Neither cracking one's knuckles nor exercising while in good health causes osteoarthritis.
2. All humans learn in fundamentally similar ways. In particular, there is no evidence that people have different learning styles, nor that catering teaching styles to purported learning styles improves information retention.
3. The idea that lightning never strikes the same place twice is one of the oldest and best known superstitions about lightning. There is no reason that lightning would not be able to strike the same place twice; if there is a thunderstorm in a given area, then objects and places which are more prominent or conductive (and therefore minimize distance) are more likely to be struck. For instance, lightning strikes the Empire State Building in New York City about 100 times per year.
4. A penny dropped from the Empire State Building will not kill a person or crack the sidewalk. The terminal velocity of a falling penny is about 30–50 miles per hour (50–80 km/h), and the penny will not exceed that speed regardless of the height from which it is dropped. At that speed, its energy is not enough to penetrate a human skull or crack concrete, as demonstrated on an episode of MythBusters. As MythBusters noted, the Empire State Building is a particularly poor setting for this misconception, since its tapered shape would make it impossible to drop anything directly from the top to street level. MythBusters also pointed out that this doesn't mean that dropping coins from high altitude is safe. It might still cause harm.
5. Swallowed chewing gum does not take seven years to digest. In fact, chewing gum is mostly indigestible, and passes through the digestive system at the same rate as other matter.
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Eating less than an hour before swimming does not increase the risk of experiencing muscle cramps or drowning. One study shows a correlation between alcohol consumption and drowning, but there is no evidence cited regarding stomach cramps or the consumption of food.
7. All different tastes can be detected on all parts of the tongue by taste buds, with slightly increased sensitivities in different locations depending on the person, contrary to the popular belief that specific tastes only correspond to specific mapped sites on the tongue. The original tongue map was based on a mistranslation of a 1901 German thesis by Edwin Boring. In addition, the current common categorical conception is there are not 4 but 5 primary tastes. In addition to bitter, sour, salty, and sweet, humans have taste receptors for umami, which is a savory or meaty taste.
8. There is no evidence that obesity is related to slower resting metabolism. Resting metabolic rate doesn't vary much between people. Weight gain and loss are directly attributable to diet and activity. Overweight people tend to underestimate the amount of food they eat, and underweight people tend to overestimate.
9. Schizophrenia is not split or multiple personality disorder; i.e., dissociative identity disorder. The term was coined from the Greek roots schizein and phrēn, "to split" and "mind", in reference to a "splitting of mental functions", seen in schizophrenia, not a splitting of the personality.
10. Dyslexia is not a cognitive disorder characterized by the reversal of letters or words and mirror writing. It is a disorder of people who have at least average intelligence and who have difficulty in spelling words, reading quickly, writing words, "sounding out" words in the head, pronouncing words when reading aloud and understanding what they read. Although some dyslexics also have problems with letter reversal, that is not a symptom that is characteristic of dyslexia.
Earwigs are not known to purposefully climb into external ear canals, though there have been anecdotal reports of earwigs being found in the ear. Entomologists suggest that the origin of the name is actually a reference to the appearance of the hindwings, which are unique and distinctive among insects, and resemble a human ear when unfolded.
12. Drinking milk or consuming other dairy products does not increase mucus production. As a result, they do not need to be avoided by those with the flu or cold congestion.
13. Rust does not cause tetanus infection. The Clostridium tetani bacterium is generally found in dirty environments. Since the same conditions that harbor tetanus bacteria also promote rusting of metal, many people associate rust with tetanus. C. tetani requires anoxic conditions to reproduce and these are found in the permeable layers of rust that form on oxygen-absorbing, unprotected ironwork.
14. James Watt did not invent the steam engine, nor were his ideas on steam engine power inspired by a kettle lid pressured open by steam. Watt improved upon the already commercially successful Newcomen atmospheric engine in the 1760s and 1770s, making certain improvements critical to its future usage, particularly the external condenser, increasing its efficiency, and later the mechanism for transforming reciprocating motion into rotary motion; his new steam engine later gained huge fame as a result.
15. A vegetarian or vegan diet can provide enough protein for adequate nutrition. In fact, typical protein intakes of ovo-lacto vegetarians and vegans meet and exceed requirements. However, a vegan diet does require supplementation of vitamin B12 for optimal health.
Drowning is often inconspicuous to onlookers. In most cases, raising the arms and vocalizing are impossible due to the instinctive drowning response. Waving and yelling (known as "aquatic distress") is a sign of trouble, but not a dependable one: most victims demonstrating the instinctive drowning response do not show prior evidence of distress.
17. Humans have more than the commonly cited five senses. The number of senses in various categorizations ranges from 5 to more than 20. In addition to sight, smell, taste, touch, and hearing, which were the senses identified by Aristotle, humans can sense balance and acceleration (equilibrioception), pain (nociception), body and limb position (proprioception or kinesthetic sense), and relative temperature (thermoception). Other senses sometimes identified are the sense of time, itching, pressure, hunger, thirst, fullness of the stomach, need to urinate, need to defecate, and blood carbon dioxide levels.
18. There is no physiological basis for the belief that having sex in the days leading up to a sporting event or contest is detrimental to performance. In fact it has been suggested that sex prior to sports activity can elevate the levels of testosterone in males, which could potentially enhance their performance.
19. Gyroscopic forces or geometric trail are not required for a rider to balance a bicycle or for it to demonstrate self-stability. Although gyroscopic forces and trail can be contributing factors, it has been demonstrated that those factors are neither required nor sufficient by themselves.
20. Thomas Edison did not invent the light bulb. He did, however, develop the first practical light bulb in 1880 (employing a carbonized bamboo filament), shortly prior to Joseph Swan, who invented an even more efficient bulb in 1881 (which used a cellulose filament).
Seasons are not caused by the Earth being closer to the Sun in the summer than in the winter. In fact, the Earth is farthest from the Sun when it is summer in the Northern Hemisphere. Seasons are caused by Earth's 23.4-degree axial tilt. In July, the Northern Hemisphere is tilted towards the Sun resulting in longer days and more direct sunlight; in January, it is tilted away. The seasons are reversed in the Southern Hemisphere, which is tilted towards the Sun in January and away from the Sun in July.
22. While it was praised by one architectural magazine prior to its construction as "the best high apartment of the year", the Pruitt–Igoe housing project in St. Louis, Missouri, considered to epitomize the failures of urban renewal in American cities after it was demolished in the early 1970s, never won any awards for its design. The architectural firm that designed the buildings did win an award for an earlier St. Louis project, which may have been confused with Pruitt–Igoe.
23. The common image of Santa Claus (Father Christmas) as a jolly old man in red robes was not created by The Coca-Cola Company as an advertising gimmick. Despite being historically represented with different characteristics in different colours of robes, Santa Claus had already taken his modern form in popular culture and seen extensive use in other companies' advertisements and other mass media at the time Coca-Cola began using his image in the 1930s.
24. People do not use only 10% of their brains. While it is true that a small minority of neurons in the brain are actively firing at any one time, the inactive neurons are important too. This misconception has been commonplace in American culture at least as far back as the start of the 20th century, and was attributed to William James, who apparently used the expression metaphorically.
25. Alcohol does not necessarily kill brain cells. Alcohol can, however, lead indirectly to the death of brain cells in two ways: (1) In chronic, heavy alcohol users whose brains have adapted to the effects of alcohol, abrupt cessation following heavy use can cause excitotoxicity leading to cellular death in multiple areas of the brain. (2) In alcoholics who get most of their daily calories from alcohol, a deficiency of thiamine can produce Korsakoff's syndrome, which is associated with serious brain damage.