As England attempted to conquer France during the Hundred Years’ War, a 13-year-old French peasant girl believed that she heard the voices of saints. At the time, England occupied much of the northern part of the country. Reims, the traditional place for the crowning of French kings, lay deep within English territory, preventing the coronation of the dauphin Charles. At this dark hour, the divine voices instructed Joan of Arc to liberate France from English domination.

In 1429, Joan, then 17, traveled to Charles’ court to begin her mission. Charles was persuaded to allow her to lead a small army into Orleans, which had been under siege for seven months; if the English captured it, Charles’ position would be nearly hopeless. The courageous teenager rescued Orleans within five days and became known as the “Maid of Orleans.” Joan then broke through to Reims, winning several battles along the way, and stood beside Charles as he was crowned king. She had renewed the hopes of her war-weary countrymen.

Charles, however, did little to support Joan’s further military actions. When the Burgundians (French supporters of England) captured Joan in 1430, Charles made no effort to save her. The English paid a large sum for her and delivered her to an English-dominated church court. Joan was condemned as a heretic and burned at the stake in Rouen on May 30, 1431. Twenty-five years later, the charges against her were revoked.

PostScript: France’s national heroine was canonized in 1920. The country now recognizes the second Sunday in May as a holiday in her honor.

In the early 1890s, teenager Ehrich Weiss, having struggled as a trapeze artist and vaudeville performer, tried his hand at magic. Appearing as “Harry Houdini” (the name taken from French magician Jean Robert-Houdin), he discovered an uncanny ability to escape from confines ranging from handcuffs to prison cells and developed a “challenge act” in which he freed himself from various predicaments, including devices that spectators brought to his shows. By 1900, Houdini had become an international sensation.

Among Houdini’s most dangerous and widely publicized feats were his escapes from an airtight tank filled with water (the “Water Torture Cell”); a straitjacket that he wore while hanging upside down high above a large crowd; a nailed crate that had been lowered into a river; and a Scotland Yard prison cell.

Houdini was vigilant in exposing performers who tricked or deceived the public. He even debunked Robert-Houdin’s abilities. Most particularly, Houdini in his later years campaigned relentlessly against those who claimed to have supernatural powers, such as the ability to read minds or communicate with the dead. He duplicated their acts and revealed their methods, showing that their effects actually were achieved through chicanery.

PostScript: Taking his test of spiritualism to the extreme, Houdini agreed with his wife that the first to die would communicate a secret message to the other from the afterlife, if that were possible. Houdini died first, on October 31, 1926 (willing his act to his brother and fellow magician, Hardeen). For 10 years, his wife tried to contact him through mediums, but to no avail.

The current Dalai Lama, born Tenzin Gyatso in 1935, is the 14th in a line of Dalai Lamas, the head of the dominant order of Tibetan Buddhists. The Dalai Lama ruled Tibet from the 1600s until 1959, when Gyatso and 100,000 followers fled to India after a failed revolt against Chinese Communists who had occupied Tibet since 1950. After the Dalai Lama’s flight, the Chinese dissolved the Tibetan government.

Tibetan Buddhism teaches that one’s character is the summation of thoughts and deeds from prior incarnations. Accordingly, Buddhist followers believe that the 14 Dalai Lamas are one Dalai Lama reincarnated in 14 bodies, and have developed a complex process for identifying the new incarnation. Candidates are chosen from among those born after the Dalai Lama’s death and are subjected to rigorous tests; for example, they are shown objects, some of which belonged to the Dalai Lama, and asked if they recognize any of the items as their own.

The Dalai Lama won the Nobel Peace Prize in 1989 for his nonviolent efforts to free Tibet from Chinese domination. He is the author of more than 40 books, including The Art of Happiness, which applies Buddhist principles to the problems of daily life. It spent more than 80 weeks on the New York Times bestseller list.

PostScript: Many celebrities have joined the international support of the Dalai Lama’s cause. In 1996, the first annual Tibetan Freedom Concert, held in San Francisco, drew 100,000 attendees. The following year, the Dalai Lama’s struggle was portrayed in the Martin Scorsese film Kundun.

The political and cultural life of Europe collapsed with the fall of the Roman Empire in the fifth century. Three hundred years later, Charlemagne, who became sole king of the Franks in 771, led a cultural revival that forever lifted Western Europe from darkness.

The hallmark of the “Carolingian Renaissance” was its appreciation of spirituality, legislation, and learning. Charlemagne devoutly respected the church and believed that royalty should spread Christianity. He gave his empire legal codes and initiated educational and economic reforms. Charlemagne’s intellectual advancement perhaps was most momentous, as he called on the best minds from many lands to educate his people and encouraged scholarship.

Charlemagne’s reign also was marked by brutal military campaigns designed to expand his empire. For more than 30 years, Charlemagne waged a bitter war against the pagan Saxons, finally forcing their conversion to Christianity; this campaign included the mass execution of 4,500 Saxons on a single day. Although Charlemagne ultimately controlled practically all Christian lands of Western Europe (assuming the title of Holy Roman Emperor in 800), his empire crumbled quickly following his death in 814. The cultural revival sparked by Charlemagne nonetheless had a permanent influence on Europe, effectively ending the decay of the Dark Ages and overshadowing his ruthless military measures.

PostScript: A biography of Charlemagne by Einhard survives from the period. Einhard writes that the conquering hero had a “friendly and cheerful” face, a “thick, short neck and a belly that protruded somewhat,” and “a higher voice than one would have expected of someone of his build.”

Spurred by ambition, William M. Tweed entered politics before he was 30 and quickly ascended through the New York City establishment. He became the most powerful figure in the Society of Tammany (popularly known as Tammany Hall), an influential Democratic party organization, and practically controlled Democratic city politics in the 1860s. “Boss” Tweed soon became notorious for political corruption.

Tweed used his power to gain control of the city treasury for himself and his associates (the “Tweed Ring”) and then raided the public funds. Among his schemes, Tweed arranged for the city to overpay for goods and services bought from his cronies, and obtained kickbacks from such city contracts. Tweed’s largest fraud involved the construction of the New York County courthouse (the “Tweed Courthouse”), which exceeded its budget more than twenty-five times over. Estimates suggest that the Tweed Ring swindles cost New York City as much as $200,000,000.

The New York Times and Thomas Nast, a political cartoonist for Harper’s Weekly, exposed Tweed’s practices to an outraged nation. Samuel Tilden, chairman of the New York State Democratic Committee, then led a reform movement that resulted in Tweed’s arrest and, in 1873, his conviction. After about a year in prison, Tweed was released, but he was rearrested when the state brought civil charges. Tweed escaped and fled to Spain; because of a Nast cartoon, however, he was recognized there and extradited to New York.

PostScript: Tweed died in 1878, a resident of Ludlow Street Jail. Tammany Hall overcame the scandal and largely dominated city politics until the 1930s.

During stormy weather, a faint blue glow may be seen around the tips of elevated, pointed objects. The flame typically appears around the masthead or yardarms of sailing ships. It also has been observed, however, around the corners of skyscrapers, the ends of airplane wings, and the tops of church steeples, trees, towers, and even cow horns. Though a scientific phenomenon, the glow is popularly associated with a third-century Italian bishop.

The bishop Erasmus, whose name was corrupted into “Elmo,” was one of the patron saints of sailors. Those sailors who observed the tip of light on the masts of their ships believed it to be the manifestation of Elmo’s protection over them. The luminous flame accordingly became known as St. Elmo’s Fire.

St. Elmo’s Fire is the result of a steady electrical discharge from sharp, extended structures. Intense storm activity induces the discharge; when there is high voltage in the air beneath storm clouds, the negative charge on those clouds attracts an accumulation of positive charge at surrounding elevated points. (By principle, opposite kinds of electricity attract each other.) The phenomenon, which may be accompanied by a fizzing or crackling noise, is not dangerous, but sometimes is followed by a more troublesome discharge.

PostScript: It is believed that Erasmus was martyred during the persecution of Christians by Diocletian, the Roman emperor. According to legend, Erasmus was disemboweled, leading those who later suffered from intestinal illnesses to invoke his name.

Spanning only about one percent of the world’s surface, the area called the “Ring of Fire” creates more volcanic and seismic activity than anywhere else on Earth. More than half of the world’s active volcanoes lie along the ring, and thousands of earthquakes occur within the region each year.

Nearly 25,000 miles in length, the Ring of Fire winds in the approximate shape of a horseshoe through a series of diverse lands at the rims of the Pacific Ocean. From the majestic Andes Mountains of South America, the ring stretches northward along the Central American and Mexican coasts to California, the American Northwest, and, at its most northerly point, Alaska’s barren Aleutian Islands. Crossing the Russian peninsula, the zone then travels southward through Japan and the tropical Philippines to New Zealand.

Scientists theorize that the location of the volcanoes and the occurrence of earthquakes along the Ring of Fire are caused by the motion of tectonic plates. A patchwork of these solid and bulky plates (about 50 miles thick), each moving at a rate of a few centimeters per year, form Earth’s surface. In a process known as subduction, the edge of one plate sinks below the edge of another plate, causing earthquakes and leading to the formation of a chain of volcanoes along the border of the upper plate.

PostScript: Among the catastrophic events occurring along the Ring of Fire are the biggest earthquake ever recorded (which, with a magnitude of 9.5, occurred in Chile in 1960) and the eruption of Mount St. Helens in Washington in 1980.

The atom long was thought to be the most fundamental building block of all known matter; indeed, its name derives from the Greek word for indivisible (“atomos”). In the 1900s, however, scientists discovered that even smaller particles, known as protons and neutrons, composed the atomic nucleus. These nucleons then were believed to be “elementary” – that is, to have no known smaller parts. But experiments conducted in the 1960s began to suggest that protons and neutrons possessed an internal structure and therefore were “composite,” not elementary, particles.

In 1964, physicists Murray Gell-Mann and George Zweig, working independently at the California Institute of Technology, postulated the existence of subatomic particles even more basic than protons and neutrons. Borrowing an obscure line from the James Joyce novel Finnegan’s Wake (“Three quarks for Muster Mark”), Gell-Mann gave them the whimsical name “quarks.” In the late 1960s, three physicists at the Stanford Linear Accelerator Center demonstrated the existence of quarks; for this work, the Stanford scientists received the 1990 Nobel Prize in physics.

Quarks (pronounced “kworks”) appear to be truly elementary and are considered the ultimate building blocks, constituting more than 99.5% of every atom. Indeed, famed physicist Stephen Hawking believes that the very early universe likely was a “dense soup” of quarks and antiquarks.

PostScript: There are six types or “flavors” of quarks, differentiated by mass and electrical charge. The flavors arbitrarily are named up, down, strange, charmed, bottom, and top. Though the flavors often are given visual representations, quarks themselves are described as “point-like” and have yet to be observed in isolation.

The magnificent light display aurora borealis results from the interaction between the sun’s activity and the Earth’s atmosphere. Though the phenomenon is not completely understood, researchers have discovered that auroral displays are greatest at times of intense sunspot activity, and believe that the aurora forms as follows.

The sun ejects electrically charged particles of matter, which flow from the sun and travel through space in what is known as the “solar wind.” Some of those particles that reach Earth are caught by its magnetic field and are conducted toward Earth’s two magnetic poles. However, some slip into Earth’s upper atmosphere. The particles that enter the upper atmosphere collide with the atoms and molecules of air (nitrogen and oxygen); this collision excites those atoms and molecules, which in turn causes them to produce the visible aurora.

In North America, the Northern Lights most likely are seen in Alaska and Hudson Bay. The aurora may take a number of forms (such as arcs, rays, or curtains), and most commonly appears in green, the color emitted by oxygen atoms. The aurora typically extends from 60 miles to several hundred miles above the earth’s surface; it may spread across the sky from east to west for thousands of miles.

PostScript: Drawing attention as early as the fourth century B.C., the aurora was first studied in America in the early eighteenth century, when Benjamin Franklin included it in his theories about lightning. More modern investigation included, in 1958, the generation of man-made auroras through the explosion of nuclear bombs in the upper atmosphere.

The Hippocratic Corpus, a collection of about 70 anonymous works including the Hippocratic Oath, is believed to constitute the remains of an ancient medical library located on Cos, a Greek island. Although attributed to the great physician Hippocrates, neither the Oath nor any other works in the Corpus can be proved to have been written by him; indeed, they appear to have been written at different times by different people.

Perhaps written as early as the sixth century B.C., the Hippocratic Oath stands to this day as the guiding code of medical ethics. The Oath has two parts. The obligations between students and teachers of medicine are enumerated in the first section, while the second part sets forth the rules for providing medical treatment and constitutes a summary of ethical principles. In 1948, the World Medical Association adopted a modern version of the Oath.

Today, graduating students at nearly every medical school take some form of the Oath, which may include such maxims as maintaining the confidentiality of a patient’s treatment and fulfilling one’s duty to a patient regardless of race, religion or nationality. Some physicians question the relevancy of the Oath to contemporary medical issues, however, and view it solely as a matter of tradition.

PostScript: Hippocrates, a native of Cos who lived between 460 and 377 B.C., is known as the “father of medicine.” He taught that diseases have natural causes and can be cured through study, and Hippocratic medicine based treatment on factual analysis and clinical observation. Prior to Hippocrates, many physicians used magic, superstition and witchcraft to treat illness.