Albert Einstein was 23 years old and educated in mathematics and physics when he gained employment at the Swiss Patent Office in Bern, Switzerland, in 1902. Einstein’s new job proved undemanding, and he spent his ample free time conducting scientific studies. Without the benefit of a scientific library or theory-minded colleagues, Einstein proceeded to overturn two centuries of scientific thought.

In 1905, the heretofore unknown Einstein presented some of the most influential theories in the history of physical science. Among these was the special theory of relativity, which posited that space and time, previously thought to be absolutes, were relative to the observer. Einstein introduced his famous equation E=mc², the most important product of relativistic physics, in a study also published that year. The equation theorized that an object contained an amount of energy (“E”) equal to the mass of the object (“m”) multiplied by the square of the speed of light (“c”).

By recognizing that mass could be transformed into an enormous amount of energy, Einstein paved the way for the development of nuclear energy. In 1939, the German-born Einstein (then teaching at Princeton’s Institute for Advanced Study) informed President Franklin D. Roosevelt of the potential for building an atomic bomb, cautioning that Germany’s Nazi government already may have one under development. The United States produced an atomic bomb in 1945.

PostScript: Einstein, who urged that only a system of world government could maintain peace in an atomic age, was offered the presidency of Israel in 1952. He chose to remain in Princeton, where he died three years later.

Though the pitch of a train whistle is constant, the whistle seems higher when the train steams toward the station and lower when it steams away. A 38-year-old Austrian physicist named Christian Doppler explained this phenomenon, now known as the Doppler Effect, in 1842.

According to Doppler, the sound waves in front of an approaching source bunch closer together than those in front of a stationary source, thus causing the listener to receive a larger number of waves (and a higher pitch). The waves in front of a source that is moving away spread further apart, which causes the listener to receive a smaller number of waves (and a lower pitch). The theory also applies to light, radio and water waves.

In its greatest application, the Doppler Effect has enabled scientists to determine the motion and velocity of a star by studying the light that the star emits; the light is closer toward the red end of the spectrum (lower frequency) if the star is moving away from Earth, and closer toward the violet end (higher frequency) if it is moving toward Earth. The American astronomer Edwin Hubble thereby discovered in 1929 that galaxies are moving away from Earth at speeds that increase with their distance from Earth, giving rise to the popular theory that the universe is expanding.

PostScript: Closer to home, the Doppler Effect has been used to determine the speed of passing cars, the location of airplanes and missiles, and the rhythms of the human heart.

Odin, the chief god in Norse mythology, knew that he would need powerful forces for the Ragnarok, the doomsday on which the gods would fight evil giants in the world’s final battle. He therefore sent his maidens to battlefields to choose from the fallen warriors. The maidens, known as Valkyries (the “choosers of the slain”), brought the courageous souls to the glorious palace Valhalla (the “hall of the slain”). There, the dead heroes lived in anticipation of the Ragnarok, when they would fight by Odin’s side.

Valhalla teemed with splendor. Its walls were made of gold and its roof comprised of battle shields. The spears that held up its ceiling gleamed so brightly that they were the sole source of light. It was a grand hall, with 540 doors, wide enough to allow 800 fighters to enter abreast, and long tables at which the heroes feasted on boar and mead. Each morning, the slain warriors engaged in violent skirmishes, but their wounds were healed by the time they returned to the banquet.

Two classic Icelandic works inform modern knowledge of Norse mythology. The poet and historian Snorri Sturluson wrote the Prose Edda, or Younger Edda, in the 1220s. Though the anonymous Poetic Edda is a later manuscript, it contains older materials and therefore is known as the Elder Edda.

PostScript: The Anglo-Saxons referred to Odin as Woden, and the word “Wednesday” originates from “Woden’s day.” Additionally, “Thursday” derives from the name of one of Odin’s sons (Thor), and “Friday” from the name of his wife (Frigg).

The legend of a creature with the body and tail of a lion and the head of a man originated in ancient Egypt and spread to western Asia and the Mediterranean world. Greeks who had seen stone statues of the monster during visits to Egypt (where it was most famously depicted by a colossal sculpture at Giza) gave it the name “sphinx.” Around 1600 B.C., the sphinx became an important part of Greek lore, where its appearance departed from the Egyptian model, ultimately assuming a female head, a serpent’s tail, and curved wings.

In Greek mythology, the sphinx was sent from the gods to pose a tantalizing riddle. Perched on a high rock near the city of Thebes, the sphinx terrorized passers-by by demanding that they answer the following question: What is it that walks on four feet in the morning, on two feet at noon, and on three feet in the evening? The sphinx devoured each person who failed to answer the question correctly.

The Greek hero Oedipus finally solved the riddle of the sphinx. The answer was “man,” who crawls on all fours in childhood, walks on two feet in adulthood, and uses a cane in old age. Furious, the sphinx leapt from the rock to her death. Oedipus, meanwhile, was hailed as the liberator of Thebes and made its king.

PostScript: By the fifth century B.C., illustrations of Oedipus’ encounter with the sphinx appeared in Greek art. Some of the depictions suggested that the contest between Oedipus and the sphinx involved physical combat; Greek literature speaks only of the mental challenge.

From the eighth to the fifteenth centuries, an advanced civilization inhabited what now is south-central Arizona. The ancient community mysteriously disappeared, likely the casualty of a severe drought. Pioneers who settled in the area in 1867 realized that they were building on the remains of this former civilization, and therefore named their growing settlement after a mythological bird that similarly had risen from ruin. The bird was known as the “phoenix.”

According to the legend, which dates from the fifth century B.C., the phoenix was unique – only one existed at any one time – and immortal. The bird had brilliant gold and reddish-purple feathers, was the size of an eagle, and lived for 500 years. As the end of its life cycle neared, the phoenix built a nest of fragrant twigs, flapped its wings to set the nest afire, and then was consumed in the flames. A new phoenix, full of youthful beauty, rose from the ashes and started its life anew.

The phoenix was sacred in ancient Egypt, where it was the hieroglyph for the sun, which also seemed to perish in its flames (in the evening) only to rise again (in the morning). Later, the phoenix, with its death and stunning rebirth, appeared prominently in Christian lore as a symbol of resurrection and spiritual renewal.

PostScript: Phoenix, Arizona, is not the only major city to associate itself with the fabled bird. The phoenix’s immortal nature appealed to Rome, the “Eternal City,” and the Roman Empire placed the storied bird on its coinage.

How did King Arthur, the medieval ruler of British legend, acquire his magical sword Excalibur and its priceless sheath that protected its bearer from injury? Two versions exist.

In one account, described in the Alfred Lord Tennyson poem Idylls of the King, Arthur rowed to the middle of a magic lake to receive the jeweled sword from the mysterious Lady of the Lake; dressed in white, she wished to protect him from his enemies and help him “beat his foemen down.” According to this version, as Arthur lay dying after his final battle, he ordered his faithful knight, Sir Bedivere, to throw Excalibur into the lake. After Bedivere complied, an arm, dressed in white, rose to catch the sword “and brandish’d him three times, and drew him under in the mere.”

The other account, popularized by the Disney film The Sword in the Stone, suggests that the sword had been firmly embedded in a miraculous stone, to be removed only by the future king. After every man who tried had failed to extract Excalibur, Arthur, though still a boy, pulled the sword out from the stone and proved himself the rightful heir to the throne.

Sir Thomas Malory’s fifteenth-century work Le Morte Darthur contains both versions. According to Malory, the name “Excalibur” means “cut-steel.”

PostScript: Although the existence of a real-life Arthur cannot be proven, historians cite evidence supporting a belief that he indeed probably lived in the sixth century. In life, Arthur was not a king, but a British warrior who battled invading Germans.

In the seventh century B.C., Egyptian priests told the Greek statesman Solon the story of Atlantis, a utopian island community that had fallen into the Atlantic Ocean more than 9,000 years before. Around 355 B.C., the Greek philosopher Plato made the first written mention of Atlantis, basing his account on the priests’ tale. Plato’s account sparked centuries of speculation as to whether Atlantis had existed and, if so, where.

In his dialogues the Timaeus and the Critias, Plato wrote that Atlantis was larger than Asia Minor and Africa and described its civilization as wealthy and productive. Advanced in engineering and architecture, the society was governed by an ideal political system. Its once-peaceful people, however, became greedy and set out to dominate the Mediterranean world, conquering many lands before finally falling to rival Athens. As punishment from the gods, Atlantis was ravaged with earthquakes and floods, causing the island to sink in a single day and night.

Many scholars believe that the legend may derive from an actual disaster that befell the island of Thera in the Aegean Sea. Around 1500 B.C., an enormous volcanic eruption destroyed most of Thera and set off earthquakes and tsunamis that in turn struck the larger island of Crete, devastating Minoan civilization on both islands. Expeditions to find Atlantis, however, have proved unsuccessful.

PostScript: The legend of Atlantis has aroused popular fascination, generating many spectacular theories. One posits that the Garden of Eden was located in Atlantis. Another suggests that American Indians migrated to the New World by way of the lost continent.

The struggle for woman suffrage (the right to vote) in the United States first gained public recognition in 1848, when Elizabeth Cady Stanton and Lucretia Mott led a women’s rights convention in Seneca Falls, New York. Over the next seven decades, the suffragette movement twice would peak in the aftermath of a defining historical event.

The movement first peaked following the Civil War. The suffragettes had suspended their cause during the war on the assumption that they would gain the right to vote together with the emancipated slaves. After the war, however, many politicians feared that their efforts to enfranchise the ex-slaves would fail if attached to the widely unpopular woman suffrage movement. When the 15th Amendment to the United States Constitution enfranchised only black men, Stanton and Susan B. Anthony broke from the more conservative suffragette alliance to voice radical opposition to the Amendment.

After World War I, the movement reached its pinnacle. Women had made invaluable contributions during the war, and much opposition to woman suffrage had dissolved as a result. New suffragette leadership, meanwhile, encouraged active protest. Feminists marched, picketed and chained themselves to the White House fence. By 1918, 15 states included woman suffrage in their own constitutions. Finally, on August 26, 1920, upon the ratification of the 19th Amendment to the U.S. Constitution, American women were guaranteed the right to vote.

PostScript: The suffragettes believed that political equality would empower women to gain other rights. The fight for the vote, however, sapped the movement, and a women’s revolution would not occur until the revival of feminism in the 1960s.

In 1869, Henry Morton Stanley, a 28-year-old correspondent for the New York Herald, was assigned to travel to central Africa and find the famed British physician and missionary David Livingstone. Livingstone, already the first European to cross the African continent and to sight Victoria Falls (which he named after England’s Queen Victoria), had returned to Africa in 1866 to learn more about the slave trade and the source of the Nile River. He had not been heard from since that time.

Stanley’s search ended in November, 1871, when he found the great explorer, feverish and short of supplies, at Ujiji in present-day Tanzania. Greeting him with the famous words, “Dr. Livingstone, I presume?,” Stanley nursed Livingstone back to health and grew keenly interested in his work. After several months, Stanley left to further extol Livingstone’s legend.

Livingstone’s exploration was born out of a belief that spreading Christianity and new forms of commerce to the African interior would end the slave trade. As his obsession with this quest increased, his body continued to weaken; Livingstone died malarious and emaciated in 1873, still searching for the source of the Nile. His heart was buried in African soil, and his body in London’s Westminster Abbey.

PostScript: Livingstone exerted an early influence on Western attitudes toward Africa. Following his death, Stanley returned to Africa to continue his friend’s explorations. Stanley became the first European to trace the Congo River to its mouth and, helping to usher in an era of imperialistic exploration, later opened up the Congo region for King Leopold II of Belgium.

When the nine-year-old daughter of Samuel Parris, a local minister, and several of her friends went into convulsions, the seaport town of Salem in the Massachusetts Bay Colony fell into hysteria. Many of Salem’s citizens had brought from England a belief in witchcraft and quickly accepted the diagnosis that the young girls were bewitched. Three innocent people were arrested in 1692 for practicing witchcraft on the children: Tituba, a slave in the Parris household who had told them superstitious tales; Sarah Good, an impoverished mother; and the bedridden Sarah Osburn. Good was hanged on Gallows Hill.

Thus began the largest witch hunt in American history. By mid-1693, Salem had executed 20 people and imprisoned about 150 others, including local dignitaries, for alleged witch crimes. The panic ended only when Governor Sir William Phips, his own wife accused of witchcraft, freed all people jailed for the crime. The colony legislature made reparation to the heirs of the witch hunt victims nearly twenty years later.

Some historians theorize that Parris instigated the witch hunt to be rid of certain people linked to the merchant class in Salem, who he believed threatened the traditional views held by his congregation of farmers. Modern speculation suggests that the young girls’ convulsions may have been caused by eating rye bread poisoned by ergot, a fungus that infects flour; ergot is the source of LSD.

PostScript: John Hathorne, one of the judges who committed Tituba, Good and Osburn, was an ancestor of Nathaniel Hawthorne, who changed the spelling of his name after completing college.