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Around 30 BCE a Chinese text warned Silk Road travelers about the Big Headache Mountains of the Karakoram, and in the late 1500s the Spanish Jesuit José de Acosta, crossing the Pariacaca pass in the Andes, blamed his nausea and blinding headache on air too thin for human needs. This episode explains why: the air stays about 21 percent oxygen at any height, but falling barometric pressure spreads the molecules out, and water vapor in the lungs takes a growing share of the space. It covers why an elite marathoner can struggle while a less fit person acclimatizes, the three altitude bands, and why no one lives permanently above 5,100 meters.

The body fights back with a racing heart, hyperventilation, more EPO and red blood cells, and 2,3-BPG that helps hemoglobin release oxygen. Those same reflexes can turn deadly, as dilated vessels leak fluid into the brain in HACE and constricted vessels in the lungs burst under pressure in HAPE. The episode covers climb high, sleep low, the 300 meter daily sleeping limit, acetazolamide's trick of acidifying the blood, Aymara coca chewing, and the EPAS1 variant Tibetans likely inherited from Denisovans, then turns to Chilean copper miners who commute from sea level to mines such as Collahuasi.

• Acute mountain sickness, which can begin at 2,000 meters within about 10 hours of arrival
• Roughly 20 percent of fast climbers sickened at 2,500 meters and 40 percent at 3,000 meters
• The Gamow bag, a foot pumped chamber that can simulate a descent of 1,500 meters
• How Andean and Tibetan populations evolved opposite solutions to thin air
• Chile's laws requiring screening and reassignment to lower elevation without a cut in pay

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In 1961, at the Stanford University Nursery School, psychologist Albert Bandura tested whether children learn aggression simply by watching. Seventy two children aged roughly three to five and a half were split into groups that saw an adult attack an inflatable Bobo doll, saw an adult play quietly with Tinker toys, or saw no model at all. The aggressive adults punched the doll, sat on it, hit it with a wooden mallet, and shouted scripted lines like sock him and pow. Each child was then frustrated by being shown fine toys and told they were reserved for other children, and observed for 20 minutes through a one way mirror.

The children copied the exact blows and phrases, and those who saw the calm model were less aggressive than the control group. Boys recorded 270 aggressive acts to the girls' 128. In 1963 Bandura showed 96 children a live model, a filmed model, or an adult in a cartoon cat costume, and all three raised aggression, undercutting the idea that violent media was cathartic. In 1965, 66 children saw the model rewarded, punished, or neither, and the punished group held back until offered treats to show what they had seen, revealing the line between learning and performing that became social learning theory.

• Why girls imitated verbal aggression more from a female model and physical aggression more from a male model
• The reward in the 1965 film: candy, soda, and praise as a strong champion
• A 1990 replication finding children familiar with Bobo dolls up to five times less likely to imitate
• Critiques about ecological validity, biology, and brain development in children under eight
• The ethics of frustrating young children without consent or debriefing

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The cold stimulus headache, better known as ice cream headache or brain freeze, starts on the roof of the mouth. This episode explains how freezing food on the richly vascular palate makes blood vessels constrict and then rapidly swell again, a rebound vasodilation that sets off dense pain receptors. The signal travels along the trigeminal nerve, which also serves the forehead, and the brain refers the pain to the wrong place, the same mechanism that sends heart attack pain to the arm. An alternative theory points to the anterior cerebral artery flooding the brain with warm blood, raising pressure inside the rigid skull until the vessel constricts and the pain stops.

The same neurovascular wiring is implicated in migraine aura and throbbing pain. A study in the journal Headache found 17 percent of migraine patients got a headache from one swallow of ice cream, compared with 46 percent of students. In another study, eating ice cream in under five seconds produced headaches in 27 percent of people, versus 12 percent for those who took more than 30 seconds, and children are more prone than adults. The first written account came from Patrick Brydone in the 1770s, describing a British naval officer in Sicily who spat out ice cream with a horrid oath.

• Why cats get brain freeze, and the whisker sensitivity of their trigeminal nerve
• The phrase ice cream headache in 1937, brain freeze in this sense in 1986, and 7-Eleven's trademark
• A competitive ice skater who triggered it by breathing the cold air above the rink
• Awake neurosurgery patients who felt brain freeze when a drill reached the inner table of the skull
• Pressing the tongue to the palate to rewarm the vessels

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Dutch psychiatrist Frederik van Eeden coined the term lucid dream in 1913, borrowing from the psychiatric idea of a lucid interval: the moment a patient regains insight. This episode traces the experience from Aristotle, Galen, and Tibetan Buddhist dream yoga to Samuel Pepys, who wrote in 1665 that he knew a dream about Lady Castlemaine was a dream before he woke. It separates awareness from control using Stephen LaBerge's work, walks through Kristen LaMarca's four skill levels from beginner to expert, and explains Paul Tholey's reflection technique of asking yourself many times a day whether you are dreaming.

Philosopher Norman Malcolm argued no one could prove consciousness during sleep. On April 12, 1975, Keith Hearne answered him: Alan Worsley, paralyzed in REM sleep, moved his eyes in a prearranged left right pattern that appeared on the electrooculogram. LaBerge later found that counting ten seconds in a dream takes ten real seconds, but dream squats take longer. J. Allan Hobson tied lucidity to the dorsolateral prefrontal cortex switching back on, and studies published between 2021 and 2026 describe dreamers solving math problems spoken to them from outside and answering with eye and facial movements.

• Tholey's finding that dream characters can rhyme words but usually fail at arithmetic
• A 2018 double blind trial of galantamine that triggered first ever lucid dreams in 10 participants
• Lucid dreaming treatment for chronic nightmares in PTSD, and Deirdre Barrett's The Committee of Sleep
• Sleep paralysis, reported by about 7.6 percent of people, and its floating, chest pressure, and intruder hallucinations
• The debate over whether lucid dreaming is true sleep or a microawakening

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Henry Gray, born in 1827, was already lecturing on anatomy at St. George's Hospital Medical School in London by 1853, after award winning research on the endocrine glands and the spleen. In 1855 he asked illustrator Henry Vandyke Carter to help him make an anatomy textbook that students could afford and surgeons could use. For 18 months the two dissected unclaimed bodies from workhouses and hospital mortuaries, Gray isolating nerves and vessels while Carter drew them, work made possible by the Anatomy Act of 1832, which ended the reliance on resurrection men. Anatomy, Descriptive and Surgical appeared in London in 1858 from John William Parker and Son, dedicated to Sir Benjamin Collins Brodie, with a second edition in 1860.

In 1861 Gray treated a young nephew with smallpox. The boy survived, but Gray caught the virus and died at 34, a master of visible anatomy undone by an invisible pathogen. The book outlived him and split in two: Blanchard and Lea bought the American rights in 1862, and the US and British edition numbers drifted so far apart that the 30th British edition came out in 1949 and the 30th American edition in 1984. Later editions added histology, embryology, stem cells, and diagnostic radiology, swelling to 2,092 pages by the 38th edition.

• Why legal access to bodies let Gray and Carter work slowly and methodically
• The brief alignment of 1918, when both sides of the Atlantic released a 20th edition
• The 2015 41st edition's sections on fluorescent microscopy and regenerative medicine
• Spin offs like Gray's Anatomy for Students, created to restore the original goal of accessibility
• Susan Standring's 39th edition, which reorganized the book from systemic to regional anatomy

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Before October 16, 1846, surgery meant being strapped to a table fully awake. This episode follows William T.G. Morton, born in Charlton, Massachusetts in 1819, a former clerk and salesman who left the Baltimore College of Dental Surgery without a degree and built a business soldering false teeth to gold plates. To win over the prominent Whitman family of Farmington, Connecticut, he promised to become a physician and enrolled at Harvard, where chemist Charles T. Jackson introduced him to sulfuric ether. In September 1846 he pulled a tooth from Ebenezer Frost without pain, and surgeon Henry Jacob Bigelow arranged a demonstration at Massachusetts General Hospital, where John Collins Warren removed a neck tumor from a silent patient.

Then Morton disguised the ether with aromatic oils, called it Letheon, and patented it, enraging the medical profession. A bitter fight for credit followed with Jackson and his former partner of three weeks, Horace Wells, while Congress stalled on his request for a $100,000 reward. Morton testified erratically in the Webster and Parkman murder trial, then gave ether to more than 2,000 wounded soldiers as a Civil War volunteer. In July 1868 he suffered a stroke in a New York carriage and ran into a Central Park lake before dying at St. Luke's Hospital.

• How ether depresses the cerebral cortex while leaving the brainstem running
• Morton's failed lawsuit against the United States, argued by Richard Henry Dana Jr.
• His widow's three medals, the only rewards she said he ever received
• Crawford Williamson Long's use of ether in Georgia in March 1842, unpublished until 1849
• Boston's ether monument, which shows an anonymous doctor in Moorish robes to avoid choosing sides

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From the 1920s into the 1970s, shoe stores invited children to step onto a polished wooden cabinet, slide their feet into a slot, and watch their own toe bones wiggle in glowing green through one of three viewing portholes, one each for the child, the parent, and the salesperson. This episode tells the story of the shoe fitting fluoroscope, also sold as the pedoscope, and the patent squabble behind it: Boston physician Jacob Lowe sold his rights to the Adrian Company of Milwaukee for $15,000, the Adrian family claimed Matthew Adrian built the first machine, Clarence Karrer said his idea was stolen, and a St. Albans company patented the British Pedoscope in 1924.

The numbers are startling. A typical 20 second viewing delivered an average of 13 roentgens to a customer's feet, and some American machines measured up to 116, while scattered radiation leaked sideways at pelvis height into the clerks who stood beside them all day. A 1948 evaluation found the machines useless for fitting shoes, yet the industry argued they prevented bunions and corns. By the late 1940s about 10,000 were running in the United States. The FDA acted in 1953, Pennsylvania banned them in 1957, the United Kingdom settled for a warning sign in 1958, and Switzerland held out until 1989.

• Why children trying on three or four pairs in an afternoon took repeated doses while being about twice as radiosensitive as adults
• A shoe salesperson's 1950 radiation burn that ended in amputation, and a 2004 report of basal cell carcinoma on a former clerk's sole
• Hermann Joseph Muller's 1927 discovery that radiation causes genetic mutations
• The 1946 suggestion that children use the machines no more than 12 times a year
• A working machine spotted in a Boston store in the late 1970s and Time's 1999 list of the century's worst ideas

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Taphophobia, the fear of being buried alive, was never just Victorian paranoia. This episode explains what actually kills someone trapped in a coffin: carbon dioxide builds up as panic speeds the breathing, and hypercapnia sets in before the oxygen runs out, though a trickle of air through loose soil can stretch survival terrifyingly long. It weighs the legend of the fifth century Emperor Zeno, said to have screamed for three days inside his sarcophagus while Empress Ariadne refused to open it, against folklorist Paul Barber's point that decomposition gases can twist limbs and tear shrouds. Then come the verified cases, including 30 year old Essie Dunbar of South Carolina in 1915, who sat up in her coffin after her sister demanded one last look.

The fear outlived the 1800s. A Massachusetts funeral director found a living person in a body bag in 2001, and a Michigan woman pronounced dead in 2020 was found breathing at the funeral home, because a deeply slowed metabolism can drop below what field monitors detect. Society answered with Irish wakes, Robert Robinson's 1791 glass coffin window, J.G. Krichbaum's 1882 periscope pipe, and the 1896 London Association for the Prevention of Premature Burial. Live burial was also a punishment, from Rome's Vestal Virgins to medieval Germany, and a spectacle, from the yogi Sadhu Haridas to escape artist Bill Shirk.

• The Williamsport, Pennsylvania family of 1890 who built a felt lined vault at Wildwood Cemetery with an air supply and an escape wheel
• Why there is no evidence anyone was ever saved by a safety coffin
• Medieval German executioners driving stakes through buried women so they could not return as undead Wiedergänger
• The legend of St. Oran at Iona, dug up alive and buried again for saying heaven and hell did not exist
• Bill Shirk's 1992 plexiglass coffin collapsing under seven tons of dirt and cement

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In December 1963 and January 1964 in San Diego, 17 year old Point Loma High student Randy Gardner set out to beat the 260 hour sleeplessness record of Tom Rounds of Honolulu, starting with classmates Bruce McAllister and Joe Marciano Jr. keeping him awake. Stanford sleep researcher William Dement flew in, and Lieutenant Commander John J. Ross of the U.S. Navy Medical Neuropsychiatric Research Unit monitored his health. Their accounts split: Dement reported few ill effects and lost to Gardner at pinball on day 10, while Ross recorded mood swings, paranoia, hallucinations of street signs as people, and Gardner's belief that he was Chargers running back Paul Lowe.

On day 11 Gardner was asked to count down from 100 by sevens, stopped at 65 and forgot what he was doing. He finished at 11 days and 25 minutes, about 264.4 hours, told a press conference he wanted to show sleeplessness had no bad effects, then slept 14 hours and 46 minutes. Tests at one, six and ten weeks found no lasting change. Guinness later dropped the category, later claims are hard to verify because of microsleeps, and in 2017 Gardner said that since about 2007 he had suffered severe chronic insomnia he blamed on the 1963 stunt.

• How procedural memory kept his pinball skills while prefrontal working memory failed the math test
• Recovery through deeper slow wave sleep rather than hour for hour payback
• Later claims from Toimi Silvo's 276 hours to a 449 hour rocking chair marathon
• A 2024 livestreamed attempt that ended with welfare checks and an ambulance
• Microsleeps, brief bursts of sleep with eyes open, and why EEG monitoring matters

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Albert Sabin was born Abram Saperstein in 1906 in Bialystok, came to the United States in 1921, and quit dentistry at NYU for medical research, earning his medical degree in 1931. In World War II he served as a major on the Neurotropic Virus Commission, studying dengue and sandfly fever and winning the Legion of Merit. His autopsies had shown that poliovirus enters through the mouth and multiplies in the intestines before reaching the nervous system. So when Jonas Salk's injected, killed virus vaccine was approved in 1955, Sabin argued it protected individuals from paralysis without stopping the virus in the gut, and pushed for a live, weakened oral vaccine instead.

After testing his strains on himself, his family and, in 1954, inmates at the Chillicothe reformatory in Ohio, Sabin was stonewalled at home, so between 1956 and 1960 he worked with Soviet virologists Mikhail Chumakov and Marina Voroshilova. Over 90 million people in the Soviet Union and Eastern Bloc received his vaccine in 1959 and 1960. A spring 1960 trial among 78,000 Cincinnati schoolchildren followed, and the U.S. licensed his strains in 1961 and 1962. Given on sugar cubes to mask its bitterness, the vaccine inspired songwriter Robert Sherman's spoonful of sugar song for Mary Poppins, and Sabin never patented it.

• IgG antibodies in the blood from Salk's shot versus IgA antibodies in the gut from Sabin's drops
• Weakening the virus by passing it repeatedly through monkey cells
• A 1967 trip to Cuba to discuss public health with Fidel Castro
• Serving as president of the Weizmann Institute of Science in Israel
• Paralyzed by spinal calcification in 1983, then restored by surgery at Johns Hopkins in 1992 before his death in 1993