a modern rifleman shoots with iron sights. When the trigger blade is pulled, its notch disengages from the sear and allows the latter to drop downwards, which in turn frees up the nuts to pivot forward and release the bowstring.

European rolling nut lock
The earliest European designs featured a transverse slot in the top surface of the frame, down into which the string was placed. To shoot this design, a vertical rod is thrust up through a hole in the bottom of the notch, forcing the string out. This rod is usually attached perpendicular to a rear-facing lever called a tickler. A later design implemented a rolling cylindrical pawl called a nut to retain the string. This nut has a perpendicular centre slot for the bolt, and an intersecting axial slot for the string, along with a lower face or slot against which the internal trigger sits. They often also have some form of strengthening internal sear or trigger face, usually of metal. These roller nuts were either free-floating in their close-fitting hole across the stock, tied in with a binding of sinew or other strong cording; or mounted on a metal axle or pins. Removable or integral plates of wood, ivory, or metal on the sides of the stock kept the nut in place laterally. Nuts were made of antler, bone, or metal. Bows could be kept taut and ready to shoot for some time with little physical straining, allowing crossbowmen to aim better without fatiguing.

Bow
Chinese crossbow bows were made of composite material from the start.

European crossbows from the 10th to 12th centuries used wood for the bow, also called the prod or lath, which tended to be ash or yew.

Composite bows started appearing in Europe during the 13th century and could be made from layers of different material, often wood, horn, and sinew glued together and bound with animal tendon. These composite bows made of several layers are much stronger and more efficient in releasing energy than simple wooden bows.

As steel became more widely available in Europe around the 14th century, steel prods came into use.

Traditionally, the prod was often lashed to the stock with rope, whipcord, or other strong cording. This is called the bridle

Spanning mechanism
The Chinese used winches for large crossbows mounted on fortifications or wagons, known as "bedded crossbows" (床弩). Winches may have been used for handheld crossbows during the Han dynasty (202 BC–9 AD, 25–220 AD), but there is only one known depiction of it. The 11th century Chinese military text Wujing Zongyao mentions types of crossbows using winch mechanisms, but it is not known if these were actually handheld crossbows or mounted crossbows. Another drawing method involved the shooters sitting on the ground, and using the combined strength of leg, waist, back and arm muscles to help span much heavier crossbows, which were aptly called "waist-spun crossbows" (腰張弩).

During the medieval era, both Chinese and European crossbows used stirrups as well as belt hooks. In the 13th century, European crossbows started using winches, and from the 14th century an assortment of spanning mechanisms such as winch pulleys, cord pulleys, gaffles (such as gaffe levers, goat's foot levers, and rarer internal lever-action mechanisms), cranequins, and even screws.

Variants

The smallest crossbows are pistol crossbows. Others are simple long stocks with the crossbow mounted on them. These could be shot from under the arm. The next step in development was stocks of the shape that would later be used for firearms, which allowed better aiming. The arbalest was a heavy crossbow that required special systems for pulling the sinew via windlasses. For siege warfare, the size of crossbows was further increased to hurl large projectiles, such as rocks, at fortifications. The required crossbows needed a massive base frame and powerful windlass devices.

Projectiles

The arrow-like projectiles of a crossbow are called bolts or quarrels. These are usually much shorter than arrows but can be several times heavier. There is an optimum weight for bolts to achieve maximum kinetic energy, which varies depending on the strength and characteristics of the crossbow, but most could pass through common mail. Crossbow bolts can be fitted with a variety of heads, some with sickle-shaped heads to cut rope or rigging; but the most common today is a four-sided point called a quarrel. A highly specialized type of bolt is employed to collect blubber biopsy samples used in biology research.

Even relatively small differences in arrow weight can have a considerable impact on its flight trajectory and drop.

Bullet-shooting crossbows are modified crossbows that use bullets or stones as projectiles.

Accessories

The ancient Chinese crossbow often included a metal (i.e. bronze or steel) grid serving as iron sights. Modern crossbow sights often use similar technology to modern firearm sights, such as red dot sights and telescopic sights. Many crossbow scopes feature multiple crosshairs to compensate for the significant effects of gravity over different ranges. In most cases, a newly bought crossbow will need to be sighted for accurate shooting.

A major cause of the sound of shooting a crossbow is vibration of various components. Crossbow silencers are multiple components placed on high vibration parts, such as the string and limbs, to dampen vibration and suppress the sound of loosing the bolt.

China

In terms of archaeological evidence, crossbow locks made of cast bronze have been found in China dating to around 650 BC. They have also been found in Tombs 3 and 12 at Qufu, Shandong, previously the capital of Lu, and date to the 6th century BC. Bronze crossbow bolts dating from the mid-5th century BC have been found at a Chu burial site in Yutaishan, Jiangling County, Hubei Province. Other early finds of crossbows were discovered in Tomb 138 at Saobatang, Hunan Province, and date to the mid-4th century BC. It is possible that these early crossbows used spherical pellets for ammunition. A Western Han mathematician and music theorist, Jing Fang (78–37 BC), compared the moon to the shape of a round crossbow bullet. The Zhuangzi also mentions crossbow bullets.

The earliest Chinese documents mentioning a crossbow were texts from the 4th to 3rd centuries BC attributed to the followers of Mozi. This source refers to the use of a giant crossbow between the 6th and 5th centuries BC, corresponding to the late Spring and Autumn period. Sun Tzu's The Art of War (first appearance dated between 500 BC to 300 BC ) refers to the characteristics and use of crossbows in chapters 5 and 12 respectively, and compares a drawn crossbow to "might". The Huainanzi advises its readers not to use crossbows in marshland where the surface is soft and it is hard to arm the crossbow with the foot. The Records of the Grand Historian, completed in 94 BC, mentions that Sun Bin defeated Pang Juan by ambushing him with a battalion of crossbowmen at the Battle of Maling in 342 BC. The Book of Han, finished 111 AD, lists two military treatises on crossbows.

Handheld crossbows with complex bronze trigger mechanisms have also been found with the Terracotta Army in the tomb of Qin Shi Huang (r. 221–210 BC) that are similar to specimens from the subsequent Han dynasty (202 BC–220 AD), while crossbowmen described in the Qin and Han dynasty learned drill formations, some were even mounted as charioteers and cavalry units, and Han dynasty writers attributed the success of numerous battles against the Xiongnu and Western Regions city-states to massed crossbow volleys. The bronze triggers were designed in such a way that they were able to store a large amount of energy within the bow when drawn but was easily shot with little resistance and recoil when the trigger was pulled. The trigger nut also had a long vertical spine that could be used like a primitive rear sight for elevation adjustment, which allowed precision shooting over longer distances. The Qin and Han dynasty-era crossbow was also an early example of a modular design, as the bronze trigger components were also mass-produced with relative precise tolerances so that the parts were interchangeable between different crossbows. The trigger mechanism from one crossbow can be installed into another simply by dropping into a tiller slot of the same specifications and secured with dowel pins. Some crossbow designs were also found to be fitted with bronze buttplates and trigger guard.

It is clear from surviving inventory lists in Gansu and Xinjiang that the crossbow was greatly favored by the Han dynasty. For example, in one batch of slips there are only two mentions of bows, but thirty mentions of crossbows. Crossbows were mass-produced in state armories with designs improving as time went on, such as the use of a mulberry wood stock and brass. Such crossbows during the Song Dynasty in 1068 AD could pierce a tree at 140 paces. Crossbows were used in numbers as large as 50,000 starting from the Qin dynasty and upwards of several hundred thousand during the Han. According to one authority, the crossbow had become "nothing less than the standard weapon of the Han armies", by the second century BC. Han soldiers were required to arm a crossbow with a draw weight equivalent of 76 kg to qualify as an entry-level crossbowman, while it was claimed that a few elite troops were capable of arming crossbows with a draw-weight in excess of 340 kg by the hands-and-feet method.

After the Han dynasty, the crossbow lost favor during the Six Dynasties, until it experienced a mild resurgence during the Tang dynasty, under which the ideal expeditionary army of 20,000 included 2,200 archers and 2,000 crossbowmen. Li Jing and Li Quan prescribed 20 percent of the infantry to be armed with crossbows.

During the Song dynasty, the crossbow received a huge upsurge in military usage, and often overshadowed the bow 2 to 1 in numbers. During this time period, a stirrup was added for ease of loading. The Song government attempted to restrict the public use of crossbows and sought ways to keep both body armor and crossbows out of civilian ownership. Despite the ban on certain types of crossbows, the weapon experienced an upsurge in civilian usage as both a hunting weapon and pastime. The "romantic young people from rich families, and others who had nothing particular to do" formed crossbow-shooting clubs as a way to pass time.

During the late Ming dynasty, no crossbows were mentioned to have been produced in the three-year period from 1619 to 1622. With 21,188,366 taels, the Ming manufactured 25,134 cannons, 8,252 small guns, 6,425 muskets, 4,090 culverins, 98,547 polearms and swords, 26,214 great "horse decapitator" swords, 42,800 bows, 1,000 great axes, 2,284,000 arrows, 180,000 fire arrows, 64,000 bow strings, and hundreds of transport carts.

Military crossbows were armed by treading, or basically placing the feet on the bow stave and drawing it using one's arms and back muscles. During the Song dynasty, stirrups were added for ease of drawing and to mitigate damage to the bow. Alternatively, the bow could also be drawn by a belt claw attached to the waist, but this was done lying down, as was the case for all large crossbows. Winch-drawing was used for the large mounted crossbows as seen below, but evidence for its use in Chinese hand-crossbows is scant.

There were also other sorts of crossbows, such as the repeating crossbow, multi-shot crossbow, and larger field artillery crossbows.

Southeast Asia

Around the third century BC, King An Dương of Âu Lạc (modern-day northern Vietnam) and (modern-day southern China) commissioned a man named Cao Lỗ (or Cao Thông) to construct a crossbow and christened it "Saintly Crossbow of the Supernaturally Luminous Golden Claw" (nỏ thần), which could kill 300 men in one shot. According to historian Keith Taylor, the crossbow, along with the word for it, seems to have been introduced into China from Austroasiatic peoples in the south around the fourth century BC. However, this is contradicted by crossbow locks found in ancient Chinese Zhou dynasty tombs dating to the 600s BC.

In 315 AD, Nu Wen taught the Chams how to build fortifications and use crossbows. The Chams would later give the Chinese crossbows as presents on at least one occasion.

Crossbow technology for crossbows with more than one prod was transferred from the Chinese to Champa, which Champa used in its invasion of the Khmer Empire's Angkor in 1177. When the Chams sacked Angkor they used the Chinese siege crossbow. The Chinese taught the Chams how to use crossbows and mounted archery Crossbows and archery in 1171. The Khmer also had double-bow crossbows mounted on elephants, which Michel Jacq-Hergoualc'h suggests were elements of Cham mercenaries in Jayavarman VII's army.

The native Montagnards of Vietnam's Central Highlands were also known to have used crossbows, as both a tool for hunting, and later an effective weapon against the Viet Cong during the Vietnam War. Montagnard fighters armed with crossbows proved a highly valuable asset to the US Special Forces operating in Vietnam, and it was not uncommon for the Green Berets to integrate Montagnard crossbowmen into their strike teams.

Ancient Greece

The earliest crossbow-like weapons in Europe probably emerged around the late 5th century BC when the gastraphetes, an ancient Greek crossbow, appeared. The name means "belly-bow"; the concave withdrawal rest at one end of the stock was placed against the belly of the operator, and he could press it to withdraw the slider before attaching a string to the trigger and loading the bolt; this could store more energy than Greek bows. The device was described by the Greek author Heron of Alexandria in his Belopoeica ("On Catapult-making"), which draws on an earlier account of his compatriot engineer Ctesibius (fl. 285–222 BC). According to Heron, the gastraphetes was the forerunner of the later catapult, which places its invention some unknown time prior to 399 BC. The gastraphetes was a crossbow mounted on a stock divided into a lower and upper section. The lower was a case fixed to the bow, and the upper was a slider which had the same dimensions as the case. It was used in the Siege of Motya in 397 BC. This was a key Carthaginian stronghold in Sicily, as described in the 1st century AD by Heron of Alexandria in his book Belopoeica.

There were also other arrow-shooting machines such as the larger ballista and smaller Scorpio from around 338 BC, but these are torsion catapults and are not considered crossbows. Arrow-shooting machines (katapeltai) are briefly mentioned by Aeneas Tacticus in his treatise on siegecraft written around 350 BC. An Athenian inventory from 330 to 329 BC includes catapults bolts with heads and flights. Arrow-shooting machines in action are reported from Philip II's siege of Perinthos in Thrace in 340 BC. At the same time, Greek fortifications began to feature high towers with shuttered windows in the top, presumably to house anti-personnel arrow shooters, as in Aigosthena.

Ancient Rome

The late 4th century author Vegetius, in his De Re Militari, describes arcubalistarii (crossbowmen) working together with archers and artillerymen. However, it is disputed whether arcuballistas were crossbows or torsion-powered weapons. The idea that the arcuballista was a crossbow is due to Vegetius referring separately to it and the manuballista, which was torsion powered. Therefore, if the arcuballista was not like the manuballista, it may have been a crossbow. According to Vegetius, these were well-known devices, and hence he did not describe them in depth. Joseph Needham argues against the existence of Roman crossbowmen:

On the other hand, Arrian's earlier Ars Tactica, from about 136 AD, also mentions 'missiles shot not from a bow but from a machine' and that this machine was used on horseback while in full gallop. It is presumed that this was a crossbow.

The only pictorial evidence of Roman arcuballistas comes from sculptural reliefs in Roman Gaul depicting them in hunting scenes. These are aesthetically similar to both the Greek and Chinese crossbows, but it is not clear what kind of release mechanism they used. Archaeological evidence suggests they were similar to the rolling nut mechanism of medieval Europe.

Medieval Europe

There are essentially no references to the crossbow in Europe from the 5th until the 10th century. There is however a depiction of a crossbow as a hunting weapon on four Pictish stones from early medieval Scotland (6th to 9th centuries): St. Vigeans no. 1, Glenferness, Shandwick, and Meigle.

The crossbow reappeared again in 947 as a French weapon during the siege of Senlis and again in 984 at the siege of Verdun. Crossbows were used at the battle of Hastings in 1066, and by the 12th century they had become common battlefield weapons. The earliest extant European crossbow remains were found at Lake Paladru, dated to the 11th century.

The crossbow superseded hand bows in many European armies during the 12th century, except in England, where the longbow was more popular. Later crossbows (sometimes referred to as arbalests), utilizing all-steel prods, were able to achieve power close (and sometime superior) to longbows, but were more expensive to produce and slower to reload because they required the aid of mechanical devices such as the cranequin or windlass to draw back their extremely heavy bows. Usually these could only shoot two bolts per minute versus twelve or more with a skilled archer, often necessitating the use of a pavise (shield) to protect the operator from enemy fire. Along with polearm weapons made from farming equipment, the crossbow was also a weapon of choice for insurgent peasants such as the Taborites. Genoese crossbowmen were famous mercenaries hired throughout medieval Europe, while the crossbow also played an important role in anti-personnel defense of ships.

Crossbows were eventually replaced in warfare by gunpowder weapons. Early hand cannons had slower rates of fire and much worse accuracy than contemporary crossbows, but the arquebus (which proliferated in the mid to late 15th century) matched crossbows' rate of fire while being far more powerful. The Battle of Cerignola in 1503 was won by Spain largely through the use of matchlock arquebuses, marking the first time a major battle was won through the use of hand-held firearms. Later, similar competing tactics would feature harquebusiers or musketeers in formation with pikemen, pitted against cavalry firing pistols or carbines. While the military crossbow had largely been supplanted by firearms on the battlefield by 1525, the sporting crossbow in various forms remained a popular hunting weapon in Europe until the eighteenth century. Crossbows saw irregular use throughout the rest of the 16th century; for example, Maria Pita's husband was killed by a crossbowman of the English Armada in 1589.

Islamic world
There are no references to crossbows in Islamic texts earlier than the 14th century. Arabs in general were averse to the crossbow and considered it a foreign weapon. They called it qaus al-rijl (foot-drawn bow), qaus al-zanbūrak (bolt bow) and qaus al-faranjīyah (Frankish bow). Although Muslims did have crossbows, there seems to be a split between eastern and western types. Muslims in Spain used the typical European trigger, while eastern Muslim crossbows had a more complex trigger mechanism.

Mamluk cavalry used crossbows.

Elsewhere and later
Oyumi were ancient Japanese artillery pieces that first appeared in the seventh century (during the Asuka period). According to Japanese records, the Oyumi was different from the handheld crossbow also in use during the same time period. A quote from a seventh-century source seems to suggest that the Oyumi may have able to fire multiple arrows at once: "the Oyumi were lined up and fired at random, the arrows fell like rain". A ninth-century Japanese artisan named Shimaki no Fubito claimed to have improved on a version of the weapon used by the Chinese; his version could rotate and fire projectiles in multiple directions. The last recorded use of the Oyumi was in 1189.

In West and Central Africa, crossbows served as a scouting weapon and for hunting, with African slaves bringing this technology to natives in America. In the Southern United States, the crossbow was used for hunting and warfare when firearms or gunpowder were unavailable because of economic hardships or isolation. In the north of Northern America, light hunting crossbows were traditionally used by the Inuit. These are technologically similar to the African-derived crossbows, but have a different route of influence.

Spanish conquistadors continued to use crossbows in the Americas long after they were replaced in European battlefields by firearms. Only in the 1570s, did firearms become completely dominant among the Spanish in the Americas.

The French and the British used a crossbow-like Sauterelle (French for grasshopper) in World War I. It was lighter and more portable than the Leach Trench Catapult, but less powerful. It weighed 24 kg and could throw an F1 grenade or Mills bomb 110 - 140 m. The Sauterelle replaced the Leach Catapult in British service and was in turn replaced in 1916 by the 2-inch Medium Trench Mortar and Stokes mortar. Early in the war actual crossbows were pressed into service in small numbers by both French and German troops to launch grenades.

A range of crossbows were developed by the Allied powers during the Second World War for assassinations and covert operations, but none appear to have ever been used in the field. A small number of crossbows were built and used by Austrialain forces in the New Guinea campaign.

Hunting, leisure, and science
Crossbows are used for shooting sports and bowhunting in modern archery and for blubber biopsy samples in scientific research. In some countries such as Canada, they may be less heavily regulated than firearms, and thus more popular for hunting; some jurisdictions have bow and/or crossbow only seasons.

Military and paramilitary
Crossbows are no longer used in battles, but they are still used in some military applications. For example, there is an undated photograph of Peruvian soldiers equipped with crossbows and rope to establish a zip-line in difficult terrain. In Brazil, the CIGS (Jungle Warfare Training Center) also trains soldiers in the use of crossbows.

In the United States, SAA International Ltd manufacture a 200 J crossbow-launched version of the U.S. Army type classified Launched Grapnel Hook (LGH), among other mine countermeasure solutions designed for the Middle Eastern theatre. It was evaluated as successful in Cambodia and Bosnia. It is used to probe for and detonate tripwire-initiated mines and booby traps at up to 50 m. The concept is similar to the LGH device originally fired from a rifle, as a plastic retrieval line is attached. Reusable up to 20 times, the line can be reeled back in without exposing the user. The device is of particular use in tactical situations where noise discipline is important.

In Europe, Barnett International sold crossbows to Serbian forces which, according to The Guardian, were later used "in ambushes and as a counter-sniper weapon" against the Kosovo Liberation Army during the Kosovo War in the areas of Pec and Djakovica, south west of Kosovo. Whitehall launched an investigation, though the Department of Trade and Industry established that not being "on the military list", crossbows were not covered by export restrictions. Paul Beaver of Jane's Defence Publications commented that, "They are not only a silent killer, they also have a psychological effect". On 15 February 2008, Serbian Minister of Defence Dragan Sutanovac was pictured testing a Barnett crossbow during a public exercise of the Serbian Army's Special Forces in Nis, 200 km south of Belgrade. Special forces in both Greece and Turkey also continue to employ the crossbow. Spain's Green Berets still use the crossbow as well.

In Asia, some Chinese armed forces use crossbows, including the special force Snow Leopard Commando Unit of the People's Armed Police and the People's Liberation Army. One reason for this is the crossbow's ability to stop persons carrying explosives without risk of causing detonation. During the Xinjiang riots of July 2009, Crossbows were used by security forces to suppress rioters. The Indian Navy's Marine Commando Force were equipped until the late 1980s with crossbows with cyanide-tipped bolts, as an alternative to suppressed handguns.

Comparison to conventional bows
With a crossbow, archers could release a draw force far in excess of what they could have handled with a bow. Furthermore, the crossbow could hold the tension indefinitely, whereas even the strongest longbowman could only hold a drawn bow for a short time. The ease of use of a crossbow allows it to be used effectively with little training, while other types of bows take far more skill to shoot accurately. The disadvantage is the greater weight and clumsiness to reload compared to a bow, as well as the slower rate of shooting and the lower efficiency of the acceleration system, but there would be reduced elastic hysteresis, making the crossbow a more accurate weapon.

Medieval European crossbows had a much smaller draw length than bows, so that, for the same energy to be imparted to the projectile, the crossbow had to have a much higher draw weight.

A direct comparison between a fast hand-drawn replica crossbow and a longbow show a 6:10 rate of shooting or a 4:9 rate within 30 seconds and comparable weapons.

Legislation

Today, the crossbow often has a complicated legal status due to the possibility of lethal use and its similarities to both firearms and bows. While some jurisdictions treat crossbows in the same way as firearms, many others do not require any sort of license to own a crossbow. The legality of using a crossbow for hunting varies widely in different jurisdictions.

title: Crossbow