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In 1541, Francisco Pizarro was cut down by assassins in his own palace in Lima, drawing a cross in his blood before he died. This episode traces how an illiterate, illegitimate man from Trujillo, Spain, rose to topple the Inca Empire, and how the contracts and betrayals behind his conquest ultimately led to his death.

We cover his arrest of Vasco Núñez de Balboa, the partnership with Diego de Almagro and Hernando de Luque, the line in the sand on Isla del Gallo, the Capitulation of Toledo, and the ambush of Atahualpa at Cajamarca. We also examine the ransom room, Manco Inca's rebellion, the encomienda system, the civil war among the conquistadors, and the 1977 discovery of his true remains.

• Why the line in the sand was a calculated gamble rather than pure heroism
• How the Capitulation of Toledo sidelined Almagro and planted the seeds of civil war
• How 168 Spaniards captured Atahualpa despite an army of about 50,000
• The Inca tactics of feigned retreats and boulder ambushes during the siege of Cusco
• How the encomienda system turned conquest into long-term wealth extraction

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Ernest Rutherford compared one of his discoveries to firing an artillery shell at tissue paper and watching it bounce back. This episode follows the farmer's son from Brightwater, New Zealand, who won scholarships to Cambridge's Cavendish Laboratory and went on to become the architect of modern atomic theory.

We trace his early radio receiver and the race with Marconi, his work with Frederick Soddy at McGill on radioactive decay and half-life, his challenge to Lord Kelvin's estimate of the Earth's age, the 1909 gold foil experiment, his wartime sonar research, the discovery of the proton, and his leadership of the Cavendish team that split the atom, along with his famous dismissal of atomic energy.

• How he classified alpha, beta, and gamma radiation by their penetrating power
• The coin-flip analogy that explains radioactive half-life
• How radioactive heat undermined Kelvin's calculation of the Earth's age
• Why the gold foil experiment killed the plum pudding model and revealed the nucleus
• How missing mass led to the prediction of the neutron, later found by James Chadwick

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On September 30, 1913, Rudolf Diesel's cabin aboard the steamship SS Dresden was found empty, his bed unslept in, his nightshirt laid out, and his pocket watch propped up beside it. The engineer whose name is on fuel pumps worldwide had vanished into the English Channel, leaving one of the most debated mysteries of the twentieth century.

This episode traces Diesel from his birth in Paris in 1858 and his family's expulsion during the Franco-Prussian War to his studies under Carl von Linde, his obsession with the Carnot cycle, the explosions that nearly killed him, and the compression-ignition engine that transformed industry. We then weigh the evidence behind three competing theories about his disappearance.

• Why steam engines wasted up to 90 percent of the energy in their coal
• How compressing air until it is hot enough ignites fuel without a spark plug
• The engine that ran on peanut oil at the 1900 World Exhibition
• The bag of 20,000 marks, empty bank accounts, and a cross drawn in his diary
• Suicide, assassination, or a British ruse: the theories behind his disappearance

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In 1224, Genghis Khan smeared fat from a fresh kill on the finger of his nine-year-old grandson and told the crowd to heed the boy's wisdom. That boy was Kublai Khan, who grew up between nomadic Mongol traditions and the settled, cosmopolitan world, and went on to found the Yuan dynasty and rule a unified China.

This episode follows Kublai from his mismanaged estate in Hebei and the brain trust of advisors he built, through the Dali campaign, the civil war with his brother Ariq Böke, and the Li Tan revolt. We explore the four-class system, his global court of foreign talent, the jiaochao paper currency, failed invasions of Japan, and his lonely final years.

• How a disastrous tax policy in Hebei taught Kublai to govern settled farmers
• Why he spared the Dali king and recruited him instead of ordering a massacre
• How cutting grain supplies to Karakorum won the Toluid Civil War
• The rise of the jiaochao and the slide into fiat money and inflation
• Why flat-bottomed riverboats doomed the invasions of Japan

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In 1888, Alfred Nobel opened a newspaper to find his own obituary under the headline "The merchant of death is dead." The mistake, made when his brother Ludwig died, gave the explosives magnate a brutal preview of his legacy. This episode explores the paradox of a solitary, depressed industrialist whose fortune came to fund the world's most famous prizes for peace and achievement.

We trace Nobel from his family's bankruptcy and fortune in St. Petersburg through his work with nitroglycerin, the 1864 explosion that killed his brother Emil, and the invention of dynamite, gelignite, and ballistite. We also examine his secret 1895 will, the troubled launch of the prizes, his ties to Bertha von Suttner, and his letters to Sophia Hess.

• How diatomaceous earth tamed nitroglycerin and turned it into dynamite
• Why smokeless powder transformed the battlefield
• The irony of Nobel being prescribed nitroglycerin for his angina
• How a vague phrase in his will led the Academy to overlook Tolstoy and Ibsen
• Why the economics prize was not part of Nobel's original plan

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As Roman soldiers stormed Syracuse, a 75-year-old Archimedes reportedly told one of them not to disturb his circles drawn in the dust, and was killed on the spot. This episode builds a fuller portrait of the mathematician and engineer who lived from about 287 to 212 BC and bridged pure theory with practical invention.

We explore his correspondence with scholars in Alexandria, his work for King Hiero II, the golden wreath problem and the hydrostatic balance, launching the Syracusia with compound pulleys, and the war machines that held off Rome during the Second Punic War. We also discuss the method of exhaustion, The Sand Reckoner, and the rediscovered Archimedes Palimpsest.

• Why the naked Eureka bathtub story may be less plausible than the hydrostatic balance
• How the law of the lever made moving massive weights a matter of mathematics
• The catapults, cranes, and Claw of Archimedes that terrified the Roman fleet
• Why the burning mirror death ray likely never happened
• How The Method revealed he used imagined physics to discover mathematical truths

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Benjamin Franklin ran away from his Boston apprenticeship as a teenager, spent much of his marriage an ocean away from his wife, and once froze a thermometer on a warm day just to see if he could. This episode looks past the face on the hundred-dollar bill to the complex, flawed, and endlessly curious man who reinvented himself again and again over 84 years.

We follow Franklin from the Silence Dogood letters and his flight to Philadelphia to the Junto, the first subscription library, Poor Richard's Almanack, and his early retirement into science and civic projects. We also cover his Stamp Act misstep, his broken relationship with his loyalist son William, his persona in France, and his late turn to abolition.

• How a 15-year-old Franklin used a fake widow's voice to shape public opinion
• The ether evaporation experiment that anticipated the principle of refrigeration
• Why he refused to patent the lightning rod, bifocals, or the Franklin stove
• How playing a rustic philosopher in Paris secured the alliance that saved the revolution
• His shift from slaveholder to president of the Pennsylvania Abolition Society

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In 1781, Spanish authorities tied José Gabriel Condorcanqui to four horses in Cusco's plaza, but the horses failed to tear him apart. Known as Tupac Amaru II, he was a wealthy, Jesuit-educated descendant of the last Inca ruler who owned a fleet of 350 mules and walked between colonial high society and the brutal reality of indigenous exploitation.

This episode examines the mita forced labor system, the Bourbon Reforms, and forced purchasing that pushed him from legal petitions to revolt in 1780. We cover the execution of governor Antonio de Arriaga, his decree abolishing slavery, the strategic role of his wife Micaela Bastidas, the Battle of Sangarara, the failed siege of Cusco, his capture and execution, and his legacy from the Tupamaros to Tupac Shakur.

• How the mita debt trap kept indigenous workers and their children in permanent servitude
• Why he claimed to act on the Spanish king's orders while overthrowing colonial officials
• How his mule network became a rapid communication system to raise an army
• Micaela Bastidas's role as co-commander and her warning to strike Cusco quickly
• How Spain's cultural bans backfired and fueled indigenous nationalism

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In 1869, around 25,000 people gathered in Central Park to celebrate the 100th birthday of Alexander von Humboldt, yet today most Americans don't know his name. This episode explores the Prussian polymath who taught the world to see nature as an interconnected web rather than a machine of isolated parts.

We follow Humboldt from his cold aristocratic upbringing and career as a mine inspector to his five-year expedition through the Americas with Aimé Bonpland, including electric eels, the climb of Chimborazo, the Naturgemälde, and his observations at Lake Valencia. We also examine his meeting with Thomas Jefferson, his Cosmos volumes, his global network of observation stations, why his fame faded, and the debate over his private life.

• How Humboldt's breath completed a galvanic circuit and made a frog's leg jump
• The climb of Mount Chimborazo and the Naturgemälde infographic linking altitude, climate, and plants
• His early description of human-induced climate change at Lake Valencia
• Sharing New Spain's maps and economic data with Jefferson after the Louisiana Purchase
• Why anti-German sentiment and scientific specialization erased his legacy in America

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Before he built the world's first nuclear weapon, J. Robert Oppenheimer was a clumsy, depressed student at Cambridge, rumored to have laced an apple with chemicals and left it on his tutor's desk. This episode follows how a privileged New York prodigy found his footing in theoretical physics at Göttingen and became one of the most influential scientists of the twentieth century.

We cover his Berkeley years, the Born-Oppenheimer approximation, and early predictions of black holes and neutron stars, then General Leslie Groves's surprising choice to put him in charge of Los Alamos. From the Trinity test to his opposition to the hydrogen bomb, the 1954 security hearing, the Chevalier incident, Edward Teller's testimony, and the 2022 decision vacating his clearance revocation.

• Why moving from experimental to theoretical physics transformed his career
• How the Born-Oppenheimer approximation simplified the math of molecules
• Why Groves chose a manager who could synthesize chemistry, metallurgy, and physics
• The Chevalier incident and how a fabricated story doomed him in 1954
• The gap between scientific discovery and control over how power is used