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Iranian History/The Seleucids

The Achaemenid Empire fell with the defeat of Darius III at Arbela and the conquest of the Empire. A pretender rose to the throne calling himself Artaxerxes V but he was captured by Alexander and killed. With this Achaemenid rule came to an end and the country was taken over by the Greeks. Two Greek dynasties ruled Persia one after the another for a period of hundred years. They were eventually displaced by the rising Parthian power which drove the Seleucids the last of the two dynasties west into Syria and established its own rule in Persepolis.

Alexander III or Alexander the Great 331 - 323 BC
Alexander the Great or Alexander III of Macedon became overlord of all Persia on the defeat of Darius III Condomannus at the Battle of Arbela. Darius III fled the battlefield and was captured and killed by the eunuch Bessas who ascended the throne assuming the title Artaxerxes V. But soon afterwards, Alexander invaded Persepolis and burnt down the city. Artaxerxes V was captured and punished with death for having caused the dead of Darius III. Later, Alexander gave a royal funeral to Darius III and married one of his daughters.

Alexander did not spend enough time at Persepolis to consolidate his hold on the Empire. Immediately after proclaiming himself as the Shah of Persia, he left for the East on a conquering spree taking the eastern satraps of Gandhara, Bactria,the Swat Valley and the Punjab. In Punjab, he encountered the Indian ruler Porus and defeated him but did not proceed further into Indian territory and was obliged to return. He died in 323 BC at Babyon. The cause is not known, but food poisoning is suspected.

The administrative structure of the Achaemenids remained largely intact all through Alexander's rule. The Persian satraps governed the satrapies for their Greek overlords. And Alexander did not distinguish between Persians and Greeks in Government service. He tried to foster close friendly relations between the Persians and the Greeks and encouraged Greek soldiers to intermarry with native women.

However, orthodox Zoroastrians remembered Alexander's period of rule for the tyranny he unleashed on Zoroastrianism and Zoroastrians. Being a polytheist himself, it is believed that he despised monotheistic religions and ordered the Avesta to be destroyed in its entirety. Zoroastrian scriptures mention him as "the ally of the Evil One". His invasion is believed to be the first ever cataclysm which befell Zoroastrianism the second one being the invasion of the Arabs. The Shahnameh casts an aura of divinity about him by nurturing fantastical legends and unfounded rumors about Alexander actually being the son of Darius III and a daughter of Philip of Macedon who was smuggled to Macedon in his infancy and brought up in the custody of his grandfather in order to conceal the true identity of his parents. But there is no available historical evidence to substantiate this claim. Nevertheless, Alexander left behind a legacy of destruction and intolerance which Zoroastrians found difficult to forget or forgive for centuries to come.

Alexander IV 323 - 309 BC
On the unexpectedly early death of Alexander in 323 BC, the Crown passed to his still yet unborn son who later ascended the throne as Alexander IV. Alexander IV was the last ruler of the united Macedonian Empire. The kingdom, however, was torn apart by anarchy and civil war. With an incompetent minor on the throne, the distant outlying provinces became the target of adventurers and claimants to the throne.

On the death of Alexander IV in 309 BC, the kingdom broke into three parts -- the European provinces of the Empire were under the hereditary royal line of Macedonian kings who maintained an uninterrupted succession from Alexander the Great; the Asian provinces which comprised over three-fourths of the Empire became independent under Seleucus I Nikator a general of Alexander the Great who established the Seleucid Dynasty while the African provinces of the Empire comprising mostly of Egypt became independent under the Greek Ptolemies.

The Seleucids
When Alexander's kingdom disintegrated a few years after his death, Persia came under the rule of Seleucus I Nikator, a general of Alexander. Seleucus Nikator and his successors the Seleucids ruled Persia from 320 BC till 250 BC when most of Persia became independent under Parthian rule. The remainder was snatched away from Seleucids in stages from 250 BC to 171 BC. By the end of the 2nd century BC, the authority of the Seleucids over Persia had vanished. However, the Seleucids continued to rule over Syria till 65 BC when a Roman invasion of Syria wiped away the last remnants of Greek imperialism.

Seleucus I Nikator 320 - 281 BC
Seleucus I or Seleucus Nikator a general of Alexander was made satrap of Babylon on the second division of the Empire in 320 BC. In the struggle between Antigonus and Eumenes for sovereignty he supported Antigonus against his rival. But strangely, this only invoked the jealousy of Antigonus instead of his gratitude and he schemed to do away with Seleucus. Hence, Seleucus was forced to flee and he fled to the court of Ptolemy of Egypt who offered him protection. Meanwhile,the conduct of Antigonus had made a lot of enemies and ultimately culminated in the Battle of Ipsus (301 BC) in which "the Allies" inflicted a crushing defeat upon him. Seleucus was one of the first to rebel and he was locked in a dreadful confrontation with Antigonus ever since the recovery of Babylon in 312 BC. He led the bulk of the troops in the Battle of Issus as a consequence of which he was recognized as the independent overlord of all the Greek conquests in Asia.

Soon after obtaining his independence, Seleucus seems to have organized an invasion of India. Seleucus wanted to annex the lands to the east of the Indus which Alexander had failed to conquer. But Seleucus faced a stout resistance from the emerging Mauryan power which successfully blocked his advance. Chandragupta Maurya (the Sandrocottus of the Greeks), the Mauryan king pushed back the Greek troops to the other side of the Indus and conquered Afghanistan. The war came to an abrupt end and peace was concluded. As per the terms of the peace, Pakthoonistan, eastern Afghanistan, Bactria, Baluchistan and parts of Sistan were made over to Chandragupta Maurya in return for a princely gift of 500 war elephants. A marital alliance was sealed between the two with the marriage of Seleucus' daughter Helen with Chandragupta Maurya. Megasthenes was sent as the Greek ambassador to the Indian court and he has described the splendors of the Mauryan capital Pataliputra (Greek:Palimbothra) in his book Indica.

During the initial years of his reign, Babylon was the capital of the Empire. But in 301 BC, he constructed the city of Selucia-upon-the-Tigris and moved the capital to that city. After the Battle of Ipsus, he once again shifted his capital and moved the seat of his Government to the city of Antioch in Syria. Antioch was to remain the capital of Seleucus Nikator and his successors till the end of the Seleucid Empire.

Selecus I died in 281 BC and was succeeded by his son Antiochus I.

Antiochus I (Soter) 281 - 261 BC
Antiochus I ruled from 281 BC to 261 BC. He was involved in constant warfare with the kings of the west. He invaded the kingdom of Bithynia in Turkey during the reigns of Zipcetas and Nicomedes I. Antiochus I found it difficult to subjugate Bithynia as Nicomedes was aided by the Gauls. Finally, the wars ended on an indecisive note. In 263 BC, he attacked Eumenes of Pergamus but was defeated at Sardis. He also launched a massive invasion of Egypt to support the rebelling Cyrenes against the Ptolemaic ruler but was once again unsuccessful. Both Antiochus I and II were preoccupied with their wars in the West that they paid little attention to the east. Ultimately the level of neglect reached such alarming proportions during the reign of Antiochus II that a full-scale revolution broke in Parthia which was not put down in time. This resulted in the formation of the Parthian Empire and started the process of dismemberment of Greek rule in Persia.

Antiochus II (Theus) 261 - 249 BC
Antiochus I died in 261 BC and was succeeded by Antiochus II. Soon after his accession to the throne, he indulged in war with Ptolemy Philadelphus of Egypt. In 260 BC, he deposed Timachus, the tyrant of the country of Miletus thereby provoking Egypt into war. The bwar lasted over a decade until peace was concluded at the fag end of Antiochus Theus' reign. But by then, Antiochus had lost the satrapies of Parthia and Bactria which had broke off between 256 and 250 BC when Antiochus was occupied in an intense struggle with Egypt apart from indulging in hostilies with Atropatene. He made no attempt to recover then. He died soon after the war came to an end.

Decline of the Seleucids and the Rise of Parthia
In 256 BC, when Antiochus II was busy in his wars, the Greek satrap of Bactria (the Persian Baktri or modern-day Balkh in Afghanistan) Diodotus declared his independence. Sometime between 256 and 250 BC, Arsaces(Arshaka) an inhabitant of Parthia revolted and established the Parthian kingdom. The Parthian kingdom gradually rose from strength to strength displacing the Seleucid Empire over a period of time. Antiochus II died soon after the war in Egypt came to an end.

Antiochus II was succeeded by his son Seleucus II during whose reign Ptolemy Euergetes the ruler of Egypt invaded the kingdom and occupied Antioch. Seleucus II ruled as a feudatory of Ptolemy who penetrated the kingdom upto its Eastern frontiers and threatened to revive the mighty empire of Alexander the Great. But a rebellion in Egypt cut short his enterprise thereby sparing both Seleucus II and the emerging Parthian kingdom from destruction.

In 237 BC, Seleucus II allied with his brother Antiochus Hierax and invaded Parthia to recover lost territory. But the alliance soon broke off and Tiridates the Parthian monarch administered a crushing defeat on Seleucus II in the battle that ensued. For the next twenty years, Seleucus II concentrated his energies on quelling the rebellion of his brother Antiochus Hierax that he allowed Tiridates to go scott free.

In 214 BC, another jolt was administered to the crumbling Seleucid Empire when taking advantage of a civil war between Antiochus III the son of Seleucus II and Emperor of Syria and Achseus a rebel satrap the Parthian king Artabanus invaded the tract of Media and annexed it to his empire. No sooner had he quelled the rebellion by Achseus that Antiochus III turned his attention to Parthia and invaded the kingdom. The capital of the Parthian Empire Hecatompylos was occupied and Artabanus the Parthian monarch was forced to flee. At length, Artabanus submitted and was permitted to rule as a satrap of Syria. Soon after the successful war against Parthia, Antiochus III proceeded further eastward and subdued Bactria.

Syria had a minor revival during the reign of Antiochus III also called Antiochus the Great but the decline commenced once again after his death. During the reign of Seleucus IV (Philopater) who ruled from 181 to 174 BC, the Parthian monarch Phraates occupied Media and Rhagai. As a result ,the Seleucid kingdom was cut off from its eastern territories. Seleucus IV was succeeded by his brother Antiochus IV Epiphanes in 174 BC. Epiphanes earned the detestable reputation of being a religious fanatic who tried to force Hellenistic polytheism upon monotheistic Jews of Palestine. During his reign, Egypt claimed Palestine and a battle was fought with Egypt from 171 to 168 BC. It was brought to an end only by the inference of Rome which asked Syria to cede all occupied territories to Egypt. Epiphanes made a successful conquest of Armenia in 165 BC but troubles began to brew in the home-front due to his policy of religious intolerance and destruction of Zoroastrian temples. Epiphanes died in 164 BC and was succeeded by a lad of nine. The boy Antiochus Eupator was deposed a few years later by a rival contender Demetrius who ascended the throne. A few years later Media was conquered by the Parthian monarch Mithridates. In 140 BC, the Seleucid monarch Demetrius II invaded Parthia with the hope of recovering lost provinces but was caught off-guard and captured by Mithridates who took him prisoner.

Antiochus Sidetus was crowned Emperor in 140 BC in the absence of Demetrius II. He fought the pretender Tryphon and punished him with death in the year 137 BC. He then turned his attention to Palestine and subdued the province by 133 BC. By 129 BC he was well-prepared for an invasion of Parthia. Collecting over 120,000 soldiers Sidetus crossed the frontier and invaded the Parthian Empire. The border provinces of Parthia fed-up with an oppressive administration openly welcomed the invader. However, winter impeded the progress of the army and following his instinct, Sidetus split up his army into several units and settled the towns of Mesapotamia. Phraates the Parthian Emperor saw his chance and sent Demetrius with a large Parthian army to reclaim the throne. The inhabitants were displeased with the haughty nature of the Greek soldiers and conspired a plot to cut down Sidetus' army in league with Phraates. Accordingly, on an appointed day, the inhabitants of Mesopotamia rose against the Seleucid soldiers camped inn their province and massacred all of them. The Parthian army pursued the remainder of the Seleucid army back into Syria. Sidetus was killed on the way and was succeeded by Demetrius. This was the last time that a Seleucid ruler dared to invade the Parthian Empire. The Seleucid Empire did survive till 65 BC but its power was greatly reduced and its influence felt only in Syria. In 65 BC, a Roman invasion of Syria put an end to the struggling Seleucid kingdom.

title: Iranian History/The Seleucids


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Iranian History/Qobad I and the Two Khusros 488 - 628 AD

Qobad I (First reign) 488 - 498
When Balash died in 488, civil war broke out. Qobad, a son of Firuz, entered the Persian capital with an army of Huns and captured the throne.

Qobad's actual Persian name seems to have been Kavadh which has been Arabized to Qobad. Immediately on ascending thehrone, he fought back the Khazars who had invaded the country. He resisted them with an army of over one hundred thousand men and drove them back across the fromntier. He also built fortified posts a;ong the northern frontier to protect the kingdom.

Around this time, Qobad came under the influence of one Mazdak which proved to be detrimental to his future. He tried to impose Mazdakism upon the country and had to face vehement protest from the Zoroastrian mobeds. The imposition of Mazdakism as the state religion was the last straw. Christian Armenia rebelled and broke off its allegiance to Persia when compelled to adopt MaZdakism. Vatian was appointed king of Armenia.

Eventually, a rebellion of the Persian populace placed power in the hands of the Magi who immediately deposed him and placed Jamasp upon the throne of Persia.

Jamasp 498 - 501
The crown was placed upon Jamasp's head immediately after Qobad had fled the kingdom. Jamasp was a man of peaceful disposition and did not fight any wars.

In 501, three years after Jamasp had been crowned king, Qobad returned at the head of 30,000 Hephthalite horsemen and demanded that the kingdom be reinstated unto him. Jamasp obliged and abdicated in favor of Qobad.

Qobad I (Second reign) 501 - 531
Immediately after commencing his second reign, Qobad I turned against the Mazdakites and organized a series of persecutions. This won him the sanction of the Magi who were responsible for deposing him earlier.

War Against Rome
As per the peace of 442, Rome was required to pay a certain amount of money for the upkeep of the fortresses along the border. However, Rome refused. Provoked, Qobad invaded Roman Armenia and captured Theodosiopolis. He then proceeded to ravage Roman Armenia and Roman Mesapotamia taking the impregnable fortress of Amida and plundering Arzanne. A party of Romans encountered a body of 800 Huns who fought in support of Persia and slaughtered it to the last man. However, they were surprised by a contingent of Persian troops nearby and had to pay the price. At this instant, as war was raging in all its fury, a Hephthalite invasion compelled Qobad to call off the invasion. The Romans recovered all the lost provinces. Peace was concluded between the warring forces and Rome agreed to pay the required amount of money for the upkeep of the frontier garrisons.

War Against the Huns
The campaign against the Huns occupied Qobad uninterruptedly for the next ten years. Rome triend to make most of the situation by strengthening its frontier garrisons. The war against the Huns came to an end only in 517.

In 517, when the battle against the Huns came to an end Qobad made a formal complaint against Constantinople. The Romans did not apologize but made professions of friendship. The Roman Emperor Justin concluded a treaty with the Huns and with Lazica to forge an alliance against Persia. The uneasy condition prevailed till the end of Qobad's reign but did not aggravate into full-fledged war.

Persecution of the Mazdakites
In 523, there came to light, a conspiracy to remove Qobad's son Khusro and replace him with another son of Qobad, a Mazdakite sympathizer named Phthasarus to the throne. Qobad was overcome by rage and instructed Khusro to destroy Mazdak and his cult in the Empire. The prince accordingly unleashed a reign of terror which put an end to Mazdakism. Mazdakism, however, did survive in a much reduced form till the Islamic conquests and even after. It is considered to be one of the major factors which inspired the nationalist Khoramdin movement against Arab rule.

Second War with Rome
In 523, Gurgenes the king of Iberia whom Qobad had pressurized to accept Zoroastrianism broke into open revolt. Qobad responded by dispatching a large army which quelled the rebellion and carried the war far into Roman territory. Rome retaliated by invading Persarmenia and Mesapotamia in 526. Two Roman contingents were sent against Persia both of which were defeated. In early 528, Belisarius the Roman commander was ordered to build a fort on the Persian border at Mindon but Qobad sent an army of 30,000 men against him whic spoiled his efforts.

Shortly afterwards, Belisarius was made 'Commander of the East'. He fought 50,000 Persian soldiers commanded by Mihran and utterly routed them. The Romans were also victorious in Armenia where Mermeroes the Persian general had to face defeat.

In 531, Al Mondar or Alamandarus the sheikh of the Arabs concluded an alliance with Persia. A joint Perso-Arab army was sent under Azarethes against the Romans. Belisarius quitted Daras but was defeated on the banks of the Euphrates and forced to flee.

Qobad did not survive for long after the completion of the Perso-Roman war. He died on September 12, 531 at the age of eighty-two and was succeeded by his son, Khusro Anushirvan or Khusro I.

Khusro I (Anushirvan) 531 - 578
Khusro Anushirvan ascended the throne in 531 after disposing off the rival contenders to the throne. On ascending the throne, he even went one stop further by eliminating the entire male line of Qobad I.

As soon as he ascended the throne, he concluded what has been termed hy historians as the "endless peace with Rome". While the peace was in vogue, the Roman Emperor Justinian was busy tackling the barbarian hordes which invaded his empire. Belisarius, especially, distinguished himself in these campaigns, emerging as the greatest general of the day. In 539, the defeated Ostrogoth king of Italy appealed to Khusro for help and Khusro responded by besieging Antioch thereby triggering the First Roman War of his reign.

First Roman War
Khusro Anushirvan invaded Antioch and reduced the citizens to utter desperation. However, he spared the city when the inhabitants agreed to pay a huge ransom. Khusro then passed north of Antioch and plundered Seleucia, Apameia and CHalcis before crossing the Euphrates into Mesapotamia and attacking Edessa, Constantina and Daras in quick succession. Around this time, the Romans attacked Lazica forcing Khusro to divert his attention. Khusro immediately attacked Petra and conquered it after killing its commander Johannes.

Meanwhile, a contingent of Romans under Belisarius reached Mesapotamia and ravaged the province. However, the Roman siege of Nisibis failed. Belisarius sent Arethas, an Arab sheikh to invade Persian Mespotamia. But contrary to the general's orders, Arethas ravaged Persian Mesapotamia and took the spoils for himself.

Khusro responded by crossing the Euphrates into Syria in the year 542 and invading Hierapolis. Butn when it appeared as if Hierapolis would fall, Belisarius arrived with his large army and spread his troops along the Euphrates. Khusro fell upon the city of Callinicus and finding it undefended razed it to the ground. However an outburst of plague forced Khusro to retreat across the Euphrates. Khusro, then, invaded Armenia but the prevalence of a plague epidemic forced him to withdraw. The Romans responded by invading the village of Anglon in Persarmenia but the Persians offered a stout resistance forcing the former to withdraw.

In 544, Khusro once again crossed into Mesapotamia and besieged Edessa but was repulsed. Soon peace was concluded for a five-year long period.

Khusro's Second War with Rome
In 549, Rome incited Lazica to revolt against the Persians and sent an army of eight thousand men to aid them. This triggered the Second Roman War of Khusro Anushirvan. The Lazi king welcomed the Romans with open arms to deliver them from Persian rule. Khusro hatched a plot to assassinate the Lazi king but the plot failed.

The hostilies commenced when the Romans besieged Petra. The siege lasted many days but in the end, was successful.

In 550, the Persians took the field under a new general Chorianes and beat back the Lazi. But the retreating Lazi were reinforced by the Romans. They counter-attacked the Persians and killed their commander Chorianes. Soon afterwards, Dagisthseus was replaced by Bessas as the commander of the Roman army. The Romans besieged Petra and after overcoming some stiff resistance offered by the Persians succeeded in conquering the city.

With the arrival of spring, Mermeroes took command of the Persian army and led a large contingent of horsemen and eight elephants into Lazica. The Persians succeeding in conquering most of Lazica. Mermeroes even extended Persian rule over a few neighbouring provinces.

Meanwhile, even while the war was being fought in Lazica, peace was concluded between Rome and Persia by the Roman Emperor Justinian and the Sassanid Khusro Anushirvan. In 553, Mermeroes drove back the Romans and completelky surrounded them within a small tract by the Caspian known as 'The Island' before commencing his return march. But during his return, Mermeroes was affaected by fatigue and passed away at Kutais.

At this juncture, Gubarzes, the king of Lazica quarreled with the Romans and shifted allegiance to Persia. He was eventally killed by the Romans and replaced with a monarch with pro-Rome sympathies. The Rome-Lazi alliance was renewed in 555 and hostilities commenced once more. Nachoragan who replaced Mermeroes besieged the Roman soldiers left behind in "The Island" but was unsuccessful. Nachoragan was eventually recalled to Persia. The war came to an end in 557 by the signing of a peace treaty.

Invasion of Yemen
Abraha, the Abyssinian King of Yemen had died and there was a civil war raging between the heir-apparent Yaksoum who had ascended the throne and his half-brother Saif who was hurt by Yaksoum who had insulted him gravely. Saif sought Khusro's help which was at once accepted. A large Persian fleet under Saif landed at Aden and fought Yaksoum forcing him to flee. Saif ascended the throne and ruled for a couple of years before he was murdered. On his death, Khusro took over the administration of Yemen and made it a Persian province.

War with the Turks
Desirous of an alliance with Persia, Dizabul the Khan of the Turks sent ambassadors with costly presents to the court of Khusro Anushirvan. But Khusro poisoned the envoys and ordered the presents to be thrown into the sea. Humilated, Dizabul invaded Persia from the north in alliance with the Romans. The Turks took Shash, Ferghana, Samarkand, Bokhara and the northern provinces of Iran but fled when Khusro's son Ormazd arrived at the head of a large army. In 571, the Turksa sent envoys to nthe ROman Emperor and the very next year, a large Roman army invaded Persia.

The Last Roman War of Khusro Anushirvan
A large Roman army under Marcian had besieged Nisibis. Khusro at once proceeded to the relief of Nisibis and defeated the invaders. The Romans retreated to the fortress of Daras which was besieged by the Persians. At the same time, the Persian general Adarman crossed the Euphrates with an army of 6000 and ravaged Syria taking all the cities and important fortresses with the exception of Antioch.

Khusro besieged Daras with an army of 40,000 horse and 100,000 foot but the Roman garrison at Daras gave a brave resistance.

Meanwhile, the aged Emperor Justinian abdicated in favor a younger monarch, the Count TIberius who sent envoys to the court of Khusro. Both sides agreed for peace for a period of two years.

But despite the peace, hostilities continued in Armenia. Khusro invaded Armenia with a large army and conquered most of the province. The war was even carried into neighbouring Cappadocia. The Roman general Justinian retaliated by invading Persarmenia anmd pillaging it as far as the Caspian Sea. In 576, the Romans gained the upper hand in Northern Armenia and Iberia while Khusro made an unsuccessful siege of Theodosiopolis. Later that year, the Persian general Tamchosro inflicted a crashing defeat on the Romans under Justinian.

In 578, the Persians invaded Roman Armenia with an army of 20,000 horse. Simultaneously, Tamchosro invaded Amida. The Roman general Maurice responded by invading Persian Armenia and ravaging the country. He plundered the district of Arzanne and crossed into Eastern MEsapotamia and taking Singara, spread death and devastation all over the district. Around this time, Khusro passed away and was succeeded by his son Ormazd.

Reforms of Khusro Anushirvan
F. Altheim has studied the tax reforms of Chosroes in detail. From his conclusions we learn that all land were surveyed and taxed in the same way everywhere, while revenues which formerly frequently went to the nobles were to come into the central government treasury.

Khusro introduced a new class of knights called "dehkans" who were required to maintain armies of their own. These knights were more powerful than feudal lords and villages were entrusted to them for the maintenance of these armies. The whole empire was divided into four military districts each under the protection of a spahbod or Commander-in-chief.

Khusro Anushirvan's time is also renowned for the progress in art and architecture. Qala-e-Dukhtar is a fine example of architecture of Anushirvan. Large quantity of silverware from the time of Khusro Anushirvan have survived to the modern day. There is also a marked improvement in the quality of coins minted by the state indicating progress and prosperity. Excavations in Iran and other parts of the Sassanid Empire have revealed a number of seals from the Anushirvan era.

Throughout the Sassanid era, the Mobeds reigned supreme and even officiated as judges, witnesses and custodians of territorial records.

Legacy
Khusro Anushirvan was arguably the greatest of the Sassanian monarchs. The evolution of classical Iranian civilization reached its culmination during this period. During his reign, pre-conquest Iranian culture reached the pinnacle of greatness and glory inspiring fables and legends. One sch fable is the story of the Arabian Nights which is supposedly a series of tales written during the time of Khusro Anushirvan. During the Arab conquest, the tales made their way to Iraq where they were borrowed by the Arabs and adapted by them to suit local conditions during the time of the Abbasids. During this period, the Persians also translated many notable foreign works into Persian. Burzoe a prominent physician in the Sassanian court and vazir to Khusro Anushirvan translated the Panchatantra into Pahlavi. The Pahlavi translation Khalileh o Demneh was later translated into Arabic and became one of the most popular works of Arabic literature. The Academy of Gundeshapur became renowned all over the world as a centre of learning. The "Pandnamak-i Vozurg-Mihr-i Bukhtakan" (Modern Persian: Pandnameh e Bozorgmehr e Bakhtegan), a book of advice, which is another book attributed to Bozorgmehr, was preserved in the royal treasury (ganj-e shahigan) of Iran in the Sassanid Empire and has been translated into modern languages.

The game of chess reached Europe from India through Persia. It was known to the Indians as chathuranga and to the Persians as shatranj. Brzoe himself is reputed to be a fine chess player.

The renowned Iranoloist Frye regards Khusro Anushirvan as the greatest of the Sassanian monarchs. Muhammad, the Prophet of Islam, is said to have remarked once that he was fortunate to have been born during the reign of an illuminated monarch as Khusro Anushirvan.

Ormazd IV
The Roman Emperor Tiberius sent an offer of peace to Ormazd IV. But the latter rejected the offer. So in 579, the Roman general Maurice set off at the head of a large army and ravaged Kurdistan. He, inititally, planned to penetrate into and occupy Mespotamia. but the treacherous Arab sheikh Alamandarus betrayed him. The Persian general Adarman was sent the head of a large army to fight Maurice but was defeated. Maurice was able to make a safe retreat` to the Roman frontier.

In 581, the Persians crossed the frontier under Tamchosro and invaded Constantia but was defeated and repulsed b y Maurice and Tamchosro himself, slain. At this juncture, Maurice was recalled by the ailing king Tiberius who handed the crown unto him. Maurice sent Johannes to lead the troops in the East. Johannes attacked the Persians but suffered a series of defeates. He was recalled and replacedm with Philippicus. Philippicus spent the years 584 and 585 making deep inroads into Persian territory. The Persians retaliated by attacking Monocartium and Martyropolis. Philippicus responded by invading Eastern Mesapotamia and chased the retreating army all the way to the fortress of Daras. He besieged the fortress of Chlomoron but was forced to withdraw. Philippicus retreated to Amida and handed over the mantle to one Heraclius.

Heraclius led an infantry division into Persian territory and ravaged the plains of the Tigris. However, a mutiny in the Roman army in 588, facilitated the Persian troops who invaded Constantia though unsuccessfully. In 589, the Persians crossed the frontier, and due to the treachery of Sittas a ROman officer, were able to occupy Martyroplois. Philippicus was replaced by Comentiolus under whom the Romans successfully conquered Nisibis. Later that year, Comentiolus successfully penetrated into Persian territory and began to threaten the whole of Mesapotamia. At the very instant when Romans were threatening Martyropolis, the Turks were plundering the northern provinces of the Empire. Ormazd dispatched Bahram with a large army to fight the Turks. The latter defeated the Turks and killed their Khan or leader. When the campaign came to an end, he was sent to lead the Persian troops against the Romans in the West. Bahram ravaged Colchis and other Roman cities but suffered a defeat at Araxes. Ormuzd was jealous of the successes of the Bahram and desired to insult him with the intention of harming his morale. So, he responded to the defeat at Araxes by dispatching a set of women's garments. Enraged, Bahram sent Ormazd a letter of rebuke in which he addressed the former not as the son but the daughter of Khusro Anushirvan. Ormazd dispatched soldiers to arrest Bahram and bring him in chains. But the soldiers sent for the purpose went over to Bahram. Bahram incited his army against Ormazd resulting in widespread rebellion.

At about the same time, Ormazd suspected his son Khusro and his brothers-in-law Bindoes and Bostan of conspiring against him and banished them from the kingdom. Bindoes and Bostan returned from exile in a few months and overthrew Ormazd making Khusro the Emperor of Persia.

Khusro ascended the throne as Khusro II and had to immediately contend with the rebellion of Bahram. Bahram invaded Persia at the head of a large army. Khusro faced him on the banks of the Holwan river but was defeated and fled the kingdom. Bahram captured Ctesiphon and ascended the throne as Bahram VI.

Bahram VI
Soon after Bahram's accession, a rebellion broke out in Armenia. However, Bahram ensured the neutrality of Mesapotamia by strengthening the defences of Anatho and Nisibis.

Meanwhile, Khusro was well received by the Roman Governor of Circesium who not only offered him asylum but also military aid against Bahram.

In early spring of 590, Khusro proceeded at the head of 70,000 Roman troops upto the banks of the Tigris, from where he sent a detachment eastward while he, himself marched alongside the river Zab and in four days, reached the vicinity of Ctesiphon. In a series of two battles, Bahram was defeated and overthrown. He fled to the protection of the Turks of the north leaving Khusro in effective control of all Persia.

Khusro II (Perviz) 591-628
Khusro ascended the throne in 591 when Bahram fled the kingdom. He ruled for 37 years. His period was one of exhilarating highs and humiliating lows. During his reign, the Sassanid Empire reached its greatest extent ever before plunging to depths of ignominy and subordination. He launched a relentless campaign against the Romans in Mesapotamia, West Asia, Turkey, Armenia and Egypt which imposed a great strain on the resources of the country that a decade from the end of Khusro's rule, the Sassanid Empire had passed into history.

As soon as he ascended the throne, Khusro reportedly had his uncles who were responsible for the murder of Ormazd executed. This helped appease the people who had accused him of the guilt of parricide.

During the first eleven years of his reign, the relations with Rome were cordial and there was no animosity of discord which existed between them. In 602, however, the Roman Emperor Maurice who was on friendly terms with Persia, was murdered by Phocus who usurped the throne.

Conquests
In 603, Khusro declared war against the Romans and sent Narses across the frontier while he positioned himself in Mesapotamia. In 605, Khusro besieged Daras at the head of a large army and captured it successfully. Khusro ravaged Mesapotamia and easily conquered the fortress of Amida. In 607, the Persians took Harra, Resaina and Edessa. That very same year, Persian legions crossed the Euphrates and annexed the whole of Syria to the Sassanid Empire. A second Persian army entered Armenia and after successfully taking the strongholds of Satala and Theodosiopolis, invaded Cappadocia and successfully conquered Caesarea Mazaca. Phrygia and Galatia were invested as Persian troops proceeded as far as Chalcedon, opposite to Constantinople.

In 610, the usurper Phocas was deposed and replaced with Heraclius as the Emperor of Constantinople. The country was in turmoil. Taking advantage of this confusion, Khusro sent his general Shahr Barz to invade Syria. Shahr Barz successfully conquered Damascus and made it his base. From Damascus, he launched attacks on Palestine in 614 and conquered it by inciting civil unrest fuelled by a deep hatred for Christian Romans amongst the Jews. Jerusalem fell after a six-day long siege. The Cross of St.Helena, "the True Cross" was discovered and transported to the royal harem of Ctesiphon where it remained in the safe custody of Shirin, the Christian wife of Khsro.

In 616, Shahr Barz entered Egypt after successful conquest of Sinai and the Pelusium. Alexandria fell in a short time and the rest of Egypt was conquered with little resistance. Persian troops advanced to the south and carried the Sassanid arms as far as the Ethiopian frontier. Meanwhile, Shahen commanded the troops in the north. Chalcedon on the opposite shores of the Bosporus to Constantinople was conquered after a short siege and the Persian army could been seen within a mile in sight of the Roman capital of Constantinople.

Heraclius' Invasion of Persia
On Easter 622, the Roman Emperor Heraclius personally took command of the army and attacked the Persians in Armenia in which Shahr Barz was defeated for the first time. The Romans launched a second invasion at the onset of winter taking Lazica in alliance with the Khazars. Then, mustering an army of 120,000 men, Heraclius launched a second invasion of Armenia. Khusro established himself in Azerbaijan and sent two armies one under Shahr Barz and the other under Shahen to face Heraclius. Heraclius, however, withdrew from Armenia and attacked Azerbaijan forcing Khusro to withdraw.

In 624, Khusro took the offensive and dispatched an army to attack Heraclius in Albania. However, Shahr Barz suffered three consecutive defeats, in the last of which his army was cut to pieces.

Early the next spring, Heraclius crossed the Tigris into Arzanne and recovered Martyropolis and Amida. But by the end of March, Khusro had established himself along the banks of the Euphrates forcing Heraclius to withdraw to the safety of Cilicia. The Persians pursued the retreating Romans resulting in a deadly confrontation in Cilicia in which the Persians were defeated. Heraclius wintered at Sebaste(Sivas) in Cappadocia. With support from the Avars, Khusro sent two armies, one under Shahr Barz to assist the Avars in a preplanned siege of Constantinople and the other under Shahen to fight the Romans in Mesopotamia. But Heraclius had secured the assistance of the Khazars against the Persians. He divided his own army in to three and positioned the first in the vicinity of Constantinople while another under his personal command was to effect the conquest of Lazica and a third under Theodore to face Shahen.

Theodore defeated Shahen amidst great slaughter. Heartbroken, Shahen died soon afterwards. The Persians were equally unsuccessful in Constantinople. A confederation of Avars, Slavs and Bulgars besieged Constantinople but were repulsed by the superior artillery of the Romans.

In September 627, Heraclius set out at the head of a large army from Lazica and invaded Mesopotamia. A decisive battle was fought at Nineveh in which the Persians were defeated and forced to retreat. Heraclius invaded Dastaghad on the Euphrates but the turbulent tide of the river blocked his passage further and he returned to Constantinople, completely unmolested and entirely satisfied.

Death
Khusro favored his younger son born to his Christian wife Shirin (Irene) to his eldest son Siroe. Siroe rebelled against his father and arrested him. Khusro was immediately confined to a dungeon and later killed.

Episode of the Letter from Prophet Muhammad
Early Islamic tradition informs us that Muhammad, the prophet of Islam had sent a messenger, Abdullah ibn Hudhafah as-Sahmi together with a letter to preach the religion of Islam. The translation of the contents of the letter are as follows:

In the name of Allah, Most Gracious, Ever Merciful

From Muhammad, Messenger of Allah, to Chosroes, Ruler of Persia. Peace be on him who follows the guidance, believes in Allah and His Messenger and bears witness that there is no one worthy of worship save Allah, the One, without associate, and that Muhammad is His Servant and Messenger. I invite you to the Call of Allah, as I am the Messenger of Allah to the whole of mankind, so that I may warn every living person and so that the truth may become clear and the judgment of God may overtake the infidels. I call upon you to accept Islam and thus make yourself secure. If you turn away, you will bear the sins of your Zoroastrian subjects.

The legend also says that in refusal and outrage, Khosrau tore up Muhammed's letter and conveyed his determination to stick on to Zoroastrianism. In reply, the Prophet is said to have said: "May his kingdom tear apart".

Devout Muslims support the view that it was due to the curse of the Prophet that Khusro was murdered by his own son and the kingdom tore apart. However, the episode of the letter is rejected by a fair number of historians as a "fable" and "part of baseless propaganda".

Character of Khusro Perviz
Khusro II is always presented as a rash and daring monarch who never hesitated to take risks. However, nearly all accounts agree with the point that he lacked common sense. Khusro II is always regarded as a mixture of opposites. Despite his failures at the end of the reign, he was still one of the best monarchs of the Sassanian Empire and certainly the greatest monarch of his time and the most deserving person for the epithet of Eberwiz or Perviz, The Victorious.

Religion and Religious Movements
During the later part of the 5th century, a new faith arose in Iran which posed a serious threat to Zoroastrianism. This was Mazdakism which numbered at least one Sassanian Emperor amongst its followers. However, the new tide ebbed away as quickly as it had arisen. The might of Zoroastrianism and its hold upon the people was visible when Qobad was deposed by the Magi. Since then, Mazdakism rapidly declined though it survived as a minor cult till the 10th century AD. Zoroastrianism made a splendid recovery and continued to hold sway despite the introduction of corrupt practices and un-Zoroastrian elements in the new faith.

Mazdak
Mazdak was born in Persepolis to one Bamdat. Early in his life, he was a Zoroastrian High Priest and later renounced the creed in its existing form and declared himself to be a 'Reformer of Zoroastrianism' and a Champion of the Poor. He preached a kind of Socialism and incorporated these principles into his new faith.

Precepts of Mazdak
According to Mazdak, property and marriage were mere human inventions, contrary to the will of God, which required an equal division of the good things of this world among all, and forbade the appropriation of particular women by individual men. In communities based upon property and marriage, men might lawfully vindicate their natural rights by taking their fair share of the good things wrongfully appropriated by their fellows Adultery, incest, theft, were not really crimes, but necessary steps towards re-establishing the laws of nature in such societies. To these communistic views, which seem to have been the original speculations of his own mind, the Magian reformer added tenets borrowed from the Brahmins or from some other Oriental ascetics, such as the sacredness of animal life, the necessity of abstaining from animal food, other than milk, cheese, or eggs, the propriety of simplicity in apparel, and the need of abstemiousness and devotion.

Rise and Fall of Mazdakism
Mazdakism immediately found favor with the masses. One of the early converts was the Sassanian Emperor Qobad I. Qobad hated the Persian nobility and wished to curb their powers. He, therefore, recognised Mazdakism as the tool with which to tackle them. So, he let loose and orgy of forceful conversions outlawing other faiths and destroying fire temples. These acts provoked the ire of the Magi and Qobad was deposed. He, however, returned in three years and ascended the Sassanian throne. However, he stopped to lend official sanction to the faith. The proselytization of Mazdakism and Mazdakite ideals were curbed. Mazdak himself was killed at a banquet in 528 by the Crwon Prince Khusro Anushirvan.

Legacy
Despite the assassination of Mazdak in 528, the new faith did not fizzle out. On the contrary, it long survived him and even the Islamic invasions. The Khorramdin Movement was inspired by Mazdakism and it has been long believed that its foremost leader Babak Khorramdin was himself a Mazdakite. However, by the 10th century AD and the rise of the Turks, the religion had almost died. Mazdak is universally recognized as the first socialist in history.

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


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Earthquakes

This book will be on earthquakes, a natural disaster that can kill and destroy. But with proper prediction, we can figure out where there is a lot of danger and how to prevent as many casualties as possible. If you are interested in volcanoes, but think that you should learn about seismology as well, then here is the place

Table of Contents

 * /Plate Tectonics/
 * /Basics of Earthquakes/
 * /Measuring and Predicting Earthquakes/
 * /Seismology and the Seismograph/
 * /The Seismologist/
 * /Special Topics/
 * /Some Earthquakes Around the World/

Resources

 * Volcanoes—Volcanoes and earthquakes are often seen together.
 * The US Geological Society (USGS)—The USGS researches earthquakes and volcanoes, among other things.
 * DK E-guide Earth—The DK E-guide to Earth is Internet-linked. Here is the section on earthquakes.
 * Incorporated Research Institutions for Seismology (IRIS)—IRIS is a non-profit consortium dedicated to the acquisition, management, and distribution of seismological data.

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Template:Earthquakes/header

 Earthquakes

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User talk:J Hill~enwikibooks

Request for upload of an image
Hi J Hill. I wonder if you could upload this image to commons so that I can use it on the danish wikibooks. I have started to make the flute book into danish after the english one - more or less. Please contact me here if you do so - I would be very pleased. --CarinaT (talk) 12:54, 3 August 2008 (UTC)

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Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called J Hill. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name J Hill~enwikibooks that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.

Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.

Sorry for the inconvenience.

Yours, Keegan Peterzell Community Liaison, Wikimedia Foundation 23:15, 17 March 2015 (UTC)

Renamed
 This account has been renamed as part of single-user login finalisation. If you own this account you can |log in using your previous username and password for more information. If you do not like this account's new name, you can choose your own using this form after logging in: . -- Keegan (WMF) (talk) 05:03, 19 April 2015 (UTC)

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text: User talk:86.144.194.238

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—  master son T - C

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User talk:Cuvtixo

Hello!

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Chess Strategy/The center

The significance of the center
Many inexperienced chess players will often ignore the center. This is a poor idea. The center is the most important part of the chessboard, as pieces from the center can easily move to either flank with great speed. However, amateurs often prefer to concentrate on the king's side of the board. This is an incorrect mindset, and this page will tell you why.

The five schools
Let's start out with a little history:

The Romantic School
Starting in the mid-1800s, a school of thought called Romanticism began to take hold in the chess world. Romanticism is the philosophy of many players, that the king's flank is the most important. Romantic players often played for tactics alone, ignoring the center. In fact, winning came second to winning with style.

The Classical School
Then came the first World Champion, Wilhelm Steinitz, who crushed his opponents with his deep positional understanding. He was the first modern master to impress upon his students the importance of the center. Some of his later disciples, including Tarrasch, Lasker, and Capablanca, went on to spread his beliefs about the center. Tarrasch was the leader of this school of thought, and was called "the father of Classical dogma".

The Hypermodern School
In the 1920s there was a revolution in chess. Several Central European players like Reti, Nimzowitsch, and Gruenfeld burst onto the chess scene to dominate chess during the next few decades. Their ideas formed the basis for the Hypermodern school. The idea was that a large pawn center would eventually overextend itself and become a target. Nimzowitsch in particular believed in the importance of piece play against the center. His legacy, the Nimzo-Indian Defense, is very popular today with the world's strongest grandmasters. It involves restraining the central pawns with pieces.

Russian Dynamism
During the 1930s Hypermodernism and Classical dogma often clashed with each other. Classical dogma was more popular than Hypermodernism, and eventually two openings threatened to dominate international chess: the Queen's Gambit Declined and the Ruy Lopez, both sound classical openings. In the end, after Alekhine's death, a new generation of Soviet masters took hold, introducing a new philosophy regarding the center.

The Russian Dynamism, a blend of Hypermodernism, which stresses piece play, and Classicalism, which emphasized the pawn center, came with a welcome change to the Indian Defenses and the Sicilian Defense. The idea behind the Russian Dynamism was that it is okay to allow central pawn weaknesses for dynamic piece play. This brought with it a variety of new openings, such as the Boleslavsky Variation in the Sicilian Defense (1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 d6 6.Be2 e5!), which allows a hole on d5 in return for active play against the e4-pawn.

The Modern School
Essentially, the Modern school was introduced by Bobby Fischer. Fischer believed that a dose of all three schools was the correct approach to chess, and had wonderful games using all ideas, including his many great victories with the Najdorf Sicilian. Later world champions like Karpov and Kasparov built up on his work, leading to the present-day school of thought that all previous ideas were correct in their own way.

The pawn center
What Classical masters emphasized was the importance of the pawn center. This is still good today, and will be good for a long time. For example, the game at right, Keres-Fine, Ostend 1937, shows an instructive example of the pawn center.

White has a mighty pawn center, and here is how he brilliantly exploits its power: 21.d5! White sacrifices a pawn to blunt Black's pieces and advance his e-pawn. 21....exd5 22.e5 Nd7 23.Ng5 Nf8 24.Nxh7! White's pawn center allowed him to start a brutal attack and won in seven moves.

Notice how White's central pawn duo was very strong where they stood. Even standing on e4 and d4 the pawns can be very powerful, too. Black's passive formation would have allowed White to keep his pawns where they stood, influencing the course of the game. White could have played the pawn break d4-d5 at any moment in the game, followed by the advance e4-e5 to kick back the Black knight, with further preparation. Also, it is a typical idea to block d5 and then follow with e4-e5. e4-e5 immediately would have allowed Black to sink his knight on d5. However, with the intermezzo d4-d5, Black's pieces were blunted and White immediately seized the initiative.

Play against the pawn center
If your opponent has a massive pawn center, there is often no need to fear if you have significant counterplay. Although a pawn center marks out a spatial advantage, you can try undermining its support. For example, in one game against Letelier at Leipzig 1960, Fischer, as Black, played 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 0-0. This is a Fischer idea, which is simply a move-order tool. 5.e5 Ne8 6.f4 d6 7.Be3 White erroneously believes that his center is invincible. As Fischer will prove, this idea is wrong. 7....c5! Fischer sacrifices a pawn to undermine the center and open lines to White's uncastled king. 8.dxc5 Nc6 9.cxd6 exd6 10.Ne4 Bf5 11.Ng3 Be6 12.Nf3 Qc7 13.Qb1 dxe5 14.f5 e4! Black's pawns have supplanted White's in the center. White is coming under serious attack and cannot hold back the threats to his king, which eventually came through on move 23.

Another example of undermining in the opening occurs in the Alapin Variation of the Sicilian Defense. 1.e4 c5 2.c3 White hopes to build up a strong pawn center. 2....Nf6 3.e5 Nd5 4.d4 cxd4 5.cxd4 e6! Restraining the pawn center and opening up the a3-f8 diagonal for Black's bishop. 6.Nf3 d6! Destroying the beachhead at e5. Black is assured of an even game.

Let's begin with a simple axiom. The purpose of maintaining a pawn center is to squeeze the opponent for space. You will have more space if you can deny the opponent's pieces squares. However, if your center looks nice but does not really gain space (i.e. it gives him squares), then it really doesn't mean anything at all! That was what Black had in mind when he played the following game, which is Scheichel--Adorjan, Hungary 1971. 1.d4 Nf6 2.c4 g6 3.Nc3 d5 The ultra-hypermodern Grünfeld Defense, which gives White a pawn center so that Black can target it. In this game, White plays the super-sharp Exchange Variation. 4.cxd5 Nxd5 5.e4 Nxc3 6.bxc3 Bg7 7.Bc4 O-O 8.Ne2 c5 9.O-O Nc6 10.Be3 Qc7 11.Rc1 Rd8 This position has been played over and over in many Grünfeld games. White is trying his best to uphold the integrity of the center, while Black is trying to destroy it. 12.h3 White would like to play f2-f4, gaining even more space, but after ...Bg4 Black would be able to chop off one of the defenders of d4. 12...b6 13.f4 e6 14.Qe1 Na5 15.Bd3 f5! Hoping for the weakening 16.e5? when 16...c4 17.Bb1 Bb7 would give Black domination over the light squares. 16.g4 Bb7 as seen in the diagram to the left.

White's center is under attack by all of Black's pieces! White should not play 17.exf5 gxf5 18.gxf5 Re8, which would leave Black with more active pieces and leave White with an exposed king and weak pawns. 17.Ng3 Qd7 18.Rd1 cxd4 19.Bb1? An error. White cannot afford this loss of time. 19...Nc4 20.Bxd4 e5! The center is blown to bits and White's uncoordinated pieces are exposed. 21.fxe5 fxg4 22.Qe2 Qc7 23.Qxg4 Nxe5 After the resultant pawn exchanges, we see that all that is left of White's once-mighty pawn center are two weaklings on c3 and e4. Also note that Black's minor pieces are infinitely superior to White's. 24.Qg5 h6 25.Qe3 Rf8 26.Kg2 Ba6 27.Rxf8+ Rxf8 28.Bxe5? Critically weakening the dark squares. Qxe5 29.Bc2 Bc4 30.Bb3 Bxb3 31.axb3 Qxc3 32.Qxc3 Bxc3 33.Rd7 Rf7 and White resigned. He is down some material, and the endgame is hopeless for him.

The pawn center as regards the attack
Going back to the position in Keres—Fine, we notice that the pawn center was one of the things that guaranteed a successful kingside attack. Control of the center is vital to the success of the attack on the flank. An attack on the flank, therefore, is dependent on the attacker's control of the center or the closed center. Either way, this kind of attack is only successful when the defender cannot land a counterpunch in the center. For example, the game at right, Rodriguez—Tringov, Buenos Aires 1978, shows this drastically.

All of Black's kingside pawns are on their initial squares, so it appears that it would be hard for White to attack there. However, this is not the case. Indeed, there is an avalanche of pawns hanging over Black's head! However, this attack is sure to fail for three reasons:

 * 1. White's king is awkwardly placed.
 * 2. Black is not castled on the kingside.
 * 3. Black can counterattack in the center.

Black, noting all three of these conditions, decides that the time is ripe for classic Sicilian counterplay. 18....d5! Black counters a wing attack with play in the center. The sacrifice of the pawn is only temporary, for if 19.exd5, 19....Qc5+ 20.Kg2 Bxd5, with an excellent game for Black due to the open center and his bishop pair. 19.Kg2 dxe4 20.Kh2 e3! Now it is easy to see that White's kingside pawn advance was premature and left the kingside overextended. Black's counterattack in the center stopped the attack before it began. Meanwhile, White is powerless to stop Black's central play. 21.Bg2 Rd8 and White resigned because there is no stopping penetration on the second rank with 22....Rd2.

When the center is stable
However, in the case of a stable center, where the defender cannot hit back in the center, a wing attack is usually a good idea. For example, if a wing attack is started, the defender can't do anything about it in the center. He will have to sit passively and defend, waiting for the attacker to slip. Otherwise, he will usually get mated. Of course, you could riskily play for mate on the king's wing, or you could push for a stable spatial advantage in the center. Both options are good, but it's usually just a matter of taste.

title: Chess Strategy/The center


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Naming/How to name a child/Considerations

The primary considerations people tend to consider in choosing a name include:

 * Impression
 * Sound
 * Group identity
 * Ethnic
 * Traditional or novel
 * Popularity
 * Meaning
 * Associated people
 * Ease

Impression
Discussions of names (baby name books) tend to stress the origins and meanings of names, rather than the impressions generated by names.

In "Baby Name Report Card", Albert Mehrabian measures the impressions name generate by 5 parameters: ...and uses the example of "Chad" as a name producing a very positive impression, while "Bud" produces a very negative impression; both are very masculine.
 * Ethical-Caring
 * Popular-Fun
 * Successful
 * Masculine-Feminine
 * Overall Attractiveness

Note that names can shift gender over time.

Popularity
Popularity is a key aspect of a name; one may distinguish 3 overall categories, namely: very common, very uncommon, and medium popularity. Special considerations apply to names changing in popularity, notably fad names. Unique names are similar in practice to very uncommon names, while foreign names may be more or less popular in different country.

In the US today, a significant number of parents choose names in each such popularity category – the plurality have a medium popularity name, while a significant number have a popular or very uncommon name. In the past (19th century through 1950s), the most popular names were extremely popular (over 20% of children in early 19th century England and Wales had the most popular name – John or Mary, respectively) and very uncommon names (not in top 1,000) were very rare (5% in 1950 US), but very common names have become less popular, while very unusual names have become more popular.

Very common names are easy (to pronounce, remember, or spell), but less distinctive and potentially boring, and often overlap with someone else’s name (hence resulting in nicknames or use of other names); very common names can be common over the long term (a classic, like John or Mary), or can be popular over the short-term (a few years) or medium term (a few decades, like Jennifer from 1960s through 1980s). Very uncommon or unique names are distinctive and interesting (potentially distractingly so), and avoid overlap (they are almost always unique in a given group), but can be difficult to use. Medium popularity names fall between these extremes – they are generally easy (recognizable), if not to the same degree as common names, and reasonably distinctive, though not as unique as very uncommon names.

One issue is medium-term popular names, pejoratively “fad names” – names that increase sharply in popularity to the point of becoming very common, and then decrease sharply in popularity. These result in the name being common in one age group (cohort), but not common over the long term, and becomes associated with a generation. Beyond being very common in one’s cohort, medium-term popular names (like Jennifer) differ from long-term popular names (like Mary) in being more timely, less timeless – thus they can sound more contemporary, but can also sound dated when they are no longer popular. The long-term common names are by their nature stable, and thus a popular name that is not a long-term classic is likely of only medium-term popularity, and thus likely to fall out of popularity in the coming years. Further, once the fad is over – after a once-popular name has dropped out of fashion – people usually avoid it for several decades, as it sounds like a different generation. By contrast, short-term popular names are largely associated with a person, usually a celebrity, but sometimes an event, and tend to last only a few years.

Popularity can be used as a gauge both before or after choosing candidate names: one can choose a candidate name and then check its popularity, to see that it is not too popular or rare – or recently faddish (recent increase in popularity, but not yet very common); or one can look at a range of names in the desired popularity (say, top 10, top 200, top 500–1,000, etc.) and choose among them. One may also look at how the popularity of a candidate name has changed over time – particularly if it is significantly increasing or decreasing in popularity, or was once popular (hence faddish) but no longer so.

Associated people
Naming after a relative or a celebrity (classical or contemporary) is quite common.

Further, some full names are relatively common, such as John Adams, so one may wish to check if there are any historical figures which may come to find for a given full name, to avoid spurious associations or create intended ones, if this is desired.

Ease
Ease to pronounce, read, and spell.


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User talk:76.19.29.52

Join Us!
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title: User talk:76.19.29.52


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Applicable Mathematics/Matrices

Matrices
A matrix is a rectangular array of numbers enclosed in brackets. In a notational sense, what differentiates a list of numbers from a matrix is its format. The numbers are listed so that each number has a certain, specific position between the brackets. Each number, or value, in a matrix is called an entry.

One of the main benefits of matrices is the properties which allow them to be manipulated and used for many different, but useful purposes.

Matrices can vary in size. This variation in size is called dimensions. Just like the dimensions of a room (width x length) matrices have dimensions (number of rows x number of columns). Thus, a 2 x 3 (read 2 by 3) matrix will have 2 rows and 3 columns.

Example of a 2 x 3 matrix:

M = \begin{bmatrix} 572 & 98  & 302\\     1  & 732  & 22\\  \end{bmatrix} $$

Another term associated with matrices is address. Like your home address, an address describes where each value, or entry, of a matrix lives. The address is composed of the lowercase letter of the matrix with the row and column number (in that order) as subscripts.

Using the 2 x 3 matrix M as an example, the positions of the values are as follows:

 * $$ M = \begin{bmatrix} m_{11} & m_{12} & m_{13} \\ m_{21} & m_{22} & m_{23}\end{bmatrix} = \begin{bmatrix} 572 & 98 & 302 & \\ 1 & 732 & 22 \end{bmatrix}$$

A square matrix is any matrix that has the same number of rows as it does columns.

Example: 2 x 2 or 3 x 3 matrices are both square matrices.

 * $$ 2 x 2 = \begin{bmatrix} {\color{red}1} & 12\\ 21 & {\color{red}2} \end{bmatrix}

\qquad 3 x 3 = \begin{bmatrix} {\color{red}7} & 9 & 30 \\ 1 & {\color{red}2} & 2 \\ 5 & 43 & {\color{red}6}\end{bmatrix}$$

Take note of the numbers in red above in the 2 x 2 and 3 x 3 square matrices. These numbers are in the addresses of the main diagonal. The main diagonal of a square matrix is the diagonal from the upper left corner entry to the bottom right corner entry. Notice that only square matrices can have a main diagonal.

Adding and Subtracting Matrices
To add or subtract matrices, the sum or difference is found when addition or subtraction is applied to corresponding entries.

For example,

\begin{bmatrix} {\color{red}7} & {\color{blue}4} \end{bmatrix} +  \begin{bmatrix}{\color{red}3} & {\color{blue}9} \end{bmatrix} = \begin{bmatrix}{\color{red}10}& {\color{blue}13} \end{bmatrix} $$

\begin{bmatrix} {\color{red}a_{11}} & {\color{blue}a_{12}} \end{bmatrix} + \begin{bmatrix}{\color{red}b_{11}} & {\color{blue}b_{12}} \end{bmatrix} = \begin{bmatrix}{\color{red}a_{11}+ b_{11}}& {\color{blue}a_{12}+ b_{12}} \end{bmatrix} $$

\begin{bmatrix} {\color{red}7} & {\color{blue}4} \end{bmatrix} -  \begin{bmatrix}{\color{red}3} & {\color{blue}9} \end{bmatrix} = \begin{bmatrix}{\color{red}4}& {\color{blue}-5} \end{bmatrix} $$

\begin{bmatrix} {\color{red}a_{11}} & {\color{blue}a_{12}} \end{bmatrix} - \begin{bmatrix}{\color{red}b_{11}} & {\color{blue}b_{12}} \end{bmatrix} = \begin{bmatrix}{\color{red}a_{11}- b_{11}}& {\color{blue}a_{12}- b_{12}} \end{bmatrix} $$

Since addition or subtraction takes place using corresponding entries, matrices must have the same dimensions in order to complete either operation.

Consider this operation

\begin{bmatrix} 52\\   36\\  \end{bmatrix} +

\begin{bmatrix} 12 & 16 & 5\\ \end{bmatrix} ====> \begin{bmatrix} a_{11}\\ a_{21}\\ \end{bmatrix} +

\begin{bmatrix} b_{11} & b_{12} & b_{13}\\ \end{bmatrix}\quad {\color{red}CAN'T\quad BE\quad  DONE} $$

\begin{bmatrix} a_{11} + b_{11} & ? + b_{12} & ? + b_{13}\\ a_{21} + ? & ---       & ---\\ \end{bmatrix}$$

Now consider these matrices

\begin{bmatrix} 52 & 4\\   36 & 18\\  \end{bmatrix} +

\begin{bmatrix} 12 & 16\\   34 & 2\\  \end{bmatrix} ====> \begin{bmatrix} a_{11} & a_{12}\\ a_{21} & a_{22}\\ \end{bmatrix} +

\begin{bmatrix} b_{11} & b_{12}\\ b_{21} & b_{22} \end{bmatrix} = \begin{bmatrix} a_{11}+b_{11}& a_{12}+b_{12}\\ a_{21}+b_{21} & a_{22}+b_{22}\\ \end{bmatrix} = \begin{bmatrix} 64 & 20\\   70 & 20\\  \end{bmatrix}

$$

Commutative Property
Matrix addition is commutative $$ A + B = B + A$$

\begin{bmatrix} 5 & 9 & 0\\   1 & 3 & 2\\  \end{bmatrix} + \begin{bmatrix} 7 & 8 & 3\\   4 & 7 & 6\\  \end{bmatrix}= \begin{bmatrix} 7 & 8 & 3\\   4 & 7 & 6\\  \end{bmatrix} + \begin{bmatrix} 5 & 9 & 0\\   1 & 3 & 2\\  \end{bmatrix} $$

>______________ $$ \begin{bmatrix} 12 & 17 & 3\\    5 & 10 & 8\\  \end{bmatrix} = \begin{bmatrix} 12 & 17 & 3\\    5 & 10 & 8\\  \end{bmatrix} $$

Associative Property
Matrix addition is associative. $$A + B + C = (A + B) + C = A + (B + C)$$

$$\begin{bmatrix} 4 & 7\\   1 & 8\\  \end{bmatrix} + \begin{bmatrix} 3 & 18\\   24 & 7 \\  \end{bmatrix} + \begin{bmatrix} 1 & 8\\    14 & 6\\  \end{bmatrix} = \Bigg(\begin{bmatrix}   4 & 7\\    1 & 8\\  \end{bmatrix}+

\begin{bmatrix} 3 & 18\\   24 & 7 \\  \end{bmatrix}\Bigg) +

\begin{bmatrix} 1 & 8\\    14 & 6\\  \end{bmatrix} =

\begin{bmatrix} 4 & 7\\   1 & 8\\  \end{bmatrix}+ \Bigg(\begin{bmatrix}   3 & 18\\    24 & 7 \\  \end{bmatrix} +

\begin{bmatrix} 1 & 8\\    14 & 6\\  \end{bmatrix} \Bigg) $$

$$\begin{bmatrix} 4 & 7\\   1 & 8\\  \end{bmatrix} + \begin{bmatrix} 3 & 18\\   24 & 7 \\  \end{bmatrix} + \begin{bmatrix} 1 & 8\\    14 & 6\\  \end{bmatrix} = \Bigg(\begin{bmatrix}   7  & 25\\    25 & 15\\  \end{bmatrix}\Bigg) +

\begin{bmatrix} 1 & 8\\    14 & 6\\  \end{bmatrix} \qquad \quad=

\begin{bmatrix} 4 & 7\\   1 & 8\\  \end{bmatrix}+ \Bigg(\begin{bmatrix}   4  & 26\\    38 & 13 \\  \end{bmatrix}\Bigg) $$

>_________ $$\begin{bmatrix} 8 & 33\\  39 & 21\\  \end{bmatrix} \qquad \quad \quad = \qquad \qquad \begin{bmatrix} 8 & 33\\  39 & 21\\  \end{bmatrix}  \qquad \qquad \quad =\begin{bmatrix} 8 & 33\\  39 & 21\\  \end{bmatrix}$$

Additive Identity
The zero matrix is the additive identity matrix 'O'.

A Zero matrix is a matrix in which all of the entries are zero. $$ O =\begin{bmatrix} 0 & 0\\   0 & 0\\  \end{bmatrix} $$

Any matrix added to the matrix 'O' will retain its' same values.

Example of additive identity $$A + O = A$$

$$ \begin{bmatrix} 7 & 4 \\   6 & 9 \\  \end{bmatrix} +

\begin{bmatrix} 0 & 0\\   0 & 0\\  \end{bmatrix}

= \begin{bmatrix} 7 & 4 \\   6 & 9 \\  \end{bmatrix} $$

Additive Inverse
It takes two matrices to form a pair of inverses. Two matrices are additive inverses if their sum is the zero matrix. This occurs when the additive inverse of a matrix contains the values opposite of each entry. $$A + (-A) = O$$

$$ \begin{bmatrix} {\color{red}8} & {\color{red}2} & {\color{red}-1}\\ {\color{red}-6} & {\color{red}9} & {\color{red}-3}\\ \end{bmatrix} +

\begin{bmatrix} {\color{blue}-8}& {\color{blue}-2} & {\color{blue}1}\\ {\color{blue}6} & {\color{blue}-9} & {\color{blue}3}\\ \end{bmatrix}

= \begin{bmatrix} {\color{red}8} + {\color{blue}-8} & {\color{red}2} + {\color{blue}-2} & {\color{red}-1} + {\color{blue}1}\\ {\color{red}-6} + {\color{blue}6} & {\color{red}9}+{\color{blue}-9} & {\color{red}-3}+{\color{blue}3}\\ \end{bmatrix}

=

\begin{bmatrix} 0 & 0 & 0\\   0 & 0 & 0\\  \end{bmatrix} $$

Multiplicative Identity Matrix
A multiplicative identity matrix, usually denoted by the letter I, is any square matrix that has a value of 1 in all the entries along the main diagonal and 0 in the remaining entries.

$$ I_{2x2} =\begin{bmatrix} 1 & 0\\   0 & 1\\  \end{bmatrix} \qquad I_{3x3} =\begin{bmatrix} 1 & 0 & 0\\   0 & 1 & 0\\    0 & 0 & 1\\  \end{bmatrix}$$

Any matrix multiplied by an identity matrix will retain it's original entries. $$A x I = A$$

$$ A = \begin{bmatrix} 6 & 15 & 9\\ 23 & 5 & 43\\ \end{bmatrix} \quad \quad I =\begin{bmatrix} 1 & 0 & 0\\ 0 & 1 & 0\\ 0 & 0 & 1\\ \end{bmatrix}$$ $$$$

See Multiplying Matrices

$$ AI= \begin{bmatrix} (6)(1) + (15)(0) + (9)(0) & (6)(0) + (15)(1) + (9)(0) & (6)(0) + (15)(0) + (9)(1)\\ (23)(1) + (5)(0) + (43)(0) & (23)(0) + (5)(1) + (43)(0) & (23)(0) + (5)(0) + (43)(1)\\ \end{bmatrix}$$

$$ AI = \begin{bmatrix} 6 & 15 & 9\\ 23 & 5 & 43\\ \end{bmatrix}$$

Multiplicative Inverse Matrix
If matrices $$ A x  B = I $$ where I is the identity matrix, then A and B are multiplicative inverses of one another.

$$ A = \begin{bmatrix} -1 & 0 & 2\\ 4 & 1 & -1\\ 2 & 0 & 1\\ \end{bmatrix} \quad \quad B = \begin{bmatrix} -0.2 & 0 & 0.4\\ 1.2 & 1 & -1.4\\ 0.4 & 0 & 0.2\\ \end{bmatrix} $$

$$

AB= \begin{bmatrix} (-1)(-0.2) + (0)(1.2) + (2)(0.4) & (-1)(0) + (0)(1) + (2)(0) & (-1)(0.4) + (0)(-1.4) + (2)(0.2)\\ (4)(-0.2) + (1)(1.2) + (-1)(0.4) & (4)(0) + (1)(1) + (-1)(0) & (4)(0.4) + (1)(-1.4) + (-1)(0.2) \\ (2)(-0.2) + (0)(1.2) + (1)(0.4) & (2)(0) + (0)(1) + (1)(0)  & (2)(0.4) + (0)(-1.4) + (1)(0.2) \\ \end{bmatrix}$$ $$ AB = I = \begin{bmatrix} 1 & 0 & 0\\   0 & 1 & 0\\    0 & 0 & 1\\  \end{bmatrix}$$

Thus, matrices A and B are multiplicative inverses of each other.

Multiplying Matrices
Back to Multiplicative Identity Matrix

Another useful property of matrices is called a scalar. A scalar is a number located outside of a single matrix. To apply the scalar to the matrix, simply multiply each entry of the matrix by the scalar.

For example,

{\color{red}3}\begin{bmatrix} 3 & 9 & 15\\   1 & 7.5 & 2\\  \end{bmatrix} = \begin{bmatrix} ({\color{red}3})3 & ({\color{red}3}) 9 & ({\color{red}3})15\\ ({\color{red}3})1 & ({\color{red}3})7.5 &({\color{red}3})2\\ \end{bmatrix} = \begin{bmatrix} 9 & 27 & 45\\   3 & 22.5 & 6\\  \end{bmatrix} $$

In order to multiply two matrices together it is necessary to pay attention to their dimensions. Matrices A and J can be multiplied only if the number of columns in A equals the number of rows in J. Also, another hint is that the product of an a x j and a j x b matrix is an a x b matrix. Notice that the number of columns from the first matrix must equal the number of rows from the second matrix (j = j).

First, we'll look at how to test to see if we can multiply matrices.

Consider matrices Q and R.

$$ Q = 2 \quad x \quad {\color{red}3}\qquad \quad \qquad R = {\color{red}3} \quad x \quad 2\qquad {\color{red}3\ columns} = {\color{red}3\ rows}

$$

Since the number of columns of matrix Q equals the rows of matrix R, these matrices can be multiplied. This will produce a 2 x 2 matrix.

$$ Q = \begin{bmatrix} {\color{red}1} & {\color{red}7} & {\color{red}9}\\ 3 & 5 & 1\\ \end{bmatrix} \qquad x \qquad R = \begin{bmatrix} {\color{red}8} & 9 \\ {\color{red}3} & 5 \\ {\color{red}4} & 6 \\ \end{bmatrix} $$

Multiplying Q and R.

During this process, you may find your fingers and mental addition extremely helpful. You can use your left pointer finger to follow the entries in the rows of matrix Q and your right pointer finger to follow the columns of matrix R. To multiply matrices, add the products of consecutive entries in corresponding rows of matrix Q and columns of matrix R.

$$ QR=\begin{bmatrix} {\color{red}q_{11}} & {\color{red}q_{12}} & {\color{red}q_{13}}\\ {\color{red}q_{21}} & {\color{red}q_{22}} & {\color{red}q_{23}}\\ \end{bmatrix} \begin{bmatrix} {\color{blue}r_{11}} & {\color{blue}r_{12}} & \\ {\color{blue}r_{21}} & {\color{blue}r_{22}} \\ {\color{blue}r_{31}} & {\color{blue}r_{32}} \\ \end{bmatrix}= $$ $$ \begin{bmatrix} QR_{11}={\color{red}q_{11}} \bullet {\color{blue}r_{11}} \quad + &  {\color{red}q_{12}}  \bullet  {\color{blue}r_{21}}  \quad  + &  {\color{red}q_{13}} \bullet  {\color{blue}r_{31}}\quad   QR_{12}={\color{red}q_{11}} \bullet {\color{blue}r_{12}} \quad  + &  {\color{red}q_{12}}  \bullet  {\color{blue}r_{22}}  \quad  + &  {\color{red}q_{13}} \bullet  {\color{blue}r_{32}} \\ QR_{21}={\color{red}q_{21}} \bullet {\color{blue}r_{11}} \quad + &  {\color{red}q_{22}}  \bullet  {\color{blue}r_{21}}  \quad  + &  {\color{red}q_{23}} \bullet  {\color{blue}r_{31}}\quad   QR_{22}={\color{red}q_{21}} \bullet {\color{blue}r_{12}} \quad  + &  {\color{red}q_{22}}  \bullet  {\color{blue}r_{22}}  \quad  + &  {\color{red}q_{23}} \bullet  {\color{blue}r_{32}} \\ \end{bmatrix}

$$

$$ QR = \begin{bmatrix} 1 & 7 & 9\\ 3 & 5 & 1\\ \end{bmatrix}

\begin{bmatrix} 8 & 9 \\ 3 & 5 \\ 4 & 6 \\ \end{bmatrix} = \begin{bmatrix} (1)(8) + (7)(3) + (9)(4) & (1)(9) + (7)(5) + (9)(6)\\ (3)(8) + (5)(3) + (1)(4) & (3)(9) + (5)(5) + (1)(6)\\ \end{bmatrix}

= \begin{bmatrix} 65 & 98 \\ 43 &  58 \\ \end{bmatrix} $$

Determinants
Every square matrix has a value called a determinant, and only square matrices have defined determinants. The determinant of a 2x2 square matrix is the difference of the products of the diagonals.

The determinant of a 2 x 2 matrix can be found as follows:

$$det\begin{bmatrix} {\color{red}9} & {\color{blue}2}\\ {\color{blue}7} & {\color{red}8}\\ \end{bmatrix}= ({\color{red}9})({\color{red}8}) - ({\color{blue}7})({\color{blue}2}) = 58 $$

The " down " diagonal is in red and the " up " diagonal is in blue. The up diagonals are always subtracted from the down diagonals. Matrices that are larger than a 2 x 2 matrix become a little more complicated when finding the determinant but the same rules apply.

 * The " down " diagonal is not necessarily the same as the main diagonal mentioned earlier. The down diagonal happens to be the main diagonal for a 2 x 2 matrix but larger matrices will have multiple down diagonals and only one main diagonal.

Let's find $$det\begin{bmatrix} 1 & 6 & 19\\   8 & 17 & 5\\    14 & 9 & 3\\  \end{bmatrix}$$

When finding the determinant of a 3 x 3 matrix it is helpful to write the first two columns to the right side of the matrix like so,

$$det\begin{bmatrix} 1 & 6 & 19\\   8 & 17 & 5\\    14 & 9 & 3\\  \end{bmatrix} \begin{matrix} 1 & 6 \\ 8 & 17 \\ 14 & 9 \end{matrix} $$

As shown above in the 2x2 matrix, the numbers are color coded. The blue numbers, once again, indicate they are used in the up diagonals, the red are used in the down diagonals, and those in magenta are used in both.

$$det\begin{bmatrix} {\color{red}1} & {\color{red}6} & {\color{magenta}19}\\ 8 & {\color{magenta}17} & {\color{magenta}5}\\ {\color{blue}14} & {\color{blue}9} & {\color{magenta}3}\\ \end{bmatrix} \begin{matrix} {\color{blue}1} & {\color{blue}6} \\ {\color{magenta}8} & 17 \\ {\color{red}14} & {\color{red}9} \end{matrix} = ({\color{red}1} * {\color{red}17} * {\color{red}3}) + ({\color{red}6} * {\color{red}5} * {\color{red}14}) + ({\color{red}19} * {\color{red}8} * {\color{red}9}) - \Big[({\color{blue}14} * {\color{blue}17} * {\color{blue}19}) + ({\color{blue}9} * {\color{blue}5} * {\color{blue}1}) + ({\color{blue}3} * {\color{blue}8} * {\color{blue}6})\Big] $$

$$ = ({\color{red}51} + {\color{red}420} + {\color{red}1,368}) - ({\color{blue}4,522} + {\color{blue}45} + {\color{blue}144}) = -2872 $$

Thus, the determinant of the above 3x3 matrix is -2872.

While square matrices of any size have a determinant, there is no way to extend this diagonal method of computing that determinant for a square matrix of size 4x4 or larger.

Questions
Match the following terms with their definitions.

1. What is a matrix? A mold in which something, such as printing type or a phonograph record, is cast or shaped.

2. How can you change one format of an equation into another? If both funds are in the same fund" family" you can do an "Exchange"

3.How do you perform scalar multiplication? You just take a regular number called a "scalar" and multiply it on every entry in the matrix.

Properties
Match the names of the properties with their equation equivalent.

____Additive Identity >______________ 1. $$A + B + C = (A + B) + C = A + (B + C)$$

____ Additive Inverse >______________ 2. $$A x I = A$$

____ Associative Property >__________ 3. $$ A + B = B + A$$

____ Commutative Property >_________ 4. $$A + O = A$$

____ Multiplicative Identity >__________ 5. $$A + (-A) = O$$

____ Multiplicative Inverse >__________ 6. $$ A x  B = I $$

Properties Solutions

Adding Matrices
Add the matrices.

1) $$ \begin{bmatrix}   52\\    36\\  \end{bmatrix} +

\begin{bmatrix} 12\\    5\\  \end{bmatrix} $$

2) $$ \begin{bmatrix}   12 & 7  & 17\\     6 & 91 & 21\\  \end{bmatrix} +

\begin{bmatrix} 0 & 14 & 32\\   5 & 28 & 1 \\  \end{bmatrix} $$

3) $$ \begin{bmatrix}    3 & 65\\     8 & 32\\  \end{bmatrix} +

\begin{bmatrix} 9 & 71 & 16\\    11 & 4  & 10 \\  \end{bmatrix} $$

4) $$ \begin{bmatrix}     4  & 56 & 14\\     15 & 21 & 35\\  \end{bmatrix} +

\begin{bmatrix} 87 & 13\\    5   & 12\\  \end{bmatrix} $$

5) $$ \begin{bmatrix}    2 & 34 & 41 & 23 & 14\\     5 & 69 & 52 & 6  & 61\\  \end{bmatrix} +

\begin{bmatrix} 1 & 4 & 5  & 17 & 53\\    7  & 8 & 99 & 31 & 93\\  \end{bmatrix} $$

6) $$ \begin{bmatrix}    19\\     32\\     44\\  \end{bmatrix} +

\begin{bmatrix} 12\\    89\\     42\\  \end{bmatrix} $$

Adding Matrices Solutions

Subtracting Matrices
Subtract the matrices.

1) $$ \begin{bmatrix}   52\\    36\\  \end{bmatrix} -

\begin{bmatrix} 12\\    5\\  \end{bmatrix} $$

2) $$ \begin{bmatrix}   1 & 16 & 43\\    6 & 21 & 89\\  \end{bmatrix} -

\begin{bmatrix} 8 & 2 & 61\\    9 & 17 & 26\\  \end{bmatrix} $$

3) $$ \begin{bmatrix}   65  & 14\\    4.5 & 43\\  \end{bmatrix} -

\begin{bmatrix} 31 & 13\\    0 & 24\\  \end{bmatrix} $$

4) $$ \begin{bmatrix}   52 & 17 & 88\\     2 & 63 & 16\\  \end{bmatrix} -

\begin{bmatrix} 13 & 18\\    4 & 11\\  \end{bmatrix} $$

5) $$ \begin{bmatrix}   3.4 & 7.6 \\    5.2 & 9.6\\    1.2 & 8.8  \end{bmatrix} -

\begin{bmatrix} 9.8 & 7.6\\   5.1 & 2.3\\    6.9 & 4.5\\  \end{bmatrix} $$

Subtracting Matrices Solutions

Multiplying Matrices
Multiply the matrices or by the scalar to find the product.

1) $$ \begin{bmatrix}   4 & 7\\    2 & 8\\    3 & 9\\  \end{bmatrix}

\begin{bmatrix} 0 & 6 & 9\\   7 & 2 & 3\\  \end{bmatrix} $$

2) $$ \begin{bmatrix}   4 & 7\\    2 & 8\\    3 & 9\\    1 & 6\\  \end{bmatrix}

\begin{bmatrix} 0 & 6 & 17 & 9\\   7 & 2 & 36 & 12\\  \end{bmatrix} $$

3) $$ \begin{bmatrix}   14 & 0 & 1\\     4 & 2 & 9\\     1 & 6 & 8\\  \end{bmatrix}

\begin{bmatrix} 1 & 4 & 5\\    1  & 2 & 7\\    12 & 6 & 8\\  \end{bmatrix} $$

4) $$ 8 \begin{bmatrix}   41 & 17 & 54\\     2 & 8 & 12\\     4 & 5 &  3\\  \end{bmatrix} $$

5) $$ \begin{bmatrix}   4 & 7\\    2 & 8\\    3 & 9\\  \end{bmatrix}

\begin{bmatrix} 0 & 6\\   7 & 2\\    9 & 3\\  \end{bmatrix} $$

Multiplying Matrices Solutions

Determinants
Find the determinant of the following matrices.

1) $$ \begin{bmatrix}   5 & 1\\    0 & 6\\      \end{bmatrix} $$

2) $$ \begin{bmatrix}   1 & 12 & 4\\    9 &  6 & 3\\    2 &  2 & 0\\  \end{bmatrix} $$

3) $$ \begin{bmatrix}   14 & 4 & 1\\     1 & 2 & 7\\    12 & 6 & 3\\  \end{bmatrix} $$

4) $$ \begin{bmatrix}    1 & 4\\     9 & 3 \\  \end{bmatrix} $$

5) $$ \begin{bmatrix}   7 & 0\\    2 & 6\\  \end{bmatrix} $$

Determinants Solutions

Definitions Solutions
Match the following terms with their definitions.

8 address >_______________ 1. Diagonal from the upper left corner entry to the bottom right corner entry

6 determinant >____________ 2. A rectangular array of numbers enclosed in brackets

3 dimensions >____________ 3. Variation in size of a matrix

1 main diagonal >__________ 4. Any matrix that has the same number of rows as it does columns

2 matrix >________________ 5. Matrix in which all of the entries are zero

7 scalar >________________ 6. The difference of the products of the diagonals

4 square matrix >__________ 7. Number located outside of a single matrix which is multiplied by each entry of the matrix

5 zero matrix >____________ 8. Describes where each value, or entry, of a matrix lives

Properties Solutions
Match the names of the properties with their equation equivalent.

4 Additive Identity >______________ 1. $$A + B + C = (A + B) + C = A + (B + C)$$

5 Additive Inverse >______________ 2. $$A x I = A$$

1 Associative Property >__________ 3. $$ A + B = B + A$$

3 Commutative Property >_________ 4. $$A + O = A$$

2 Multiplicative Identity >__________ 5. $$A + (-A) = O$$

6 Multiplicative Inverse >__________ 6. $$ A x  B = I $$

Adding Matrices Solutions
Add the matrices.

1) $$ \begin{bmatrix}   64\\    41\\  \end{bmatrix} $$

2) $$ \begin{bmatrix}   12 & 21  & 49\\    11 & 119 & 22\\  \end{bmatrix} $$

3)$$\quad$$ Cannot be done because the matrices do not have the same dimensions.

4)$$\quad$$ Cannot be done because the matrices do not have the same dimensions.

5) $$ \begin{bmatrix}    3 & 38 & 46  & 40 & 67\\    12 & 77 & 151 & 37 & 154\\  \end{bmatrix} $$

6) $$ \begin{bmatrix}    31 \\     121\\     86\\  \end{bmatrix} $$

Subtracting Matrices Solutions
Subtract the matrices.

1) $$ \begin{bmatrix}   40\\    31\\  \end{bmatrix} $$

2) $$ \begin{bmatrix}   -7 & 14 & -18\\    -3 &  4 &  63\\  \end{bmatrix} $$

3) $$ \begin{bmatrix}   34  & 1\\    4.5 & 19\\  \end{bmatrix} $$

4) Cannot be done because the matrices do not have the same dimensions.

5) $$ \begin{bmatrix}   -6.4 & 0 \\    0.1  & 7.3\\    -5.7 & 4.3\\  \end{bmatrix} $$

Multiplying Matrices Solutions
Multiply the matrices or by the scalar to find the product.

1) $$ \begin{bmatrix}   49 & 38 & 57\\    56 & 28 & 42\\    63 & 36 & 54\\  \end{bmatrix} $$

2) $$ \begin{bmatrix}   49 & 38 & 320 & 120\\    56 & 28 & 322 & 114\\    63 & 36 & 375 & 135\\    42 & 18 & 233 & 81\\  \end{bmatrix} $$

3) $$ \begin{bmatrix}   26  & 62 & 78\\    114 & 74 & 106\\    103 & 64 & 111\\  \end{bmatrix} $$

4) $$ \begin{bmatrix}   328 & 136 & 432\\     16 &  64 & 96\\     32 &  40 & 24\\  \end{bmatrix} $$

5) Cannot be done because the number of columns from the first matrix does not equal the number of rows in the second matrix.

Determinants Solutions
Find the determinant of the following matrices.

1) 30

2) 90

3) -198

4) -33

5) 42

title: Applicable Mathematics/Matrices


text:
User:Maikel

Le monde aboutira dans un livre. The world will end as a book. Stéphane Mallarmé

title: User:Maikel


text:
Earthquakes/Plate Tectonics

Plate tectonics is the theory (nothing in science can be absolutely proven) that Earth is constantly moving, usually only a few inches per century. If it moves more than this, there is an earthquake. Plate tectonics mainly deals with the crust of the earth, not the mantle or core. The theory of Pangaea is relative to this. The theory of Pangaea theory says that the continents as they are now have moved apart over millions of years to form the world the way it is today, although to be fair to them, some creation scientists/geologists say that Pangaea was pulled apart rather suddenly in geological terms (only 40–150 days!). Plate tectonics is the reason earthquakes in, say, Wisconsin are not as felt or as damaging as an earthquake in, say, California-because Wisconsin is at the center of a plate, and California is at the convulsion of two plates. Plate tectonics is the reason earthquakes happen-when the plates move too fast, an earthquake happens.

title: Earthquakes/Plate Tectonics


text: User talk:76.124.144.221

title: User talk:76.124.144.221


text:
User talk:Mwilgoru.edu

Welcome message
Hello, and welcome to Wikibooks!

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Good luck! --Panic (talk) 00:48, 28 January 2008 (UTC)

Advanced Interactive Media/2008 Project: Weekly Progress Summaries for An Interactive Projective
G'day, I wonder whether you might find Wikiversity to be a more appropriate host for some of this? Wikibooks is a host for textboooks, not coursework, so you might be best served by moving some of the course-specific stuff there before it runs into trouble here. Webaware talk 07:20, 20 April 2008 (UTC)

title: User talk:Mwilgoru.edu


text:
Advanced Interactive Media/2008 Project: Weekly Progress Summaries

Week01: The User and client profiles were discussed with the following notes:

User Description: Issues Raised: - Who is project being designed for?

> Grade school age children 7-9 or 10-12 (one grade-school, homogeneous group)

- Approx number of potential audience?

> 40 per session

- What is the attention span of the target audience?

> 30 seconds to a minute and a half

- Length of media elements?

> 30 seconds to a minute and a half

- What would hold the targeted audience’s attention and effectively get the point across? > Action > Noise > Sound (surround) > Color > Fast paced elements > Interaction > Competition > Keeping the actual audience in motion > The idea of reward

While we are initially planning this with the target audience in mind, we need to not forget who the client ultimately is and what they want. Client is the Kirkpatrick Foundation and the OKC art museum.

Collective Ideas/Suggestions:

- Segmenting the group, and moving the audience

- Competition between the groups

- Competitive scavenger hunt inside the virtual interactive museum (virtual flythrough), per following:

1. Split the group in two and have them compete by interacting with a VR fly-through of the museum (the manipulate where they fly) in looking for treasure 2. Perhaps even better, have another group of their friends actually at the museum, and by     use of two-way A/V communications, they tell the team at the museum where to go and what to look for - Use the Wii-mote to control the virtual artwork inside the VR tent

Project Description: A treasure-hunt competition where the group of children will be split into two teams and each team will use Wii controllers and their half of the enclosure’s projection screens to work their way through a VR environment of the museum, using various collected clues, to find all the objects/information(?) before the other team does. Also in the enclosure would be a chroma-key wall where an actor/college student would show off media interaction by coordinating their movements and behavior with characters projected on through the chroma-key (Interactive team?). Leading up to the enclosure would be a tunnel-like entrance where the students would be introduced to the game and what’s ahead in the enclosure as well images and other aspects of interactive media via flat screens (Design and AV teams) Selling this idea to schools will require printed material (Design team) Other considerations:

- What is the operational budget?

> Potentially $0- $200,000

- What is the timeframe?

> This project is due a year from now.

=
==================================================================================== Week02:

Discussion regarding the look and feel of the final product, geared towards the user-profile from last week: General Considerations:

- Team Leaders: What are you going to do with the selected software to appeal to and reach children (what look and feel for the media)? Preparer a final statement for each team to encapsulate this and post it on Facebook in the respective team blogs

- Project concept is now entitled Surround Screen Video or SSV

- Create a detailed list of everything each team needs from the other teams

- Post what each team will offer on the Facebook, group wall

- Interactive Team Considerations:

- Further discussion given to the overall concept. A third possibility has now made it to the fore, and that is to break up the main group into much smaller groups, as follows:

> The media intro that the children see before entering the SSV is now conducted live by a college student or actor in front of the chroma key wall. On entering, the children see the actor and realise it was a live performance.

> Initially, all the screen inside the SSV are used to give a brief, guided tour of the VR museum interface, conducted by the same student/actor

> Once broken up into their separate groups, each with a Wii controller infront of an individual screen, the presenter shows how the basic interface works – basically click on a 2D layout of museum, and the room clicked grows into a 3D, VR model. Each group at each screen will play games that last no more than ten minutes (approx) where they have to figure out basic puzzles that are based on the art museum room that they are in. Overall, competition could still apply at the as to which team solved the most puzzles.

- Printout concept for high-school brochure: To avoid the usual trifold, create something that folds out rather like the SSV would; i.e. from the centre out to create a circular brochure? For more details, see: http://supercoenbros.blogspot.com/

- Video & Design Teams:

> What sort of transitions should be used in the VR tour when going between rooms? Do we want to have something elaborate that switches between VR and real video, or something more simple and quick that allows the students to quickly go between rooms? We do want some sort of transition so there isn’t just a jarring jump that breaks the illusion.

> This needs to be placed along side the idea of having an actual live team actually in the museum, if we still want to pursue that variation(?)

- Design team Considerations:

> Select colour palette (graphics used will ultimately dictate this)

> Research other ideas on the web – other fads. Particularly look at the Hannah Montana site and the game they have there that John mentioned.

> Remember that we will ultimately be selling the idea and its look to the Kirkpatrick foundation and the museum

> Work on starting the collection of a large library of still images – remember the discussion regarding needing only 1 second exposure duration before moving to the next image.


text:
User talk:Harrychenca

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally. Webaware talk 01:44, 28 January 2008 (UTC)

title: User talk:Harrychenca


text:
User talk:67.183.89.73

Thank you
Hi! Thank you for the help you provided on the Hebrew book. Please keep in mind that there are various transliterations of the Hebrew that are valid. If you want to try to make them more consistent, that's fine, but here are multiple legitimate ways to write some things. Hope you stop back by to contribute more! --CocoaZen (talk) 03:09, 28 January 2008 (UTC)

title: User talk:67.183.89.73


text:
User talk:87.194.203.205

Join Us!
--Whiteknight (Page) (Talk) 05:11, 28 January 2008 (UTC)

title: User talk:87.194.203.205


text:
Talk:Engineering Thermodynamics

About

 * Size: 11,300 words (Apr 2009)

Various
Someone needs to better describe potential energy to include things like energy stored in a spring or chemical bonds.

Someone needs to make this a lot longer. This doesn't describe a small host of necessary things -- phase diagrams, energy types, entropy, enthalpy, mass / heat / energy transfer, steady state, equilibrium, engines (ie Carnot engines), basics of refrigeration, ...

title: Talk:Engineering Thermodynamics


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Talk:Vibrations of Structures

With regard to any suggestion that "vibration of structures" be merged into "vibration" - I comment that this is perhaps not wise. To begin with, "Sound" is also vibration but is worthy of its own explanation. Structural Vibration could be merged with Structural Engineering. It could also be merged with Mechanical Engineering. It is a field of study overlapping both these professions. I have no doubt that Vibration of Structures is a field of engineering, whereas "vibration" could also be seen as a field within the science of physics. My recommendation would be to leave Vibration of Structures on a page of its own, but add a link to it from both the Mechanical and Structural Engineering pages. It has potential for quite detailed explanations and in my opinion warrants being kept separate to avoid confusion. If it had to be merged somewhere - I'd say the most logical place is in with Mechanical Engineering.

The title of the page should be Vibration of Structures, rather than Vibrations of Structures (i.e. drop the (s)). A structure that is vibrating is in a state of vibration. My understanding is that the plural of vibration would be vibration. The word vibration means a repeated movement or displacement. The singular of vibration is a pulse or impulse. Mailliwyrrahwollac (talk) 08:31, 28 January 2008 (UTC)

title: Talk:Vibrations of Structures


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User talk:165.21.154.17

Thanks for spotting that unbalanced equation! Ewen (talk) 08:42, 28 January 2008 (UTC)

title: User talk:165.21.154.17


text: User talk:Mhdmokhtar

title: User talk:Mhdmokhtar


text: User talk:122.164.143.151

title: User talk:122.164.143.151


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User talk:212.248.233.1

Warning comment
Hi - someone using your IP created three nonsense pages in January (deleted). That is why there was a warning. It will always be a problem with shared IPs so you would be better registering a user name. Thanks -- Herby talk thyme 16:50, 22 February 2008 (UTC)

title: User talk:212.248.233.1


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User talk:212.219.235.211

You have been warned
-- Cometstyles 12:21, 19 January 2009 (UTC)

title: User talk:212.219.235.211


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User talk:Bbsteve

Welcome!
Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally.--Laleena (talk) 13:14, 28 January 2008 (UTC)

title: User talk:Bbsteve


text: User talk:80.249.49.5

title: User talk:80.249.49.5


text: User talk:24.228.9.116

title: User talk:24.228.9.116


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User talk:Rkitterman~enwikibooks

Your account will be renamed
Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called Rkitterman. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Rkitterman~enwikibooks that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.

Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.

Sorry for the inconvenience.

Yours, Keegan Peterzell Community Liaison, Wikimedia Foundation 23:38, 17 March 2015 (UTC)

Renamed
 This account has been renamed as part of single-user login finalisation. If you own this account you can |log in using your previous username and password for more information. If you do not like this account's new name, you can choose your own using this form after logging in: . -- Keegan (WMF) (talk) 05:25, 19 April 2015 (UTC)

title: User talk:Rkitterman~enwikibooks


text: User talk:212.194.122.119

title: User talk:212.194.122.119