The timeline

Now we know:The square root of negative one, written as i, defines the imaginary unit and extends the real numbers to the complex number system. Complex numbers are physically real in the deepest sense: quantum mechanics cannot be expressed using only real numbers, and electrical engineering, signal processing, and GPS calculations all rely on complex arithmetic. Read more →

Now we know:The Emancipation Proclamation only freed slaves in Confederate-held territories, not in Union border states or areas already under Union control. The 13th Amendment (1865) abolished slavery nationwide. Read more →

Now we know:There is no contemporary evidence linking Betsy Ross to the first flag. The story was promoted by her grandson William Canby in 1870, nearly a century after the supposed event, with no documentation. Read more →

Now we know:0.999... is exactly equal to 1, not approximately equal. They are two representations of the same real number. Since 1/3 = 0.333..., multiplying both sides by 3 gives 0.999... = 1. More formally, the real number system defines a repeating decimal as the limit of its partial sums, and the limit of 0.9, 0.99, 0.999, ... is exactly 1. Read more →

Now we know:Georg Cantor proved in 1891 that there are different sizes of infinity. The set of real numbers is strictly larger than the set of counting numbers, even though both are infinite. His diagonal argument showed that no complete list of real numbers is possible, because a new real number not on any list can always be constructed. Read more →

Now we know:Educated people in medieval Europe knew the Earth was round. The myth was popularized by 19th-century writers (notably Washington Irving) as part of a narrative pitting science against religion. Read more →

Now we know:Light does not require a medium. Einstein's special relativity (1905) and the Michelson-Morley experiment (1887) disproved the aether. Read more →

Now we know:The 180-degree rule holds only in flat Euclidean space. On the surface of a sphere, a triangle with one vertex at the North Pole and two vertices on the equator 90 degrees apart has three right angles, summing to 270 degrees. Einstein's general relativity confirmed that physical space near massive objects is geometrically curved, and light-ray triangles near massive stars do not obey the Euclidean rule. Read more →

Now we know:Centrifugal force is a fictitious (inertial) force - it only appears in rotating reference frames. The real force is centripetal, pulling inward. Read more →

Now we know:Bulls are colorblind to red. They react to the movement of the matador's cape, not its color. The cape is red for tradition and to hide blood stains. Read more →

Now we know:There are at least four fundamental states (solid, liquid, gas, plasma), plus many others like Bose-Einstein condensates, superfluids, and more. Read more →

Now we know:Electrons occupy probabilistic orbitals, not fixed circular paths. The quantum mechanical model had superseded the Bohr model by the late 1920s but textbook diagrams lagged far behind. Read more →

Now we know:Shaving only cuts hair at the surface. It does not affect growth rate, thickness, or color. The blunt tip may feel coarser temporarily. Read more →

Now we know:Hair and nails do not grow after death. The skin around them retracts due to dehydration, creating the illusion of growth. Cell division in hair follicles and nail matrices stops within minutes of circulation ceasing. Read more →

Now we know:Lightning frequently strikes the same place multiple times. Tall structures like the Empire State Building are struck dozens of times per year. Read more →

Now we know:Gödel's 1931 incompleteness theorems proved this impossible. Any consistent formal system powerful enough to express basic arithmetic contains true statements that cannot be proved within that system. No set of axioms can be simultaneously complete and consistent. Read more →

Now we know:Einstein excelled in mathematics from an early age. He taught himself calculus by age 12 and was doing advanced math before most students. The myth conflates a change in grading systems. Read more →

Now we know:A 1930s decimal point error made spinach appear to have 10x more iron than it actually does. Spinach contains oxalates that inhibit iron absorption. It is not exceptionally high in bioavailable iron. Read more →

Now we know:By modern definition, 1 is not prime. Primality requires exactly two distinct positive divisors, and 1 has only one: itself. The exclusion preserves the Fundamental Theorem of Arithmetic, which states that every integer greater than 1 has a unique prime factorization. If 1 were prime, 12 could be factored as 2x2x3 or as 1x2x2x3 or 1x1x2x2x3, making factorizations non-unique. Read more →

Now we know:Vitamin A deficiency can impair night vision, but eating extra carrots beyond normal dietary levels does not enhance vision in people who are not deficient. The myth was WWII propaganda to hide radar technology. Read more →

Now we know:The Great Wall is very difficult to see with the naked eye from low Earth orbit and is not visible from the Moon. Many structures (cities, highways, airports) are more visible. Read more →

Now we know:Alcohol causes blood vessels to dilate, creating a warm feeling on the skin but actually increasing heat loss from the core body. It increases hypothermia risk. Read more →

Now we know:Antibiotics target bacteria, not viruses. Colds and flu are caused by viruses. Taking antibiotics for viral infections contributes to antibiotic resistance without helping the patient. Read more →

Now we know:Camels store fat in their humps, not water. Water conservation comes from efficient kidneys, concentrated urine, and tolerance to dehydration. Read more →

Now we know:There is no medical basis for this saying. Adequate nutrition and hydration are important during any illness. The saying dates to the 1500s and has no scientific support. Read more →

Now we know:Neanderthals had larger brains than modern humans, made sophisticated tools, created art, buried their dead, and interbred with Homo sapiens. Most non-African humans carry 1-4% Neanderthal DNA. Read more →

Now we know:Ostriches do not bury their heads in the sand. When threatened, they lie flat on the ground or run. The myth likely arose from their nesting behavior (turning eggs in the sand) or from seeing them lying low with heads near the ground. Read more →

Now we know:Colds are caused by viruses (rhinoviruses, coronaviruses, etc.), not by being cold or wet. Cold weather may slightly weaken immune response or keep people indoors where viruses spread more easily. Read more →

Now we know:Mental illness involves biological, neurological, genetic, and environmental factors. The biomedical model gained formal footing with the first DSM in 1952 and grew more sophisticated with neuroscience. Read more →

Now we know:The central dogma of molecular biology - DNA → RNA → protein - was proposed by Crick in 1957 and describes how genetic information flows in living cells. The genetic code was being deciphered through 1959–1961. Read more →

Now we know:DNA is the molecule of heredity. Watson and Crick described its double-helix structure in April 1953, but this discovery took years to reach K-12 curricula. Read more →

Now we know:Type 2 diabetes is caused by a combination of genetic factors, insulin resistance, and overall metabolic health. While excessive sugar consumption contributes to obesity (a risk factor), sugar itself does not directly cause diabetes. Type 1 diabetes is an autoimmune condition unrelated to diet. Read more →

Now we know:There is no evidence Marie Antoinette ever said this. The quote was attributed to 'a great princess' by Rousseau in 1766, when she was only 10. It was likely revolutionary propaganda. Read more →

Now we know:Polio is caused by poliovirus and spread via the fecal-oral route. Prevention requires vaccination (Salk, 1955; Sabin oral, 1961), not avoidance of pools or heat. Read more →

Now we know:Earth is approximately 4.54 billion years old. Clair Patterson established this in 1956 using uranium-lead isotope ratios in meteorite samples. Read more →

Now we know:There is no proven safe threshold of ionizing radiation. Fallout from atmospheric tests in the 1950s exposed millions to radiation and caused measurable increases in cancer rates. Read more →

Now we know:Earth orbit is achievable with sufficient rocket velocity (~7.9 km/s). The Soviet Sputnik 1 achieved orbit on October 4, 1957, making this the first artificial satellite - proving orbital spaceflight was possible. Read more →

Now we know:Space contains plasma, gas, dust, cosmic rays, magnetic fields, and electromagnetic radiation. Luna 1 (1959) directly measured the solar wind - a continuous stream of charged particles from the sun. Read more →

Now we know:Blood is always red. Deoxygenated blood is dark red, not blue. Veins appear blue through skin due to light scattering and tissue absorption. Read more →

Now we know:Indigenous peoples had inhabited the Americas for at least 15,000 years before Columbus. Leif Erikson reached North America around 1000 CE. Columbus's voyages opened sustained European contact but he discovered nothing that wasn't already inhabited. Read more →

Now we know:A desk provides no meaningful protection against a nuclear detonation. The civil defense campaign offered a false sense of control over a threat no classroom shelter could realistically address. Read more →

Now we know:Large thermonuclear weapons cause destruction on a scale that renders most civil defense measures ineffective for those near blast zones. The Cuban Missile Crisis (October 1962) brought this reality to the brink of lived experience. Read more →

Now we know:Pterosaurs were flying reptiles, not dinosaurs. Dinosaurs belong to the clade Dinosauria; pterosaurs belong to Pterosauria. They are close relatives but distinct groups. Read more →

Now we know:Norse explorers established a settlement at L'Anse aux Meadows in Newfoundland around 1000 CE. Evidence suggests further exploration southward. They did not 'vanish' - the settlement was abandoned, likely due to conflict with Indigenous peoples and limited resources. Read more →

Now we know:There is no archaeological evidence that Vikings wore horned helmets in battle. The image comes from 19th-century Romantic art and opera costumes. Read more →

Now we know:Yuri Gagarin completed a full orbit of Earth on April 12, 1961 - while many of this cohort were still in school. Alan Shepard became the first American in space on May 5, 1961. Read more →

Now we know:Thalidomide caused severe birth defects (phocomelia) in over 10,000 children in Europe and elsewhere. FDA official Frances Kelsey blocked US approval, sparing the US from the worst. The crisis led to the 1962 Kefauver-Harris Amendment requiring proof of drug efficacy and safety. Read more →

Now we know:Smoking causes lung cancer, cardiovascular disease, and COPD. The science was conclusive by the 1964 Surgeon General's report. The apparent 'debate' was manufactured by the tobacco industry — their own scientists had confirmed the cancer link internally by 1953. Read more →

Now we know:The universe began in a hot, dense state approximately 13.8 billion years ago (the Big Bang). The Cosmic Microwave Background, discovered in 1965, confirmed this. Fred Hoyle, who coined 'Big Bang' mockingly, never fully accepted the evidence. Read more →

Now we know:Plate tectonics, established as scientific consensus by 1966-1968, shows that continents ride on rigid plates driven by mantle convection. Seafloor spreading at mid-ocean ridges creates new crust and pushes plates outward at roughly the rate a fingernail grows. Wegener's core insight was right; the mechanism came from the ocean floor, not from him. Read more →

Now we know:Heart transplantation is possible. Dr. Christiaan Barnard performed the first successful human heart transplant in Cape Town on December 3, 1967. Immunosuppressive drug advances made long-term survival achievable. Read more →

Now we know:Early color CRT televisions (particularly GE's 1967 recall) did emit low levels of X-ray radiation at close range. Modern concerns shifted to non-ionizing blue light and screen time effects on vision development in children. Read more →

Now we know:Many dinosaurs were warm-blooded (endothermic) or had intermediate metabolisms. Evidence includes bone structure, growth rates, and the discovery of feathered dinosaurs in cold climates. Read more →

Now we know:LSD can trigger persistent psychotic episodes in vulnerable individuals and cause HPPD (hallucinogen persisting perception disorder). While some therapeutic research was legitimate, the risks were poorly understood and seriously underplayed in early 1960s research. Read more →

Now we know:Lead is a potent neurotoxin, especially harmful to children's brain development. Leaded gasoline was phased out starting in the 1970s, and lead paint was banned in 1978 in the US. Read more →

Now we know:The Moon has significant scientific interest: it records early solar system history, contains water ice in permanently shadowed craters, has Helium-3 deposits, and its regolith chemistry reveals much about planetary formation. Apollo 8 (December 1968) brought humanity's first direct view of lunar surface from orbit. Read more →

Now we know:Most bats can see reasonably well and use vision alongside echolocation. The phrase 'blind as a bat' is entirely false. Read more →

Now we know:Memory is reconstructive, not reproductive. Each recall reshapes a memory. False memories can be implanted through suggestion. Elizabeth Loftus's research from the 1970s onward demonstrated memory's malleability. Read more →

Now we know:The Van Allen radiation belts and solar particle events posed genuine radiation hazards. Apollo trajectories were specifically designed to minimize belt transit time, and NASA tracked radiation doses carefully. A major solar particle event during a lunar transit could have been fatal; astronauts were fortunate none occurred. Post-mission analyses showed some Apollo astronauts received doses approaching occupational safety limits. Read more →

Now we know:Moss grows wherever moisture and shade are sufficient. These conditions depend on local terrain, tree canopy, prevailing wind, and microclimate. Moss distribution does not reliably indicate compass direction. Read more →

Now we know:True eidetic memory (photographic recall) has never been reliably demonstrated in adults. Hyperthymesia (highly superior autobiographical memory) is real but extremely rare. Most 'photographic memory' claims are explainable by trained mnemonic techniques. Read more →

Now we know:Washington's dentures were constructed from combinations of human teeth, animal teeth (cow, horse), hippopotamus ivory, elephant ivory, and lead alloy. No wood was used. The myth likely arose from the staining and darkening of ivory. Read more →

Now we know:Asbestos fibers cause mesothelioma, lung cancer, and asbestosis. Industry documents from the 1930s onward show manufacturers knew of the risks and concealed them. The EPA began restricting asbestos in 1971. Read more →

Now we know:Independent random events have no memory. A fair coin's probability of landing heads is exactly 50% regardless of any preceding streak. The law of large numbers describes proportions converging over enormous sample sizes but makes no promise about any individual event or short sequence. Read more →

Now we know:The Pentagon Papers (published June 1971) revealed that multiple administrations had systematically misled the public and Congress about Vietnam War objectives and prospects. The government had known the war was unwinnable years before admitting it. Read more →

Now we know:DDT bioaccumulates in the food chain and causes reproductive failure in predatory birds through eggshell thinning. The EPA banned it in June 1972 after formal hearings concluded the ecological evidence was sufficient — bald eagle and peregrine falcon populations began recovering once the ban took effect. Read more →

Now we know:Women are fully capable of strenuous athletic competition. There are no physiological reasons to exclude women from endurance sports. Title IX was signed June 23, 1972, prohibiting sex discrimination in federally funded education programs including athletics. Read more →

Now we know:Homosexuality is a normal variation of human sexuality. The American Psychiatric Association removed it from the DSM in 1973. Conversion therapy has since been shown to cause harm with no demonstrated benefit. Read more →

Now we know:Eyewitness memory is highly malleable. Post-event information, stress, question framing, and lineup procedures can distort memory and produce confident but false recollections. Read more →

Now we know:No one was burned at Salem. Nineteen people were hanged, one was pressed to death with stones, and several died in jail. Burning was the European punishment, not the American one. Read more →

Now we know:All taste types can be detected across the entire tongue. The taste map was based on a misreading of a 1901 German study. A fifth basic taste, umami, also exists and was not recognized in Western curricula until much later. Read more →

Now we know:The liver, kidneys, lungs, and skin already detoxify the body effectively. There is no scientific evidence that detox diets, cleanses, or supplements remove toxins better than these organs do. Read more →

Now we know:The domino theory oversimplified revolutionary movements as monolithic communist spread. Vietnam fell in 1975 but most predicted dominoes did not fall. Read more →

Now we know:A 1967 Science paper by Cohen et al. claiming LSD caused chromosomal breaks was widely publicized but was poorly controlled and not replicated. Subsequent research found no consistent evidence of chromosomal damage from LSD at typical doses. Read more →

Now we know:Clinical trials have found no consistent evidence that vitamin C prevents colds in the general population, though it may modestly reduce duration. Megadose supplementation can cause kidney stones and other complications. Read more →

Now we know:The rushed 1976 swine flu vaccine program was associated with approximately 450 cases of Guillain-Barré syndrome - a serious neurological condition - out of 45 million vaccinated. The feared pandemic never materialized. The program was halted in December 1976. Read more →

Now we know:The Apple II launched in 1977, the same year this cohort graduated. The Commodore PET and TRS-80 also launched that year. Personal computing was already arriving. Within a decade, computers were in millions of homes and schools. Read more →

Now we know:Watergate was a broad conspiracy involving the Nixon White House, involving obstruction of justice, abuse of power, campaign finance violations, and use of intelligence agencies against political opponents. Nixon resigned August 9, 1974. Read more →

Now we know:Evolution is a branching bush, not a ladder. Humans and modern apes share a common ancestor; we did not evolve from any modern ape species. Read more →

Now we know:Lead paint poses risks even when not visibly deteriorating - dust from normal wear, opening windows, and renovations releases lead particles. The Consumer Product Safety Commission banned lead paint in US residential settings in 1978. Read more →

Now we know:Love Canal demonstrated that improperly stored chemical waste causes serious health damage to communities above and adjacent to dump sites. The Superfund program (CERCLA, 1980) was created directly in response. Read more →

Now we know:In vitro fertilization (IVF) is possible. Louise Brown, the first IVF baby, was born July 25, 1978 - while students graduating that year were in their last summer of high school. Read more →

Now we know:The animal taught in schools as Brontosaurus was the same animal as Apatosaurus. Elmer Riggs showed in 1903 that Marsh had named both from the same material; under nomenclature rules the older name, Apatosaurus (1877), takes priority. Natural history museums corrected their labels in the late 1970s. A 2015 phylogenetic study by Tschopp and colleagues proposed reinstating Brontosaurus as a valid genus based on new specimen analysis, but the correction schools taught for four decades — that the iconic 'Brontosaurus' was actually Apatosaurus — was accurate. Read more →

Now we know:Nuclear power carries real risks including core meltdowns (Three Mile Island 1979, Chernobyl 1986, Fukushima 2011), radioactive waste storage challenges, and catastrophic failure modes. The 'too cheap to meter' quote was taken out of context but reflected genuine 1950s–60s optimism. Read more →

Now we know:Fat-soluble vitamins (A, D, E, K) accumulate in tissue and are toxic in excess. Even some water-soluble vitamins cause harm at high doses (e.g., B6 neuropathy, vitamin C kidney stones). Megadose vitamin therapy is not supported by clinical evidence. Read more →

Now we know:Chameleons change color mainly for communication (mood, temperature, mating signals) and social interaction. Camouflage is a secondary function at best. Read more →

Now we know:HIV is transmitted through specific bodily fluids: blood, semen, vaginal fluids, rectal fluids, and breast milk. It cannot be transmitted through casual contact, saliva, air, or water. Read more →

Now we know:Most peptic ulcers are caused by H. pylori bacterial infection or NSAIDs. Established by Marshall and Warren in 1982–1984. Read more →

Now we know:HIV is transmitted through specific bodily fluids regardless of sexual orientation. By 1993 over 190,000 Americans had died. Tom Hanks won the Oscar for Philadelphia (1993), bringing AIDS to mainstream visibility - but school health curricula still lagged. Read more →

Now we know:The scientific consensus through the 1970s actually favored warming from CO2 emissions, though some papers did address aerosol-driven cooling. The 'global cooling' narrative was a media oversimplification. By the 1980s the warming signal was dominant in scientific literature. Read more →

Now we know:The Antarctic ozone hole was confirmed by the British Antarctic Survey in 1985. The Montreal Protocol was signed in 1987, establishing global CFC phase-outs. The ozone hole is now recovering. This was a rare environmental success story. Read more →

Now we know:Space Shuttle Challenger broke apart 73 seconds after launch on January 28, 1986, killing all seven crew members. The cause was an O-ring failure in cold weather - a known risk that engineers had warned about and management overrode. Read more →

Now we know:The American Physical Society's 1987 report concluded that SDI was at least a decade from even beginning meaningful tests. The technology Reagan described did not exist and no comprehensive missile defense system exists today. Read more →

Now we know:Pons and Fleischmann's March 1989 cold fusion announcement was not reproducible. The scientific community found no credible evidence of fusion. Cold fusion is widely regarded as pathological science - a case study in how extraordinary claims must meet extraordinary evidence standards. Read more →

Now we know:Dogs see colors, but their spectrum is limited compared to humans. They see shades of blue and yellow but cannot distinguish red and green. Read more →

Now we know:The Exxon Valdez spill (March 24, 1989) in Prince William Sound, Alaska released 11 million gallons of crude oil. Response was chaotic and insufficient. Over 1,300 miles of coastline were oiled and wildlife damage persisted for decades. Read more →

Now we know:Decades of research in ethology and comparative psychology have documented complex emotions, long-term memory, social learning, and problem-solving across many animal species. Read more →

Now we know:Switching wins 2/3 of the time, not 1/2. The host always opens a losing door he already knows about, which preserves the contestant's original 1/3 probability on the chosen door and concentrates the remaining 2/3 on the other door. Computer simulations and mathematical proofs both confirm this, and the controversy was definitively settled by the mid-1990s. Read more →

Now we know:The 'rising tide of mediocrity' described in A Nation at Risk has been substantially contested. Subsequent research found that NAEP scores had been relatively stable and that the report's data was selectively presented to support a policy agenda of school choice and standardization. Read more →

Now we know:Virtually all brain regions have identified functions and show activity throughout the day. The 10% figure has no basis in neuroscience. Read more →

Now we know:Decades of economic research found limited trickle-down effects. Economic inequality grew substantially during and after periods of supply-side policy. Reagan's own budget director David Stockman privately called it a 'Trojan horse' for cutting top tax rates. Read more →

Now we know:Chernobyl released contamination across Europe. WHO estimates up to 4,000 additional cancer deaths may result from radiation exposure. The full health and environmental impact has been debated for decades, with some estimates far higher. Read more →

Now we know:The MBTI has poor test-retest reliability: roughly half of respondents get a different type when retested a few weeks later. Systematic reviews find it does not predict job performance, academic outcomes, or relationship success better than chance. Read more →

Now we know:The Soviet Union dissolved in December 1991. Gorbachev's reforms accelerated rather than prevented collapse, and the Cold War order taught as permanent vanished within a few years. Read more →

Now we know:Body temperature varies by person, time of day, and measurement method. A 2020 study found the average is closer to 97.5°F (36.4°C) and has been declining slightly over time. Read more →

Now we know:While metal in a microwave can cause sparks and fire under certain conditions, smooth metal objects (like a spoon in a cup) are often safe. The danger depends on shape, edges, and the presence of arcing paths. Read more →

Now we know:Biological sex is a spectrum involving chromosomes, hormones, anatomy, and genetics. Intersex conditions occur in approximately 1.7% of births. The SRY gene is the primary determinant, but exceptions exist. Read more →

Now we know:Early margarines contained trans fats, which are more harmful than the saturated fat in butter. Modern margarines have improved but are still highly processed. Butter in moderation is now considered acceptable by many nutritionists. Read more →

Now we know:Multiple large-scale evaluations found that DARE (Drug Abuse Resistance Education), launched in 1983, had no statistically significant effect on youth drug use rates. Peer-reviewed studies, a GAO review, and federal public health authorities concluded it was ineffective in its original form. Read more →

Now we know:Gulf War Syndrome is now recognized as a genuine multi-symptom illness affecting an estimated 175,000–250,000 veterans. Causes under investigation include exposure to chemical agents, depleted uranium, pesticides, and nerve agent prophylactics. Read more →

Now we know:Memory is reconstructive. The 'repressed memory' model lacks scientific support. Therapy techniques used to 'recover' memories frequently created false memories instead, leading to wrongful accusations and convictions. The recovered memory movement peaked in the late 1980s–early 1990s. Read more →

Now we know:Revere and other riders used discretion to avoid British patrols. Revere likely said 'the regulars are coming out.' Multiple riders participated. Revere was captured before reaching Concord. Read more →

Now we know:Controlled studies show no consistent causal link between sugar and hyperactivity. Parental expectations likely explain the perceived effect. Read more →

Now we know:HAART (highly active antiretroviral therapy) was introduced in 1996 and transformed AIDS from a death sentence into a manageable chronic condition. People on modern HIV treatment now have near-normal life expectancy. Read more →

Now we know:Birds are living dinosaurs — the only surviving lineage of theropod dinosaurs. Feathered fossil discoveries beginning in 1996 confirmed that feathers evolved well before flight and were widespread across theropod lineages. Read more →

Now we know:Cannabis has established medical applications including pain management, nausea reduction, and treatment of certain seizure disorders. As of 2025, it is legal for medical use in most US states. Read more →

Now we know:Race is primarily a social construct. Genetic variation within populations far exceeds variation between them — approximately 85% of all human genetic variation occurs within conventionally defined racial groups, not between them. There is no scientific basis for racial hierarchy in cognition or ability. Group IQ score gaps are fully explained by socioeconomic factors, educational access, test design, stereotype threat, and the Flynn effect — not genetics. The APA's 1996 task force found no evidence for genetic explanations of group differences. Read more →

Now we know:Cloning produces a genetic copy but not an identical individual. Epigenetics, developmental variation, and environment mean cloned animals differ from their genetic source in appearance, behavior, and health. Dolly the sheep (born July 1996, announced February 1997) was the first cloned mammal from an adult cell. Read more →

Now we know:Neurogenesis (new neuron growth) occurs in the adult hippocampus and possibly other regions. The brain is plastic throughout life. Read more →

Now we know:No study has found a causal link between knuckle-cracking and arthritis. One doctor cracked only one hand's knuckles for 50 years with no difference. Read more →

Now we know:Most marijuana users do not progress to harder drugs. The gateway hypothesis confuses correlation with causation and ignores the role of alcohol and tobacco as more common prior substances. Read more →

Now we know:The 1993 Rauscher et al. study showed a modest, short-lived (10–15 minute) boost in one spatial task in college students - not babies, not general intelligence, and not lasting. The broader 'Mozart Effect' claimed for infant brain development was never supported by research. Read more →

Now we know:Chewing gum passes through the digestive system normally. It is not digestible but is excreted like other indigestible materials. Read more →

Now we know:The number of bones varies individually. Many adults have extra ribs, sesamoid bones, or fused/split bones. The exact count ranges from 206 to over 270 in infants whose bones haven't fused. Read more →

Now we know:Internet activity leaves extensive digital traces - IP addresses, browser fingerprints, cookies, ISP logs, and server logs. This was true from the internet's inception. The expectation of anonymity was always a misconception. Read more →

Now we know:The saccharin-cancer link came from rat studies using extreme doses via a mechanism specific to rats. It is not carcinogenic to humans at normal consumption levels. Removed from the US carcinogen list in 2000. Read more →

Now we know:Y2K was a real software problem that required significant remediation. However, the scale of societal collapse predicted by the most alarmist voices did not materialize. Countries that did less remediation (e.g., Italy) experienced minimal problems. Read more →

Now we know:Poverty and environmental deprivation were found to be more predictive of developmental outcomes than prenatal cocaine exposure. The crack baby narrative was substantially overstated. Read more →

Now we know:Velociraptors were turkey-sized, about 2 feet tall. Jurassic Park used Deinonychus as the model but called them Velociraptors because the name sounded better. Read more →

Now we know:Water needs vary by individual, activity level, climate, and diet. There is no universal requirement. The '8x8 rule' has no scientific basis. Read more →

Now we know:Bacteria transfer to food almost instantly upon contact. The '5-second rule' has no scientific basis. Read more →

Now we know:Goldfish can remember things for months, recognize their owners, and learn complex tasks. Read more →

Now we know:Most traits and diseases are polygenic—shaped by hundreds of genes interacting with each other and the environment. The 98% of the genome once dismissed as 'junk DNA' turned out to contain regulatory elements essential to gene expression. Read more →

Now we know:The internet became the defining infrastructure of the 21st-century economy. Amazon, eBay, Yahoo, and Hotmail all launched in 1995–96. The dot-com crash eliminated overvalued companies but not the internet itself — by 2020, five of the ten largest companies by market cap were internet businesses. Read more →

Now we know:Scientific consensus on human-caused climate change was already well established by 2001, and the IPCC's 2007 Fourth Assessment Report called warming 'unequivocal.' The appearance of major scientific debate was largely manufactured by fossil fuel interests and amplified through politics and media. Read more →

Now we know:No weapons of mass destruction were found in Iraq after the 2003 invasion. The intelligence was flawed, misrepresented, and in some cases fabricated. The Iraq Survey Group concluded Saddam had ended his WMD programs in 1991. Read more →

Now we know:The Kyoto Protocol had significant limitations: the US never ratified it, China and India were exempt as 'developing' nations, and overall global emissions continued rising. The Paris Agreement (2015) attempted a more comprehensive approach. Read more →

Now we know:Pluto was reclassified as a dwarf planet by the IAU in 2006. The solar system now has 8 recognized planets. Read more →

Now we know:Dale's Cone was originally about instructional media, not retention percentages. The specific percentages were added later by anonymous sources and have no scientific basis. Read more →

Now we know:Multiple large-scale studies found that abstinence-only programs do not delay sexual initiation, reduce teen pregnancy, or lower STI rates compared to comprehensive sex education. Some studies found higher rates of unprotected sex among abstinence-pledgers. Read more →

Now we know:Reading in low light causes temporary eye strain but does not cause permanent damage to eyesight. Read more →

Now we know:Male pattern baldness is polygenic, involving variants from both maternal and paternal chromosomes. The androgen receptor gene on the X chromosome plays a significant role but multiple loci on autosomes also contribute. Read more →

Now we know:Life-cycle analysis found that corn ethanol produced comparable or greater greenhouse gas emissions than gasoline when land-use change was included. The biofuel mandate drove up global food prices and contributed to food insecurity in developing nations. Read more →

Now we know:The deregulation of the 1990s and 2000s, combined with inadequate oversight of mortgage-backed securities and credit default swaps, produced the worst financial crisis since the Great Depression. Lehman Brothers collapsed September 15, 2008. The crisis erased $11 trillion in household wealth. Read more →

Now we know:The US housing market peaked in 2006 and began falling in 2007. The subsequent collapse wiped out trillions in household wealth, triggered the worst financial crisis since the Great Depression, and produced the largest foreclosure wave in American history. Read more →

Now we know:The government allowed Lehman Brothers - then the fourth-largest US investment bank - to fail on September 15, 2008. The failure triggered a global credit freeze. The claim that other institutions were 'too big to fail' was confirmed when the government then did intervene for AIG, Citigroup, and others - but the inconsistency revealed there was no coherent policy. Read more →

Now we know:No reliable biological evidence supports innate female inferiority in rationality or mathematical ability. Performance gaps largely disappear when controlling for socialization and stereotype threat, and have narrowed dramatically wherever structural barriers have been removed. Read more →

Now we know:There is no scientific evidence supporting the 'learning styles' hypothesis. Teaching to a preferred style does not improve outcomes. Read more →

Now we know:Humans have far more than five senses. Scientific consensus recognizes at least 20, including proprioception (body position), equilibrioception (balance), nociception (pain), thermoception (temperature), and interoception (internal body states). Read more →

Now we know:Active recall, spaced repetition, and interleaved practice are more effective than simple repetition. Learning science emphasizes understanding over rote memorization. Read more →

Now we know:Andrew Wakefield's 1998 Lancet paper claiming an MMR-autism link was based on fraudulent data involving only 12 children. The paper was retracted in 2010. Wakefield lost his medical license for ethical violations. Over 20 large-scale studies involving millions of children found no link between the MMR vaccine and autism. Read more →

Now we know:PEMDAS is a convention, not a natural law. In some countries and contexts, different conventions exist. The ambiguity of expressions like 8÷2(2+2) reveals that implicit multiplication and division left-to-right can produce different answers depending on convention. Read more →

Now we know:T-Rex arms were surprisingly strong and muscular. They may have been used for grasping prey, mating, or helping the animal rise from a prone position. Read more →

Now we know:Decades of research failed to find a consistent causal link between violent games and real-world violence. Read more →

Now we know:The pyramid promoted refined carbohydrate overconsumption. Nutrition researchers increasingly criticized it as industry-influenced. Harvard's Healthy Eating Pyramid proposed an alternative in 2003. Read more →

Now we know:Nuclear power has one of the lowest death tolls per unit of energy produced. Coal and oil cause far more deaths from air pollution, accidents, and climate change. Even including Chernobyl and Fukushima, nuclear is statistically safer than fossil fuels. Read more →

Now we know:Both hemispheres work together. Functions are not neatly divided by personality type. Read more →

Now we know:Multiple post-9/11 reviews found that bulk metadata collection programs (NSA's Section 215 program) produced no cases where bulk surveillance was essential to preventing an attack. The Privacy and Civil Liberties Oversight Board concluded in 2014 that the program was illegal and ineffective. Read more →

Now we know:Dietary cholesterol has limited effect on blood cholesterol in most people. Eggs are nutritious. The 2015 Dietary Guidelines Advisory Committee removed the longstanding dietary cholesterol limit. Read more →

Now we know:Fat quality matters more than fat quantity. Unsaturated fats (olive oil, nuts, fish) are beneficial; trans fats are harmful; saturated fat's role is more nuanced than once believed. The low-fat movement inadvertently engineered a massive increase in refined carbohydrate and sugar consumption, contributing to rising obesity rates. The total fat restriction that governed federal dietary policy since 1977 was quietly removed in the 2015 Dietary Guidelines. Read more →

Now we know:Only about 9% of plastic ever produced has been recycled. Most is landfilled, incinerated, or enters the environment. Recycling symbols on plastic are resin identification codes, not recyclability guarantees. Read more →

Now we know:Research has linked heavy social media use to increased rates of anxiety, depression, and loneliness in adolescents. Algorithmic amplification of outrage and comparison-driving content have measurable effects on wellbeing. Read more →

Now we know:Meta-analyses show mixed results for growth mindset interventions. The effect sizes are often small, and the dichotomy oversimplifies human motivation and learning. Read more →

Now we know:Randomized controlled trials show no consistent effect of breakfast on weight loss when total calorie intake is controlled. The 2014 BREAK trial found no significant difference in weight loss between adults who ate or skipped breakfast. The phrase 'most important meal of the day' originated in cereal industry marketing, not clinical research. Read more →

Now we know:COVID-19 spreads through both aerosols (small airborne particles) and droplets. Surface transmission (fomites) was overstated. Masks significantly reduce transmission. Read more →

Now we know:The evidence for red wine's heart benefits is weak and confounded by lifestyle factors. The 'French Paradox' was largely based on flawed data. Any potential benefits are outweighed by the known harms of alcohol. Read more →