Facts That Changed Since You Were in School

  1. Graduated in 1965
  2. 74 major discoveries since your graduation
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  • Technology & Computing
2020

Paper Will Be Completely Replaced by Computers

What you learned in school:

Technology classes predicted the "paperless office" where all documents would be digital and paper would become completely obsolete. Students learned about a future without physical documents, books, or written materials of any kind. Textbooks described computers as making paper unnecessary for all communication, record-keeping, and information storage. The vision was of offices and schools operating entirely through digital screens and electronic files, with paper relegated to museums as an outdated technology.

What we know now:

Technology classes predicted the "paperless office" where all documents would be digital and paper would become obsolete. Students learned about a future without physical documents, books, or written materials. Paper consumption actually increased with the adoption of personal computers and printers, as people printed digital documents. While digital documents are now common, paper remains important for legal documents, books, note-taking, and many other applications. The prediction failed to account for the continued advantages of paper for certain tasks and the human preference for physical documents in many situations.
  • Technology & Computing
2020

Virtual Reality Will Replace All Entertainment

What you learned in school:

Technology classes in the 1990s predicted that virtual reality would become the dominant form of entertainment, completely replacing television, movies, and books. Students learned about immersive virtual worlds as the inevitable future of all media consumption. Textbooks described VR as revolutionary technology that would make traditional entertainment obsolete. The predictions assumed that technical limitations would be quickly overcome and that people would prefer virtual experiences over all other forms of entertainment.

What we know now:

Technology classes predicted that virtual reality would become the dominant form of entertainment, replacing television, movies, and books. Students learned about immersive virtual worlds as the future of media consumption. While VR technology has advanced significantly, it remains a niche entertainment option rather than replacing traditional media. Issues with motion sickness, cost, social isolation, and content limitations have prevented widespread adoption. Most people still prefer traditional entertainment forms for daily use, though VR has found success in specific applications like gaming and training.
  • Technology & Computing
2020

Email Will Kill Postal Mail

What you learned in school:

Technology and business classes predicted that electronic mail would completely replace physical postal services within a few decades. Students learned about the inevitable obsolescence of traditional mail delivery as digital communication became dominant. Textbooks described postal workers and mail trucks as relics of the past that would disappear once everyone had access to email. The prediction assumed that all communication needs could be met electronically, making physical mail delivery unnecessary and economically unviable.

What we know now:

Technology and business classes predicted that electronic mail would completely replace physical postal services. Students learned about the obsolescence of traditional mail delivery. While email has dramatically reduced personal letter writing and some business correspondence, postal services have adapted and continue to thrive with package delivery, e-commerce fulfillment, and specialized services. Online shopping has actually increased package delivery demand. Postal services evolved rather than disappeared, finding new roles in the digital economy.
  • Psychology & Social Sciences
2010

Boys and Girls Learn Differently Due to Brain Differences

What you learned in school:

Educational psychology textbooks taught that boys and girls had fundamentally different learning styles due to biological brain differences. Students learned about "boy brains" versus "girl brains" with distinct educational needs requiring different teaching approaches. This was used to justify single-sex education and gender-specific curricula.

What we know now:

Educational psychology taught that boys and girls had fundamentally different learning styles due to biological brain differences. Students learned about "boy brains" and "girl brains" with distinct educational needs. While there are some statistical differences between male and female brains, most cognitive and learning differences between boys and girls result from socialization, cultural expectations, and educational practices rather than inherent biological differences. Brain plasticity means that environmental factors strongly influence development. Single-sex education based on supposed brain differences has not shown consistent benefits.
  • Nutrition & Health
2010

Eating Eggs Raises Cholesterol Dangerously

What you learned in school:

Health classes taught that eating eggs, especially egg yolks, would directly raise blood cholesterol levels and significantly increase heart disease risk. Students learned to limit eggs to no more than a few per week to prevent cardiovascular problems. Nutrition textbooks listed eggs as high-cholesterol foods to avoid, similar to fatty meats. The dietary guidelines emphasized that all cholesterol-containing foods should be minimized, with eggs being a primary target for restriction due to their high cholesterol content.

What we know now:

Health classes taught that eating eggs, especially egg yolks, would directly raise blood cholesterol levels and increase heart disease risk. Students learned to limit eggs to prevent cardiovascular problems. For most people, dietary cholesterol has minimal impact on blood cholesterol levels. The liver produces most of the body's cholesterol and adjusts production based on dietary intake. Eggs contain beneficial nutrients including protein, vitamins, and healthy fats. Recent dietary guidelines have removed limits on dietary cholesterol for healthy individuals. The connection between dietary cholesterol and blood cholesterol was oversimplified.
  • Nutrition & Health
2010

Breakfast Is the Most Important Meal

What you learned in school:

Health and nutrition classes taught that breakfast was the most important meal of the day, essential for health, weight management, and cognitive function. Students learned that skipping breakfast would slow metabolism, cause weight gain, and impair academic performance. Textbooks emphasized that everyone needed to eat breakfast to start their day properly, regardless of individual preferences or hunger levels. This was presented as established nutritional science with no discussion of individual variation or alternative eating patterns.

What we know now:

Health and nutrition classes taught that breakfast was essential for health, weight management, and cognitive function. Students learned that skipping breakfast would slow metabolism and lead to overeating later. This was presented as established scientific fact. The "most important meal" concept was largely created by cereal companies and breakfast food marketers. Research shows that meal timing is less important than total daily nutrition. Some people function better with breakfast, others don't. Intermittent fasting research suggests that breakfast isn't necessary for everyone. The importance of breakfast was overstated for commercial rather than scientific reasons.
  • Technology & Computing
2010

Video Calling Will Never Be Practical

What you learned in school:

Technology classes taught that video calling was an interesting novelty but would never be practical for everyday use due to bandwidth limitations, high costs, and technical complexity. Students learned about it as science fiction technology that might work in research labs but would never be accessible to ordinary people. Textbooks described video calling as requiring expensive, specialized equipment and dedicated high-speed connections that would make it impractical for homes or small businesses.

What we know now:

Technology classes taught that video calling was an interesting novelty but would never be practical due to bandwidth limitations, cost, and technical complexity. Students learned about it as science fiction rather than near-future technology. Video calling became commonplace through services like Skype, FaceTime, Zoom, and WhatsApp. The COVID-19 pandemic made video conferencing essential for work, education, and social connection. Improvements in internet speed, compression technology, and device capabilities made high-quality video calling accessible and affordable worldwide.
  • Astronomy & Space
2006

There Are Nine Planets in Our Solar System

What you learned in school:

Astronomy textbooks definitively listed nine planets in our solar system, with Pluto as the smallest and most distant. Students memorized the order using mnemonics like "My Very Educated Mother Just Served Us Nine Pizzas." Pluto's planetary status was taught as scientific fact for over 75 years.

What we know now:

Every astronomy textbook and classroom poster listed nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Students memorized mnemonics like "My Very Educated Mother Just Served Us Nine Pizzas." Pluto was discovered in 1930 and immediately classified as the ninth planet. In 2006, the International Astronomical Union reclassified Pluto as a "dwarf planet" due to its small size and failure to clear its orbital neighborhood. This decision was controversial but based on more precise definitions of what constitutes a planet.
  • Biology & Medicine
2000

Humans Descended Directly from Neanderthals

What you learned in school:

Anthropology textbooks taught that modern humans evolved directly from Neanderthals in a linear evolutionary progression. Students learned about the "missing link" and saw diagrams showing ape to Neanderthal to modern human in a straight line. This "Neanderthal phase" in human evolution was presented as an established fact, with Neanderthals depicted as our direct ancestors rather than cousins.

What we know now:

Anthropology textbooks taught that modern humans evolved directly from Neanderthals in a linear progression. Students learned about the "missing link" and saw diagrams showing ape to Neanderthal to modern human. Neanderthals were depicted as our direct ancestors. Genetic analysis has revealed that modern humans and Neanderthals are separate species that evolved from a common ancestor. However, humans and Neanderthals did interbreed, and most non-African humans carry 1-2% Neanderthal DNA. The relationship is more complex than the simple linear evolution once taught.
  • Biology & Medicine
2000

The Appendix Has No Function

What you learned in school:

Medical textbooks described the appendix as a classic "vestigial organ" - a useless evolutionary leftover from herbivorous ancestors who needed help digesting plant matter. Students learned it was like the tailbone, a remnant with no current purpose whose only significance was causing appendicitis. Medical schools taught that it was an evolutionary relic that served no function in modern humans and could be safely removed without consequence.

What we know now:

Medical textbooks described the appendix as a vestigial organ - a useless evolutionary leftover from our herbivorous ancestors. Students learned it was like the tailbone, a remnant with no current purpose. The only time it was mentioned was in the context of appendicitis. Research has now shown that the appendix serves as a reservoir for beneficial gut bacteria. It helps recolonize the intestines with good bacteria after illness or antibiotic treatment. It's part of the immune system and may play a role in developing immune responses. The "useless organ" narrative has been completely overturned.
  • Physics & Chemistry
2000

Absolute Zero Is Impossible to Reach

What you learned in school:

Physics textbooks taught that absolute zero (-273.15°C or 0 Kelvin) was a theoretical limit that could never actually be reached in practice. Students learned that the third law of thermodynamics made it fundamentally impossible to cool any system to absolute zero temperature. This was presented as an unbreakable physical law, with textbooks emphasizing that while scientists could approach absolute zero, they could never actually achieve it due to quantum mechanical limitations.

What we know now:

Physics classes taught that absolute zero (-273.15°C or 0 Kelvin) was the theoretical lowest possible temperature that could never actually be achieved. Students learned about the third law of thermodynamics and the impossibility of reaching this limit. Scientists have created temperatures below absolute zero in laboratory conditions using quantum mechanical systems. These "negative temperature" systems are actually hotter than any positive temperature and represent exotic quantum states. While still extremely difficult to achieve, absolute zero is no longer considered absolutely impossible.
  • Nutrition & Health
2000

All Fats Are Bad for You

What you learned in school:

Nutrition education taught that all dietary fats were harmful and should be minimized or eliminated from the diet. Students learned that fat made you fat and caused heart disease, with no distinction between different types of fats. The food pyramid emphasized carbohydrates and portrayed all fats equally as dangerous. Health classes taught that low-fat and fat-free products were always healthier choices, leading to the promotion of high-carbohydrate, processed foods as superior alternatives.

What we know now:

Nutrition education taught that all dietary fats were harmful and should be minimized. Students learned that fat made you fat and caused heart disease. The food pyramid emphasized carbohydrates and minimized all fats equally. Nutritional science now distinguishes between different types of fats. Monounsaturated and polyunsaturated fats (found in olive oil, nuts, fish) are beneficial for health. Even some saturated fats may not be as harmful as once thought. Trans fats are the most harmful. The body needs essential fatty acids for brain function, hormone production, and nutrient absorption. The "all fat is bad" message led to increased consumption of refined carbohydrates.
  • Nutrition & Health
2000

Salt Is Bad for Everyone

What you learned in school:

Health education classes taught that everyone should minimize salt intake to prevent high blood pressure and heart disease. Students learned that salt was universally harmful and that low-sodium diets were always healthier for all people. Textbooks presented a simple "salt is bad" message without discussing individual variations in salt sensitivity. The recommendation was for everyone to drastically reduce sodium consumption regardless of their personal health profile or blood pressure status.

What we know now:

Health education taught that everyone should minimize salt intake to prevent high blood pressure and heart disease. Students learned that salt was universally harmful and that low-sodium diets were always better. Only about 25% of people are "salt-sensitive" and experience significant blood pressure changes from sodium intake. For most people, moderate salt consumption doesn't pose health risks. Very low-sodium diets can actually be harmful for some individuals. The relationship between salt and health is more complex than the simple "salt is bad" message suggested. Individual responses to sodium vary greatly.
  • Technology & Computing
2000

The Internet Is Just a Fad

What you learned in school:

Technology and business classes in the early 1990s often dismissed the internet as a temporary novelty with limited practical applications. Students learned about it as an academic curiosity mainly useful for researchers and computer enthusiasts. Many textbooks and instructors taught that the internet lacked the infrastructure for serious commerce, was too difficult for average users, and would never replace traditional methods of communication, shopping, or information access. The prevailing view was that it was just another technological fad that would fade away.

What we know now:

Technology and business classes often dismissed the early internet as a temporary novelty with limited practical applications. Students learned about it as a curiosity mainly useful for academics and researchers. The internet became essential global infrastructure supporting commerce, communication, entertainment, education, and virtually every aspect of modern life. It transformed entire industries and created new forms of social interaction, business models, and economic activity. The prediction failed to recognize the internet's potential for revolutionizing information sharing and global connectivity.
  • Technology & Computing
2000

Robots Will Replace All Human Workers by 2000

What you learned in school:

Technology and business education classes in the 1970s and 1980s predicted that automation and robotics would eliminate most human jobs by the year 2000. Students learned about a future where robots would handle manufacturing, service work, and even white-collar tasks, leaving humans with abundant leisure time. Textbooks described this as an inevitable technological progression, with some educators suggesting that society would need to restructure around a "post-work" economy supported entirely by robotic labor.

What we know now:

Technology and social studies classes predicted that automation and robotics would eliminate most human jobs by the year 2000. Students learned about a future of leisure supported by robot labor. While automation has eliminated some jobs and transformed others, it has also created new types of employment. Humans and robots often work together rather than robots simply replacing humans. Many jobs require human creativity, empathy, and complex problem-solving that robots cannot provide. The transition has been more gradual and selective than the complete replacement scenario predicted.
  • Technology & Computing
2000

Flying Cars Will Be Common by 2000

What you learned in school:

Technology and futurism classes in the 1970s and 1980s predicted that personal flying vehicles would be commonplace by the year 2000. Students learned about a future of three-dimensional transportation where families would commute by air. Textbooks showed illustrations of flying cars as the inevitable next step in transportation evolution. The predictions assumed that technological advances would quickly solve the engineering challenges of personal flight, making aerial commuting as common as driving.

What we know now:

Technology and futurism classes predicted that personal flying vehicles would be commonplace by the turn of the century. Students learned about a future of three-dimensional transportation and aerial commuting. Flying cars remain extremely rare due to technical challenges (energy requirements, safety, noise], regulatory hurdles (air traffic control, licensing], and practical issues (cost, infrastructure, weather dependence). While prototypes exist, the vision of widespread personal flying vehicles has not materialized as predicted. Ground transportation has proven more practical and efficient for most applications.
  • Environmental Science
2000

Global Warming Will Take Centuries to Show Effects

What you learned in school:

Early environmental science classes in the 1970s and 1980s taught that global warming would be a gradual process taking centuries or millennia to produce noticeable effects. Students learned that climate change was a distant future concern that would primarily affect their great-great-grandchildren. Textbooks presented climate change as a slow, linear process where effects would accumulate over geological timescales, making it seem like a theoretical problem rather than an immediate concern requiring urgent action.

What we know now:

Early environmental science classes taught that global warming would be a gradual process taking centuries to produce noticeable effects. Students learned about climate change as a distant future problem for their great-grandchildren. Climate change effects have become apparent much faster than initially predicted. Arctic ice loss, sea level rise, extreme weather events, and ecosystem shifts are occurring within decades rather than centuries. Feedback loops and tipping points have accelerated some changes. The pace of climate change has outstripped many early predictions, requiring more urgent action than originally anticipated.
  • Biology & Medicine
1990

Stomach Ulcers Are Caused by Stress and Spicy Food

What you learned in school:

Medical textbooks taught that stomach ulcers were caused by stress, anxiety, and spicy foods. Students learned that "Type A" personalities and those who consumed hot peppers and acidic foods were at highest risk. Treatment focused on bland diets, stress management, and avoiding "trigger foods" like coffee and spicy cuisine.

What we know now:

For decades, medical textbooks taught that stomach ulcers were primarily caused by stress, spicy food, and excess stomach acid. Students learned that Type A personalities and those who ate hot, spicy foods were at highest risk. The treatment focused on bland diets, stress reduction, and antacids. This theory was completely overturned when Barry Marshall and Robin Warren discovered that most ulcers are actually caused by Helicobacter pylori bacteria. Marshall even infected himself with H. pylori to prove the connection, later winning a Nobel Prize for this discovery.
  • Biology & Medicine
1990

Humans Only Use 10% of Their Brain

What you learned in school:

Psychology and biology textbooks taught that humans use only 10% of their brain capacity. Students learned that if they could unlock the remaining 90%, they could achieve superhuman abilities. This "fact" was often attributed to William James or Albert Einstein and became popular through Dale Carnegie's self-help books.

What we know now:

This persistent myth was taught in psychology and biology classes for generations. Students were told that if they could unlock the other 90% of their brain, they could achieve superhuman abilities. The claim was often attributed to William James or Albert Einstein. Modern brain imaging technology like PET scans and fMRI have shown that we use virtually all of our brain, even during simple tasks. Even during sleep, many areas of the brain are active. Brain damage to any area typically causes noticeable deficits, proving every part has function.
  • Biology & Medicine
1990

Blood Is Blue Until It Hits Oxygen

What you learned in school:

Biology textbooks taught that deoxygenated blood in veins was blue until it contacted oxygen and turned red. Students learned to identify "blue blood" in diagrams showing the circulatory system. This explained why veins appear blue through the skin, and medical textbooks included illustrations of blue veins versus red arteries.

What we know now:

Students were taught that deoxygenated blood in veins is blue, and only turns red when exposed to oxygen. This explained why veins appear blue through the skin. Textbooks often included diagrams showing blue veins and red arteries. In reality, blood is always red - it's just darker when deoxygenated. Veins appear blue due to the way light penetrates skin and is absorbed and reflected. Blue light penetrates deeper than red light, making the veins appear blue to our eyes. This is purely an optical phenomenon.
  • Biology & Medicine
1990

The Tongue Has Different Taste Zones

What you learned in school:

Biology textbooks taught that different areas of the tongue were exclusively responsible for detecting specific tastes: sweet at the tip, bitter at the back, sour on the sides, and salty near the tip sides. Students memorized these "taste zones" from colorful diagrams and performed lab experiments placing taste strips on different tongue areas. This "taste map" was presented as established anatomical fact and became a popular classroom demonstration for decades.

What we know now:

Biology classes taught that different areas of the tongue were responsible for detecting different tastes: sweet at the tip, bitter at the back, sour on the sides, and salty on the sides near the tip. Students memorized these zones and drew diagrams. This "taste map" was based on a mistranslation of German research from 1901. In reality, taste buds for all flavors are distributed across the entire tongue, though some areas may be slightly more sensitive to certain tastes. The misconception persisted for nearly a century in textbooks.
  • Biology & Medicine
1990

You Cannot Grow New Brain Cells After Childhood

What you learned in school:

Neuroscience textbooks taught that humans were born with all the brain cells they would ever have. After early childhood development, the brain was considered "fixed" and incapable of generating new neurons. Students learned that brain damage was permanent because dead neurons could never be replaced. This fundamental principle was taught as established fact in medical schools and shaped decades of neuroscience education.

What we know now:

Neuroscience textbooks taught that humans are born with all the brain cells they'll ever have. After childhood brain development, no new neurons could be generated. Students learned that brain damage was permanent because dead neurons couldn't be replaced. This was considered an established fact about the adult brain. Research beginning in the 1990s discovered neurogenesis - the birth of new neurons - continues throughout adult life, particularly in the hippocampus. Exercise, learning, and environmental enrichment can promote new neuron growth. This discovery revolutionized understanding of brain plasticity and recovery.
  • Astronomy & Space
1990

Black Holes Destroy Everything That Enters Them

What you learned in school:

Astronomy textbooks taught that black holes were cosmic vacuum cleaners that completely destroyed all matter and information crossing their event horizons. Students learned that nothing could ever escape and everything was crushed to infinite density at the singularity. Black holes were portrayed as ultimate destructive forces that annihilated anything unfortunate enough to fall into them.

What we know now:

Astronomy textbooks taught that black holes were cosmic vacuum cleaners that destroyed all matter and information that crossed their event horizons. Nothing could ever escape, and everything was crushed to infinite density. Stephen Hawking's work showed that black holes actually emit radiation (Hawking radiation) and slowly evaporate over time. They also don't destroy information - it may be encoded on the event horizon. Black holes are more complex objects that follow quantum mechanical principles, not just simple destructive forces.
  • Geography & Geology
1990

The Grand Canyon Formed Gradually Over Millions of Years

What you learned in school:

Geography textbooks taught that the Grand Canyon formed through slow, uniform erosion over millions of years as a classic example of gradual geological processes. Students learned about the steady, consistent work of the Colorado River cutting through rock layers at a constant rate. This was presented as the definitive model of how major geological features form through imperceptibly slow changes over vast time periods. The uniformitarian principle suggested that current processes operating at current rates could explain all geological formations.

What we know now:

Geography textbooks taught that the Grand Canyon formed through slow, uniform erosion over millions of years - a classic example of gradual geological processes. Students learned about the steady work of the Colorado River cutting through rock layers. While long-term erosion is still important, evidence suggests the canyon's formation involved more rapid processes including catastrophic flooding, rapid downcutting during specific geological periods, and complex interactions between different erosional processes. The formation was more episodic and dramatic than the simple gradual erosion model suggested.
  • Physics & Chemistry
1990

Glass Is a Very Slow-Moving Liquid

What you learned in school:

Chemistry and physics textbooks taught that glass was actually a liquid that flows extremely slowly over time. Students learned that old cathedral windows were thicker at the bottom because the glass had "flowed" downward over centuries. This seemed to explain the uneven thickness of antique glass panes and was presented as evidence of glass being liquid.

What we know now:

Chemistry and physics classes often taught that glass is actually a liquid that flows very slowly over time. Students learned that old windows are thicker at the bottom because the glass has flowed downward over centuries. This explained why antique glass panes seem uneven. Glass is actually an amorphous solid - it has a rigid structure but lacks the crystalline organization of typical solids. The thickness variations in old windows result from manufacturing processes, not flow. Glass doesn't flow at room temperature; it would take longer than the age of the universe to see any measurable flow.
  • Psychology & Social Sciences
1990

Multiple Personality Disorder Is Common

What you learned in school:

Psychology textbooks presented multiple personality disorder as a fascinating and relatively common mental health condition. Students learned about dramatic cases with dozens of distinct personalities, often through famous case studies like "The Three Faces of Eve" and "Sybil." The condition was portrayed as a clear example of how trauma could fragment the mind into separate identities.

What we know now:

Psychology textbooks featured multiple personality disorder (now called dissociative identity disorder) as a relatively common condition. Popular media like "The Three Faces of Eve" and "Sybil" reinforced this perception. Students learned about dramatic cases of people with many distinct personalities. Dissociative identity disorder is extremely rare, and many of the famous cases that made it seem common were later found to be inaccurate or potentially iatrogenic (caused by therapy itself). The condition became overdiagnosed in the 1980s and 1990s, leading to more careful diagnostic criteria and recognition of how suggestion and expectation can influence patient presentations.
  • Psychology & Social Sciences
1990

Repressed Memories Can Be Reliably Recovered

What you learned in school:

Psychology courses taught that traumatic memories could be completely repressed and then accurately recovered through specialized therapy techniques like hypnosis and guided imagery. Students learned that psychological problems often stemmed from hidden childhood trauma that could be unlocked through proper therapeutic methods.

What we know now:

Psychology courses taught that traumatic memories could be completely repressed and then accurately recovered through therapy techniques like hypnosis or guided imagery. The "recovered memory" movement suggested that many psychological problems stemmed from repressed childhood trauma. Memory research has shown that memory is reconstructive and highly suggestible. "Recovered" memories are often false memories created by suggestion during therapy. While trauma can affect memory, the specific idea of complete repression followed by accurate recovery has been largely debunked. Many "recovered memory" cases led to false accusations and family destruction.
  • Nutrition & Health
1990

Margarine Is Healthier Than Butter

What you learned in school:

Health and nutrition classes taught that margarine was a healthier alternative to butter because it was lower in saturated fat and cholesterol-free. Students learned that artificial fats were scientifically superior to natural animal fats. Textbooks promoted margarine as a heart-healthy choice without mentioning the hydrogenation process or trans fats. The message was that modern food science had created a better, safer alternative to traditional butter through industrial processing.

What we know now:

Health and nutrition classes taught that margarine was a healthier alternative to butter because it was lower in saturated fat and cholesterol. Students learned that artificial fats were better than natural animal fats. Many margarines contained trans fats, which are now known to be more harmful than the saturated fats in butter. Trans fats raise bad cholesterol and lower good cholesterol, increasing heart disease risk. The hydrogenation process that made margarine solid created these harmful trans fats. Butter, while high in saturated fat, is now considered less harmful than margarine containing trans fats.
  • Nutrition & Health
1990

Cracking Knuckles Causes Arthritis

What you learned in school:

Health classes taught that the habit of cracking knuckles would lead to arthritis and joint problems later in life. Students were warned against this behavior to protect their long-term joint health and prevent future disability. Teachers often told students that the cracking sound indicated damage to bones or cartilage. The message was that this seemingly harmless habit would cause serious consequences including swollen, painful joints and reduced mobility in adulthood.

What we know now:

Health classes taught that the habit of cracking knuckles would lead to arthritis and joint problems later in life. Students were warned against this behavior to protect their long-term joint health. Multiple studies have found no causal relationship between knuckle cracking and arthritis. The sound comes from gas bubbles collapsing in joint fluid, not from damage to bones or cartilage. Long-term studies of habitual knuckle crackers show no increased rates of arthritis compared to non-crackers. While excessive force could potentially cause injury, normal knuckle cracking appears harmless.
  • Technology & Computing
1990

No One Will Ever Need More Than 640K of RAM

What you learned in school:

Computer classes taught that 640 kilobytes of memory was more than sufficient for any conceivable computer application. Students learned about memory as a precious, limited resource that would always need to be carefully managed and conserved. Textbooks emphasized efficient programming to work within these memory constraints. The assumption was that software would remain relatively simple and that 640K represented a generous amount of memory that would satisfy computing needs indefinitely.

What we know now:

Computer classes taught that 640 kilobytes of memory was more than sufficient for any conceivable computer application. Students learned about memory as a precious, limited resource that would always be carefully managed. Modern computers routinely use gigabytes (thousands of times more) of RAM, and even smartphones have multiple gigabytes of memory. Software applications, operating systems, and multimedia content have grown to take advantage of increased memory availability. The prediction failed to anticipate the exponential growth in software complexity and the decreasing cost of memory components.
  • Environmental Science
1990

The Ozone Hole Is Directly Above Antarctica Only

What you learned in school:

Environmental science textbooks initially described the ozone hole as a localized phenomenon affecting only Antarctica, far from populated areas. Students learned about it as a remote problem with little relevance to their daily lives or global health. The focus was on the Antarctic ozone depletion as an isolated scientific curiosity rather than a worldwide environmental threat. Textbooks presented it as a regional atmospheric anomaly that would remain confined to the polar region.

What we know now:

Environmental science textbooks initially described the ozone hole as a localized phenomenon affecting only Antarctica. Students learned about it as a remote problem with little global impact. While the largest ozone depletion occurs over Antarctica, ozone thinning affects the entire globe. UV radiation increases worldwide due to overall ozone reduction. The Antarctic ozone hole influences global atmospheric circulation and weather patterns. Ozone-depleting chemicals spread throughout the atmosphere, affecting ozone layers everywhere. The problem had global implications for human health and ecosystems, not just Antarctic effects.
  • Environmental Science
1990

Plastic Will Solve All Packaging Problems

What you learned in school:

Science and technology classes in the 1950s and 1960s promoted plastic as the miracle material that would solve all packaging problems. Students learned that plastic was lightweight, durable, waterproof, and infinitely versatile - the perfect replacement for glass, paper, and metal containers. Textbooks described plastic as a technological triumph that would improve quality of life while being economical and practical. The environmental impact was not discussed, as plastic was seen as purely beneficial with no downsides.

What we know now:

Science and technology classes taught that plastic was the perfect packaging material - lightweight, durable, waterproof, and versatile. Students learned about plastic as a technological triumph that would improve life quality. Plastic pollution has created massive environmental problems including ocean garbage patches, microplastics in food chains, and persistent waste that takes centuries to decompose. Plastic production contributes to climate change, and plastic additives can be toxic. While plastic has benefits, the environmental costs were not anticipated when it was promoted as a universal solution to packaging needs.
  • Environmental Science
1990

Landfills Are Safe for Groundwater

What you learned in school:

Environmental science classes taught that properly designed landfills with clay liners and collection systems would safely contain waste without affecting groundwater supplies. Students learned about multiple barrier systems that would prevent any contamination from reaching drinking water sources. Textbooks presented landfills as engineered solutions that could permanently isolate waste from the environment. The long-term effectiveness of containment systems was presented as proven and reliable technology.

What we know now:

Environmental science classes taught that properly designed landfills would safely contain waste without affecting groundwater supplies. Students learned about clay liners and other barriers that would prevent contamination. Many landfills, even those designed with barriers, have contaminated groundwater with toxic chemicals, heavy metals, and other pollutants. Liner systems can fail over time, and some older landfills had no protective barriers. Groundwater contamination from landfills has affected drinking water supplies and required expensive cleanup efforts. The long-term effectiveness of containment systems was overestimated.
  • Environmental Science
1990

Industrial Agriculture Is Completely Sustainable

What you learned in school:

Agricultural science classes taught that modern industrial farming methods using synthetic fertilizers and pesticides were completely sustainable and could feed the world indefinitely. Students learned about the Green Revolution as an unqualified success that solved world hunger. Textbooks presented industrial agriculture as scientifically superior to traditional farming methods, emphasizing increased yields and efficiency. The focus was on technological solutions to food production with no discussion of environmental costs or long-term sustainability concerns.

What we know now:

Agricultural science classes taught that modern industrial farming methods using synthetic fertilizers and pesticides were sustainable and could feed the world indefinitely. Students learned about the Green Revolution as an unqualified success. Industrial agriculture has led to soil depletion, water pollution, loss of biodiversity, and resistance to pesticides. Monoculture farming has made crops more vulnerable to pests and diseases. The external costs of industrial agriculture include environmental damage and health effects that were not considered in the original sustainability assessments. More sustainable approaches are needed for long-term food security.
  • Environmental Science
1986

Nuclear Power Is 100% Safe

What you learned in school:

Science classes taught that nuclear power was completely safe due to multiple redundant safety systems and careful engineering design. Students learned about nuclear energy as a clean, risk-free alternative to fossil fuels with no possibility of accidents. Textbooks emphasized the multiple safety barriers and automatic shutdown systems that made nuclear plants foolproof. The technology was presented as having eliminated all risks through advanced engineering and strict safety protocols.

What we know now:

Science classes taught that nuclear power was completely safe due to multiple safety systems and careful engineering. Students learned about nuclear energy as clean and risk-free compared to fossil fuels. The Chernobyl disaster (1986) and Fukushima disaster (2011) demonstrated that nuclear accidents can have catastrophic consequences. While nuclear power has an overall good safety record, these accidents showed that human error, design flaws, and natural disasters can overcome safety systems. Nuclear waste disposal also remains a long-term challenge. Nuclear power has benefits but is not risk-free as once taught.
  • Biology & Medicine
1980

There Are Only Four Basic Tastes

What you learned in school:

Biology textbooks taught that the human tongue could detect exactly four basic tastes: sweet, sour, salty, and bitter. Students memorized this as established scientific fact and learned to identify these taste regions on tongue diagrams. Science classes presented this four-taste system as complete and comprehensive.

What we know now:

Biology textbooks consistently taught that humans could only detect four basic tastes: sweet, sour, salty, and bitter. Taste maps showed different areas of the tongue responsible for each taste. This was considered scientific fact and was taught alongside the anatomy of taste buds. In the 1980s, umami (savory/meaty) was recognized as the fifth basic taste, particularly through the work of Japanese scientist Kikunae Ikeda who identified glutamate receptors. The taste map of the tongue was also debunked - all tastes can be detected across the entire tongue.
  • Biology & Medicine
1980

Tonsils Are Useless and Should Be Removed Preventively

What you learned in school:

Medical textbooks described tonsils as vestigial organs with no important function - evolutionary leftovers that served no purpose in modern humans. Students learned that tonsils were "portals of infection" that should be removed preventively to avoid future illness. Tonsillectomy was routine surgery performed on millions of children annually, often combined with adenoid removal. The procedure peaked in the 1950s when it was considered standard preventive care.

What we know now:

For much of the 20th century, tonsils were considered vestigial organs with no important function. Many children had their tonsils removed preventively to avoid future infections. It was routine surgery, often done along with adenoid removal. Medical schools taught that tonsils were evolutionary leftovers. We now know that tonsils are important parts of the immune system, particularly in childhood. They help develop immune responses and contain infection-fighting cells. Preventive removal is no longer recommended except in specific medical circumstances.
  • Astronomy & Space
1980

The Moon Was Formed from Earth's Material

What you learned in school:

Astronomy textbooks taught that the Moon formed alongside Earth from the same primordial material during the solar system's creation. Students learned about the "sister planet" theory of lunar formation, where both bodies condensed from the same cosmic dust and gas. This seemed logical given their proximity and was the accepted explanation for decades before Apollo moon rocks were analyzed.

What we know now:

Astronomy classes taught that the Moon formed from the same material as Earth during the solar system's formation, or that it was captured by Earth's gravity. Students learned about the "sister planet" theory of lunar formation. Analysis of Moon rocks brought back by Apollo missions showed significant differences in composition between Earth and Moon materials. The current leading theory is the Giant Impact Hypothesis - that a Mars-sized object collided with early Earth, and the debris from this collision eventually formed the Moon. This explains both the similarities and differences in composition.
  • Astronomy & Space
1980

Space Is Completely Empty

What you learned in school:

Physics textbooks described space as a perfect vacuum - absolutely empty between celestial objects. Students learned that space was pure nothingness punctuated only by stars and planets. This "empty space" concept was fundamental to understanding astronomy and physics, with space portrayed as a vast void through which objects moved.

What we know now:

Physics textbooks described space as a perfect vacuum - completely empty between celestial objects. Students learned that space was just emptiness with occasional planets and stars. This "empty space" concept was fundamental to understanding the cosmos. Modern astronomy has discovered that space is filled with dark matter, dark energy, cosmic rays, interstellar gas and dust, magnetic fields, and various subatomic particles. What we once thought was empty is actually a complex medium that plays crucial roles in cosmic evolution and structure formation.
  • Geography & Geology
1980

Antarctica Is Just a Frozen Wasteland

What you learned in school:

Geography textbooks described Antarctica as a lifeless, uniform ice sheet with no biological activity or interesting geological features. Students learned about it as Earth's most barren and desolate continent, covered entirely in featureless ice and snow. The focus was on its extreme cold and isolation, with no mention of ecosystems, wildlife, or geological diversity. Antarctica was presented as a frozen wasteland with nothing of scientific interest beyond its role as the coldest place on Earth.

What we know now:

Geography classes described Antarctica as a lifeless, uniform ice sheet with no interesting features or ecosystems. Students learned about it as Earth's most barren continent with nothing but ice and snow. Scientific exploration has revealed Antarctica's rich geology, unique ecosystems, underground lakes, ice-free valleys, active volcanoes, and diverse wildlife. The continent has complex weather patterns, varied landscapes, and plays crucial roles in global climate and ocean circulation. It's far from the uniform wasteland once depicted in textbooks.
  • Geography & Geology
1980

All Deserts Are Hot

What you learned in school:

Geography textbooks typically defined deserts by their hot, sandy characteristics like the Sahara. Students learned about camels, cacti, and scorching heat as the defining features of all deserts. The focus was almost entirely on hot, arid environments with sand dunes and extreme temperatures. Cold environments like Antarctica or the winter conditions of the Gobi Desert were not classified as deserts, leading students to associate deserts exclusively with hot climates and sandy landscapes.

What we know now:

Geography textbooks typically defined deserts by their hot, sandy characteristics. Students learned about camels, cacti, and scorching heat as defining desert features. The focus was almost entirely on hot deserts like the Sahara. Cold deserts like Antarctica, the Gobi Desert's winter conditions, and high-altitude deserts were often overlooked or misclassified. A desert is actually defined by low precipitation, not temperature. Antarctica is technically Earth's largest desert, receiving less precipitation than the Sahara despite being covered in ice.
  • Geography & Geology
1980

Rivers Always Flow North to South

What you learned in school:

Elementary geography classes often taught or implied that rivers naturally flow from north to south, possibly influenced by the typical orientation of maps with north at the top. Students developed the misconception that "down" on a map corresponded to water flow direction. Teachers sometimes used phrases like "rivers flow downhill" without clarifying that this meant following gravity and topography, not compass directions. The concept that rivers could flow north was rarely discussed or seemed counterintuitive to students.

What we know now:

Elementary geography often taught or implied that rivers naturally flow from north to south, possibly due to the way maps are typically oriented. Students sometimes developed the misconception that "down" on a map meant water flow direction. Rivers actually flow downhill following gravity and topography, regardless of compass direction. The Nile flows north, many Russian rivers flow north to the Arctic Ocean, and rivers flow in all directions depending on the local landscape. Elevation, not cardinal direction, determines river flow.
  • Physics & Chemistry
1980

There Are Four Fundamental Forces

What you learned in school:

Physics textbooks taught that there were exactly four fundamental forces in nature: gravity, electromagnetism, strong nuclear force, and weak nuclear force. Students memorized these as the complete and final set of forces that explained all interactions in the universe. This "complete" list was presented as established fact.

What we know now:

Physics textbooks taught four fundamental forces: gravity, electromagnetism, strong nuclear, and weak nuclear forces. Students memorized these as the complete set of forces in nature. Modern physics has shown that the electromagnetic and weak nuclear forces are actually aspects of a single electroweak force at high energies. Grand unified theories suggest that strong, weak, and electromagnetic forces may unify at even higher energies. String theory and other approaches propose that all forces, including gravity, may be manifestations of a single underlying force or principle.
  • Physics & Chemistry
1980

Sound Cannot Travel Through Space

What you learned in school:

Physics classes taught that sound waves require a medium like air or water to travel, and therefore sound cannot exist in the vacuum of space. Students learned that space is completely silent because there are no molecules to carry sound waves. Textbooks emphasized that astronauts could not hear explosions or other sounds in space due to the absence of air. This was presented as an absolute physical law with no exceptions or alternative forms of acoustic phenomena in space environments.

What we know now:

Physics classes taught that sound waves require a medium like air or water to travel, and therefore cannot exist in the vacuum of space. Students learned that space is silent because sound needs matter to propagate. While traditional sound waves cannot travel through vacuum, space isn't completely empty. Electromagnetic waves can carry acoustic information, and plasma waves in space can behave similarly to sound. Additionally, spacecraft and space stations contain air where sound travels normally. The principle is correct for traditional acoustic waves, but space-based "sounds" do exist in other forms.
  • History
1980

The Great Wall of China Is Visible from Space

What you learned in school:

Geography and history classes taught that the Great Wall of China was the only human-made structure visible from space with the naked eye. This was presented as a testament to the wall's immense scale and one of humanity's greatest architectural achievements. Students learned this as an amazing fact that demonstrated the wall's extraordinary size and importance. Textbooks often included this claim as evidence of the wall's status as one of the wonders of the world, emphasizing its visibility from orbit as proof of its magnificence.

What we know now:

Geography and history classes taught that the Great Wall of China was the only human-made structure visible from space with the naked eye. This was presented as a testament to the wall's immense scale and one of humanity's greatest achievements. Astronauts have confirmed that the Great Wall is not visible to the naked eye from space. Many other human structures like cities, highways, and large buildings are more easily seen from orbit. The wall is narrow and made of materials that blend with the surrounding landscape. This myth likely originated from the wall's impressive length being confused with visibility from great distances.
  • History
1980

Cowboys Were Mostly White

What you learned in school:

Western history textbooks and popular culture depicted cowboys as almost exclusively white American men. Students learned about rugged individualists conquering the frontier, with textbooks rarely mentioning Mexican vaqueros, Black cowboys, or Native American cattle workers. Hollywood westerns reinforced this whites-only image of the American cowboy.

What we know now:

Western history and popular culture depicted cowboys as almost exclusively white men, reinforcing stereotypes about the American frontier. Textbooks and media rarely mentioned the diversity of cattle workers. Historical records show that about 25% of cowboys were Black, many were Mexican vaqueros, and Native Americans also worked cattle. The mythologized "cowboy" of popular culture erased the significant contributions of people of color to the cattle industry. The real American West was far more diverse than Hollywood westerns suggested.
  • Psychology & Social Sciences
1980

IQ Tests Measure Pure Intelligence

What you learned in school:

Educational psychology textbooks taught that IQ tests provided objective, culture-free measurements of innate intellectual capacity. Students were taught that IQ scores reflected their true, fixed intelligence regardless of background, education, or circumstances. Schools used IQ tests to permanently track students into different academic levels based on these "objective" intelligence measures.

What we know now:

Educational psychology taught that IQ tests provided objective, unbiased measurements of innate intelligence. Students were taught that IQ scores reflected their true intellectual capacity regardless of background. IQ tests contain significant cultural and educational biases that favor certain backgrounds and experiences. They measure specific types of reasoning that are valued in particular cultures and educational systems, not universal intelligence. Factors like socioeconomic status, language background, test anxiety, and cultural familiarity with testing formats all affect scores. Intelligence is also more complex and multifaceted than any single test can measure.
  • Psychology & Social Sciences
1980

Children Are Blank Slates

What you learned in school:

Developmental psychology textbooks taught that children are born as "blank slates" (tabula rasa) with no innate characteristics, abilities, or predispositions. Students learned that all personality traits, intelligence, and behavior patterns came entirely from environmental influences and learning experiences. This theory, popularized by John Locke, was presented as scientific fact in psychology courses, with the nature versus nurture debate heavily weighted toward nurture as the sole determining factor in human development.

What we know now:

Developmental psychology taught that children are born as "blank slates" (tabula rasa) and that all behavior, personality, and abilities come from environmental influences and learning. Nature versus nurture was seen as entirely nurture. Modern research shows that children are born with innate predispositions, temperaments, and genetic influences that interact with environmental factors. Twin studies and adoption studies demonstrate significant genetic components to personality, intelligence, and behavior. Development results from complex interactions between genetic predispositions and environmental influences, not just environmental shaping of blank slates.
  • Psychology & Social Sciences
1980

Autism Is Caused by Cold Mothers

What you learned in school:

Psychology textbooks taught that autism was caused by emotionally distant "refrigerator mothers" who failed to provide proper maternal warmth and bonding. Students learned that cold, rejecting mothers created autistic children through poor parenting. This theory blamed mothers for their children's autism and suggested that warmer, more attentive parenting could prevent or cure the condition.

What we know now:

Psychology textbooks taught that autism was caused by emotionally distant "refrigerator mothers" who failed to bond properly with their children. Students learned about poor parenting as the root cause of autistic behaviors. Autism is a neurodevelopmental condition with strong genetic components and differences in brain structure and function. The "refrigerator mother" theory was based on poor research methodology and caused tremendous guilt and blame for parents. Modern research focuses on genetic factors, prenatal development, and neurological differences rather than parenting styles. The theory has been completely discredited.
  • Psychology & Social Sciences
1980

Mental Illness Is a Sign of Moral Weakness

What you learned in school:

Psychology and health classes taught that mental illness resulted from character defects, lack of willpower, or moral failings. Students learned that depression meant weakness, that anxiety showed lack of faith or courage, and that people could overcome mental problems through positive thinking and self-discipline. Mental illness was seen as a personal failing rather than a medical condition.

What we know now:

Psychology and health classes often taught or implied that mental illness resulted from character flaws, weak willpower, or moral failings. Students learned that people could "snap out of" depression or anxiety through effort and positive thinking. Mental illnesses are medical conditions involving brain chemistry, genetics, and neurological factors. They are not character flaws or choices. Chemical imbalances, genetic predispositions, trauma, and biological factors all contribute to mental health conditions. Treatment requires medical and psychological intervention, not just willpower. The stigma of moral weakness has prevented many people from seeking needed help.
  • Psychology & Social Sciences
1980

Lie Detectors Are Reliable

What you learned in school:

Criminal justice and psychology classes taught that polygraph machines were scientific instruments that could accurately detect lies by measuring physiological responses. Students learned that lie detectors were nearly foolproof tools used by law enforcement and that passing or failing a polygraph test was strong evidence of truthfulness or deception.

What we know now:

Criminal justice and psychology classes taught that polygraph machines could accurately detect lies by measuring physiological responses. Students learned that lie detectors were scientific instruments that could determine truth from deception. Polygraphs measure stress responses, not lies specifically. They can be fooled by people who remain calm while lying or triggered by people who are nervous but truthful. They have high rates of false positives and false negatives. Most courts don't accept polygraph evidence because of reliability issues. The machines detect arousal and stress, which can have many causes besides deception.
  • Nutrition & Health
1980

Spinach Is Extremely High in Iron

What you learned in school:

Nutrition textbooks listed spinach as one of the highest iron-content foods available, making it a superfood for preventing anemia. Students learned that Popeye's incredible strength from eating spinach was based on its exceptional iron content. Health classes taught that spinach was the best dietary source of iron, especially important for growing children and people with anemia. The nutritional charts showed spinach with remarkably high iron levels compared to other vegetables and even some meats.

What we know now:

Nutrition textbooks listed spinach as one of the highest iron-content foods, making it a superfood for preventing anemia. Students learned that Popeye's strength from spinach was based on its exceptional iron content. The legendary iron content of spinach was based on a decimal point error in early nutritional analysis that overstated iron content by 10 times. While spinach does contain iron, it's not exceptionally high compared to other foods, and the iron in spinach is not easily absorbed by the body due to compounds that inhibit iron absorption. The Popeye myth reinforced this nutritional misconception.
  • Nutrition & Health
1980

Reading in Dim Light Damages Eyes

What you learned in school:

Health education taught that reading in poor lighting would permanently damage eyesight and lead to serious vision problems. Students were instructed to always have bright, adequate lighting while reading or studying to protect their eyes. Textbooks warned that dim lighting could cause lasting harm to eye health and development. Teachers emphasized that reading in low light was dangerous and could result in permanent vision impairment, making good lighting a critical safety requirement for all reading activities.

What we know now:

Health education taught that reading in poor lighting would permanently damage eyesight and lead to vision problems. Students were instructed to always have bright lighting while reading or studying. Reading in dim light may cause temporary eye strain, fatigue, and discomfort, but it doesn't cause permanent damage to vision. The eyes are remarkably adaptable to different lighting conditions. While good lighting makes reading more comfortable and may reduce fatigue, poor lighting doesn't cause lasting harm to eye health. This was confusion between temporary discomfort and permanent damage.
  • Nutrition & Health
1980

Swimming After Eating Causes Dangerous Cramps

What you learned in school:

Health and physical education classes taught that swimming within an hour of eating would cause severe stomach cramps that could lead to drowning. Students learned this as a critical safety rule and were required to wait at least an hour after meals before entering the water. Teachers emphasized that food digestion would divert blood flow from muscles, causing dangerous cramping. This was presented as a well-established medical fact that could be life-threatening if ignored.

What we know now:

Health and physical education classes taught that swimming within an hour of eating would cause severe stomach cramps that could lead to drowning. Students learned to wait at least an hour after meals before swimming. There is no scientific evidence that eating before swimming causes dangerous cramps or increases drowning risk. While vigorous exercise immediately after a large meal might cause mild discomfort, it doesn't create life-threatening conditions. This myth may have originated from general advice about intense exercise after eating, but was exaggerated for swimming. Competitive swimmers often eat during long training sessions without problems.
  • Nutrition & Health
1980

Hair and Nails Continue Growing After Death

What you learned in school:

Biology and health education classes taught that hair and fingernails continued to grow for days or weeks after death, creating a spooky image of continued bodily activity. Students learned this as established biological fact, often accompanied by stories of corpses found with noticeably longer hair and nails. Textbooks presented this as evidence of residual cellular activity after death, and it was commonly cited as one of the mysterious aspects of human biology that occurred during the decomposition process.

What we know now:

Biology and health classes taught that hair and fingernails continued to grow for days or weeks after death, creating a spooky image of the body's continued activity. Students learned this as biological fact. Hair and nails don't actually grow after death. The appearance of growth results from the skin shrinking and dehydrating after death, making existing hair and nails more prominent and visible. All cellular activity, including the cell division required for hair and nail growth, stops when the body dies. This is another example of a logical-seeming explanation for an observed phenomenon being incorrect.
  • Technology & Computing
1980

Artificial Intelligence Will Surpass Humans by 1980

What you learned in school:

Computer science classes in the 1960s predicted that artificial intelligence would exceed human intelligence across all domains by 1980. Students learned about imminent computer consciousness and machines that would think better than humans. Textbooks described AI as rapidly approaching human-level intelligence with predictions of superintelligent computers within two decades. The optimism assumed that early AI successes would quickly scale to general intelligence, underestimating the complexity of human cognition.

What we know now:

Computer science classes in the 1960s predicted that artificial intelligence would exceed human intelligence across all domains by 1980. Students learned about imminent computer consciousness and superhuman AI capabilities. AI development has been much slower and more specialized than predicted. While AI excels in specific domains like chess, image recognition, and language processing, general artificial intelligence that matches human cognitive flexibility remains elusive. The challenges of creating truly intelligent machines were underestimated, and progress has been incremental rather than revolutionary.
  • Environmental Science
1980

Acid Rain Is Only a Local Problem

What you learned in school:

Environmental science classes initially taught that acid rain was a localized problem affecting only areas immediately around pollution sources like power plants and factories. Students learned about sulfur dioxide and nitrogen oxides causing acidity in nearby lakes and forests. The problem was presented as contained within a few miles of emission sources. Textbooks focused on local environmental damage without discussing the potential for pollutants to travel long distances through atmospheric circulation.

What we know now:

Environmental science classes initially taught that acid rain was a localized problem affecting only areas immediately around pollution sources. Students learned about sulfur dioxide and nitrogen oxides causing acidity near power plants and factories. Acid rain was discovered to be a regional and international problem, with pollutants traveling hundreds of miles through the atmosphere. Acid precipitation affected forests, lakes, and buildings far from emission sources. This led to international cooperation on air pollution control and demonstrated how environmental problems can cross political boundaries. The scale and reach of acid rain were initially underestimated.
  • Environmental Science
1980

Asbestos Is a Miracle Material

What you learned in school:

Science and health classes taught that asbestos was an ideal building material due to its fire resistance, durability, and excellent insulation properties. Students learned about asbestos as a technological advancement that made buildings safer and more energy-efficient. Textbooks promoted asbestos products as superior alternatives to traditional materials, emphasizing their practical benefits for construction and manufacturing. The material was presented as a modern solution to fire safety and insulation challenges with no mention of health risks.

What we know now:

Science and health classes taught that asbestos was an ideal building material due to its fire resistance, durability, and insulation properties. Students learned about asbestos as a technological advancement that made buildings safer. Asbestos causes mesothelioma, lung cancer, and other serious diseases when its fibers are inhaled. Millions of people developed asbestos-related illnesses from exposure in buildings, ships, and industrial settings. The health risks of asbestos were known to some manufacturers decades before public warnings were issued. Asbestos is now banned or heavily regulated in most countries.
  • Environmental Science
1980

Fossil Fuels Will Last Forever

What you learned in school:

Science classes taught that oil, coal, and natural gas were so abundant that depletion was not a concern for human civilization. Students learned about vast untapped reserves that would last for centuries or millennia. Textbooks presented fossil fuels as essentially unlimited resources, with new discoveries constantly expanding available supplies. The focus was on extraction technology improvements rather than conservation, as scarcity was not considered a realistic possibility.

What we know now:

Science classes taught that oil, coal, and natural gas were so abundant that depletion was not a concern. Students learned about vast untapped reserves that would last for centuries or millennia. While new extraction technologies have extended fossil fuel availability, these resources are finite and becoming more expensive and environmentally damaging to extract. Peak oil theory suggests that conventional oil production has plateaued. Climate change concerns now limit fossil fuel use regardless of availability. The "unlimited" mindset ignored both geological limits and environmental consequences.
  • Geography & Geology
1977

The Deepest Parts of Oceans Are Lifeless

What you learned in school:

Marine biology textbooks taught that the deep ocean below the sunlight zone was a lifeless desert. Students learned that life required sunlight for photosynthesis, making the dark, cold, high-pressure depths uninhabitable. The deep sea was described as a barren wasteland where nothing could survive the extreme conditions.

What we know now:

Marine biology textbooks taught that the deep ocean below the sunlight zone was essentially lifeless - too cold, dark, and high-pressure to support complex life. Students learned that life required sunlight and that the deep sea was a biological desert. The discovery of hydrothermal vents in 1977 revealed thriving ecosystems in the deepest parts of the ocean. These communities are based on chemosynthesis rather than photosynthesis, with unique organisms including giant tube worms, specialized bacteria, and complex food webs completely independent of surface life.
  • Psychology & Social Sciences
1973

Homosexuality Is a Mental Illness

What you learned in school:

Psychology textbooks listed homosexuality as a "sociopathic personality disturbance" and later as a "sexual deviation" in the DSM. Students learned that it was a mental disorder requiring psychiatric treatment and that various therapies could "cure" homosexual patients. Medical schools taught future doctors that same-sex attraction indicated psychological maladjustment.

What we know now:

Psychology textbooks classified homosexuality as a mental disorder that could and should be treated or "cured." Students learned about various conversion therapies and psychological treatments. The American Psychiatric Association removed homosexuality from the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1973, recognizing it as a natural variation of human sexuality. This change was based on scientific research showing that sexual orientation is not a choice or mental illness. Conversion therapy has been discredited and is considered harmful by major mental health organizations.
  • Astronomy & Space
1970

Venus Might Harbor Life Under Its Clouds

What you learned in school:

Science textbooks described Venus as Earth's "sister planet" and speculated about tropical, habitable conditions beneath its mysterious cloud cover. Students learned that the thick atmosphere might hide lush jungles, vast oceans, or even intelligent civilizations. Popular science and science fiction reinforced this image of Venus as a warm, wet world similar to Earth's prehistoric past, making it a prime candidate for life in our solar system.

What we know now:

Science textbooks described Venus as Earth's "sister planet" and speculated about tropical conditions under its cloud cover. Students learned that Venus might have lush jungles and possibly intelligent life. Science fiction often depicted Venus as a jungle planet. Space missions in the 1960s and 1970s revealed Venus to be extremely hostile, with surface temperatures of 900°F (480°C], crushing atmospheric pressure, and clouds of sulfuric acid. The greenhouse effect on Venus creates conditions that would instantly kill any Earth-like life forms.
  • Geography & Geology
1970

Ocean Floors Are Flat and Featureless

What you learned in school:

Geography and oceanography textbooks described ocean floors as vast, flat plains covered in mud from continental erosion. Students learned that the deep ocean was essentially uniform and boring compared to land geology. Before sonar mapping, it was presumed that except for occasional hills, the seafloor was generally featureless and monotonous - a muddy desert stretching endlessly across ocean basins.

What we know now:

Geography classes taught that ocean floors were essentially flat, muddy plains with little topographic variety. Students learned that all the interesting geology was on land. The deep ocean was considered a vast, uniform environment. Sonar mapping during and after World War II revealed dramatic underwater landscapes: mid-ocean ridges, deep trenches, underwater mountains, and complex geological features. The ocean floor is actually more geologically active and varied than most land surfaces, with new crust being created at ridges and destroyed at trenches.
  • Geography & Geology
1970

The Earth's Core Is Solid

What you learned in school:

Geology textbooks through the 1960s described the Earth's core as a single, solid mass of iron and nickel at the planet's center. Students learned about the core as a uniform solid ball, similar to a giant metal sphere, surrounded by the liquid mantle. This model was taught as established geological fact, with diagrams showing the Earth's interior as having distinct solid layers. The concept of a liquid outer core generating magnetic fields was not yet understood or taught in schools.

What we know now:

Geology textbooks described the Earth's core as a solid mass of iron and nickel at the planet's center. Students learned about the core as a single, uniform solid ball surrounded by the mantle. Seismic wave analysis revealed that the Earth actually has two distinct core regions: a liquid outer core of molten iron and nickel, and a solid inner core. The liquid outer core's movement generates Earth's magnetic field through the geodynamo process. This discovery explained how Earth maintains its protective magnetic field and helped understand planetary formation.
  • Geography & Geology
1970

Earthquakes Occur Randomly

What you learned in school:

Geography and earth science textbooks taught that earthquakes were unpredictable natural disasters that could strike anywhere at any time without warning. Students learned that earthquakes were random "acts of God" with no discernible pattern or geographic preference. Maps showed earthquake damage as scattered events across the globe.

What we know now:

Geography classes taught that earthquakes were random, unpredictable events that could happen anywhere at any time. Students learned to view earthquakes as acts of nature with no discernible pattern. While the exact timing remains unpredictable, we now know that most earthquakes occur along specific zones where tectonic plates meet. The "Ring of Fire" around the Pacific, the San Andreas Fault, and other plate boundaries are where the vast majority of earthquakes happen. Understanding plate tectonics has made earthquake-prone regions predictable, even if exact timing isn't.
  • Physics & Chemistry
1970

Lightning Never Strikes the Same Place Twice

What you learned in school:

General science and safety classes taught this as both a scientific principle and safety rule. Students learned that areas recently hit by lightning were safe from future strikes. This was often taught alongside other "common sense" safety principles and used as a metaphor for rare events being unlikely to repeat.

What we know now:

General science classes taught this as a safety principle, suggesting that areas hit by lightning were safe from future strikes. Students learned this as both a literal fact and a metaphor for rare events. Lightning frequently strikes the same locations repeatedly, especially tall structures like skyscrapers, towers, and trees. The Empire State Building is struck about 100 times per year. Lightning follows the path of least electrical resistance, which often means the same route repeatedly. Lightning rods work precisely because lightning does strike the same places multiple times.
  • History
1970

Columbus Discovered America

What you learned in school:

History textbooks taught that Christopher Columbus "discovered" America in 1492, being the first person to find the New World. Students learned that before Columbus, America was unknown to human civilization. Maps and timelines showed 1492 as the "discovery date" when the Americas entered world history for the first time.

What we know now:

History textbooks taught that Christopher Columbus discovered America in 1492, bringing the New World to European attention for the first time. Students learned about Columbus as the bold explorer who found an unknown continent. Indigenous peoples had been living in the Americas for tens of thousands of years before Columbus arrived. Vikings had established settlements in North America around 1000 CE, 500 years before Columbus. Columbus never realized he had reached a new continent - he died believing he had found a route to Asia. The "discovery" narrative ignores the rich civilizations and millions of people already living there.
  • History
1970

Vikings Never Reached America

What you learned in school:

History textbooks taught that Columbus was the first European to reach the Americas in 1492. Students learned that Vikings were limited to European raids and settlements, with no mention of transatlantic voyages. The Norse sagas describing voyages to "Vinland" were dismissed as mythology rather than historical accounts. Textbooks focused on Columbus as the discoverer of the New World, making no reference to earlier Viking expeditions or settlements in North America.

What we know now:

History classes taught that Vikings were limited to Europe and that Columbus was the first European to reach the Americas. Textbooks focused on Viking raids and settlements in Britain and continental Europe. Archaeological evidence at L'Anse aux Meadows in Newfoundland has conclusively proven that Vikings established settlements in North America around 1000 CE. Saga literature that described these voyages, once dismissed as mythology, has been validated by physical evidence. Vikings reached America 500 years before Columbus and established temporary settlements.
  • History
1970

The Wild West Was Extremely Violent

What you learned in school:

History textbooks depicted the American frontier as a lawless wasteland with constant gunfights and daily violence. Students learned about the "Wild West" as a place where life was cheap, law enforcement was absent, and disputes were settled with bullets. Hollywood westerns and popular culture reinforced this image of non-stop violence and chaos.

What we know now:

History classes taught that the American frontier was incredibly violent, with constant gunfights, lawlessness, and death. Students learned about daily shootouts and a complete absence of law and order. Hollywood westerns reinforced this image of constant violence. Historical research shows that murder rates in many Wild West towns were actually lower than in modern American cities. Most frontier towns had functioning legal systems, and violence was often concentrated around specific activities like cattle drives or mining booms. The period was less uniformly violent than popular culture suggests.
  • History
1970

Napoleon Was Unusually Short

What you learned in school:

History textbooks consistently described Napoleon as an unusually short man, often depicting him as barely five feet tall. Students learned that his diminutive stature fueled his aggressive ambitions and military conquests. The term "Napoleon complex" became standard psychology vocabulary to describe short people's compensatory behavior.

What we know now:

History classes taught that Napoleon Bonaparte was exceptionally short, using phrases like "Napoleon complex" to describe aggressive behavior in short people. Students learned that his height contributed to his aggressive military campaigns. Napoleon was actually 5'7" (1.7m], which was average or even slightly above average for men of his era. The confusion arose from differences between French and English measurement systems, and British propaganda that depicted him as short to diminish his stature. His autopsy listed him as 5'2", but this was in French feet, which were larger than English feet.
  • Psychology & Social Sciences
1970

Left-Handed People Are Abnormal

What you learned in school:

Educational psychology taught that left-handedness was a defect, deficiency, or developmental problem that needed correction. Schools systematically forced left-handed children to write with their right hands, often using physical punishment or restraints. Teachers were trained to see left-handedness as abnormal behavior requiring intervention.

What we know now:

Educational psychology taught that left-handedness was a defect that should be corrected. Schools forced left-handed children to write with their right hands, often using punishment to enforce this. Left-handedness was associated with clumsiness, evil, or developmental problems. Left-handedness is simply a natural variation found in about 10% of the population. Forcing children to switch hands can cause learning difficulties, speech problems, and psychological stress. Left-handed people are not abnormal or defective - they simply have different brain organization that can even confer certain advantages in some tasks.
  • Technology & Computing
1970

Computers Will Never Be Smaller Than a Room

What you learned in school:

Computer science and technology classes taught that computers required entire rooms to house the massive vacuum tubes, wiring, and cooling systems needed for operation. Students learned that computers were inherently large machines that only major institutions and corporations could afford or accommodate. Textbooks showed room-sized computers as the permanent reality of computing technology. The idea that computers could become smaller was not discussed, as the vacuum tube technology seemed to set physical limits on miniaturization.

What we know now:

Computer science and technology classes taught that computers required entire rooms to house the massive vacuum tubes, wiring, and cooling systems. Students learned that computers were inherently large machines for institutions and corporations only. The development of transistors, integrated circuits, and microprocessors enabled dramatic miniaturization. Personal computers emerged in the 1970s, laptops in the 1980s, and now smartphones contain more computing power than room-sized computers of the 1950s. The prediction failed to anticipate revolutionary advances in semiconductor technology and component miniaturization.
  • Environmental Science
1970

DDT Is Safe for Humans and Environment

What you learned in school:

Science classes taught that DDT was a miracle pesticide that was completely safe for humans and highly beneficial for agriculture and public health. Students learned about DDT's role in controlling malaria-carrying mosquitoes and increasing crop yields without any mention of environmental concerns. Textbooks presented DDT as a triumph of modern chemistry that would help eliminate insect-borne diseases and feed the world. The focus was entirely on its benefits with no discussion of potential negative effects on wildlife or human health.

What we know now:

Science classes taught that DDT was a miracle pesticide that was completely safe for humans and beneficial for agriculture. Students learned about DDT's role in controlling malaria and increasing crop yields without mentioning environmental concerns. DDT was found to cause cancer in humans, disrupt hormonal systems, and devastate bird populations by thinning their eggshells. Rachel Carson's "Silent Spring" documented these environmental effects. DDT accumulates in the food chain and persists in the environment for decades. It was banned in many countries for agricultural use, though it's still used for malaria control in some regions under strict guidelines.
  • Astronomy & Space
1965

The Universe Is in a Steady State

What you learned in school:

Cosmology textbooks taught the Steady State theory as the leading scientific explanation for the universe. Students learned that the universe had always existed in roughly the same form - expanding but maintaining constant density as new matter was continuously created. This elegant theory, championed by prominent astronomers like Fred Hoyle, avoided the problematic concept of a "creation event" and seemed more scientifically respectable than theories requiring a beginning.

What we know now:

Cosmology classes taught the Steady State theory, which proposed that the universe has always existed in roughly the same form. As it expands, new matter is continuously created to maintain constant density. This was presented as the leading scientific theory, supported by prominent astronomers like Fred Hoyle. The discovery of cosmic microwave background radiation in 1965 provided strong evidence for the Big Bang theory instead. The universe had a definite beginning and has been expanding and cooling ever since. The Steady State theory was largely abandoned by the scientific community.

Science is always evolving. These facts represent our current understanding and may continue to be refined as we learn more.