Monday, May 30, 2011

List of common misconceptions Part IV Science

Astronomy

A satellite image of a section of the Great Wall of China, running diagonally from lower left to upper right (not to be confused with the much more prominent river running from upper left to lower right). The region pictured is 12 × 12 km (7.5 × 7.5 miles).
  • It is commonly claimed that the Great Wall of China is the only man-made object visible from the Moon. This is false. None of the Apollo astronauts reported seeing any specific man-made object from the Moon, and even earth-orbiting astronauts can barely see it, but city lights are easily visible on the night side of Earth from orbit.[55] The misconception is believed to have been popularized by Richard Halliburton decades before the first moon landing. Shuttle astronaut Jay Apt has been quoted as saying "…the Great Wall is almost invisible from only 180 miles up."[56] (See Man-made structures visible from space.)
  • Black holes, unlike their common image, do not necessarily suck up all the matter in the vicinity. They can act as "cosmic vacuum cleaners", but not as much as some people might think.[57] The collapse of a star into a black hole is an explosive process, which means, according to Mass–energy equivalence, that the resulting black hole would be of lower mass than its parent object, and actually have a weaker gravitational pull.[58] The source of the confusion comes from the fact that a black hole exists in a space much smaller but orders of magnitude more dense than a star, causing its gravitational pull to be much stronger closer to its surface. But, as an example, were the Sun to be replaced by a black hole of the same mass, then the orbits of all the planets surrounding it would be unaffected. This is because "if you're outside the event horizon, you can just keep going around in circles around [a black hole], in exactly the same way that you can be in orbit around any other kind of mass."[59]
  • Seasons are not caused by the Earth being closer to the Sun in the summer than in the winter. In fact, the Earth is actually farther from the Sun when it is summer in the Northern Hemisphere. Seasons are the result of the Earth being tilted on its axis by 23.4 degrees. As the Earth orbits the Sun, different parts of the world receive different amounts of direct sunlight. When an area of the Earth's surface is oriented perpendicular to the incoming sunlight, it will receive more radiation than it will when it is oriented at an angle to the incoming sunlight. In July, the Northern Hemisphere is tilted towards the Sun giving 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.[60][61]

Biology

Bombus pratorum over an Echinacea purpurea inflorescence; a widespread myth holds that bumblebees should be incapable of flight.
  • The claim[62] that a duck's quack does not echo is false, although the echo may be difficult to hear for humans under some circumstances.[63]
  • DNA is not made of protein.[64][65] DNA is instead a nucleic acid. DNA and protein are closely interrelated, however. DNA is always accompanied by proteins in the chromatin of plants and animals.[66] See protein biosynthesis for DNA's involvement in assembling protein. See DNA replication for enzymatic proteins' involvement in assembling DNA.
  • The notion that goldfish have a memory span of just a few seconds is false.[67][68][69]
  • Lemmings do not engage in mass suicidal dives off cliffs when migrating. They will, however, occasionally unintentionally fall off cliffs when venturing into unknown territory, with no knowledge of the boundaries of the environment. This misconception was popularized by theDisney film White Wilderness, which shot many of the migration scenes (also staged by using multiple shots of different groups of lemmings) on a large, snow-covered turntable in a studio. Photographers later pushed the lemmings off a cliff.[70] The misconception itself is much older, dating back to at least the late nineteenth century.[71]
  • Bats are not blind. While many (most) bat species use echolocation as a primary sense, all bat species have eyes and are capable of sight. Further, not all bats can echolocate and these bats have excellent night vision (see megabat, vs. microbat).[72][73][74]
  • It is a common myth that an earthworm becomes two worms when cut in half. However, only a limited number of earthworm species[75] are capable of anterior regeneration. When most earthworms are bisected, only the front half of the worm (where the mouth is located) can survive, while the other half dies.[76] Also, species of the planaria family of flatwormsactually do become two new planaria when bisected or split down the middle.[77]
  • According to urban myth, the daddy longlegs spider (Pholcus phalangioides) is the most venomous spider in the world, but the shape of their mandibles leaves them unable to bite humans, rendering them harmless to our species. In reality, they can indeed pierce human skin, though the tiny amount of venom they carry causes only a mild burning sensation for a few seconds.[78] In addition, there is also confusion regarding the use of the name daddy longlegs, because harvestmen (order Opiliones, which are not spiders) and crane flies(which are insects) are also known as daddy longlegs, and share (also incorrectly) the myth of being venomous.[79][80]
  • Poinsettias are not highly toxic. While it is true that they are mildly irritating to the skin or stomach[81] and may sometimes cause diarrhea and vomiting if eaten,[82] an American Journal of Emergency Medicine study of 22,793 cases reported to the American Association of Poison Control Centers showed no fatalities, and furthermore that a strong majority of poinsettia exposures are accidental, involve children, and usually do not result in any type of medical treatment.[83] Additionally, Poinsettias are not highly toxic to cats. According to the ASPCA, poinsettias may cause light to mid-range gastrointestinal discomfort in felines, with diarrhea and vomiting as the most severe consequences of ingestion.[84]
  • The flight mechanism and aerodynamics of the bumblebee (as well as other insects) are actually quite well understood, in spite of the urban legend that calculations show that they should not be able to fly. In the 1930s a German scientist, using flawed techniques, indeed postulated that bumblebees theoretically should not be able to fly,[85] although he later retracted the suggestion. However, the hypothesis became generalized to the false notion that "scientists think that bumblebees should not be able to fly."
  • Sharks can actually suffer from cancer. The myth that sharks do not get cancer was spread by the 1992 book Sharks Don't Get Cancer by I. William Lane and used to sell extracts of shark cartilage as cancer prevention treatments. Reports of carcinomas in sharks exist, and current data do not allow any speculation about the incidence of tumors in sharks.[86]
  • It is not harmful to baby birds to pick them up and return them to their nests, despite the common belief that doing so will cause the mother to reject them.[87][88]
  • Bulls are not enraged by the color red, used in capes by professional matadors. Cattle are dichromats, so red does not stand out as a bright color. It is not the color of the cape that angers the bull, but rather the movement of the fabric that irritates the bull and incites it to charge.[89][90][91]
  • Contrary to popular belief, dogs do not sweat by salivating.[92][93][94][95][96][97][98][99] It is not true that dogs do not have sweat glands or have sweat glands only on their tongues. They do sweat, mainly through the footpads.

Evolution

  • The word theory in the theory of evolution does not imply mainstream scientific doubt regarding its validity; the concepts of theory andhypothesis have specific meanings in a scientific context. While theory in colloquial usage may denote a hunch or conjecture, a scientific theory is a set of principles that explains observable phenomena in natural terms.[100][101] Evolution is a theory in the same sense as germ theory, gravitation, or plate tectonics.[102]
A reconstruction of Aegyptopithecus, a primate predating the split between the human and Old World monkey lineages inhuman evolution.
  • Humans did not evolve from chimpanzees[103] or any other modern-day primates. Humans and monkeys share a common ancestor that lived about 40 million years ago.[104] This common ancestor diverged into separate lineages, one evolving into so-called New World monkeys and the other into Old World monkeys and apes.[105] Humans are part of the Hominidae (great ape) family, which also includes chimpanzees, gorillas, and orangutans. Similarly, the common ancestor of humans and chimpanzees, which lived between 5 and 8 million years ago, evolved into two lineages, one eventually becoming modern humans and the other the two extant chimpanzeespecies.[106]
  • Evolution is not a progression from inferior to superior organisms, and it also does not necessarily result in an increase in complexity. A population can evolve to become simpler, having a smaller genome, but devolution is a misnomer.[107][108]
  • According to the California Academy of Sciences, around 41% of U.S. adults mistakenly believe humans and dinosaurs coexisted.[109]However, the last of the non-avian dinosaurs died 65.5 million years ago, after the Cretaceous–Tertiary extinction event, whereas the earliestHomo genus (humans) evolved between 2.3 and 2.4 million years ago.
  • Evolution does not violate the Second Law of Thermodynamics. A common argument against evolution is that entropy, according to the Second Law of Thermodynamics, increases over time, and thus evolution could not produce increased complexity. However, the law does not refer to complexity and only applies to closed systems,[110] which the Earth is not, as it absorbs and radiates the Sun's energy.[111]
  • Evolution does not "plan" to improve an organism's fitness to survive.[112][113] For example, an incorrect way to describe giraffe evolution is to say that giraffe necks grew longer over time because they needed to reach tall trees. Evolution doesn't see a need and respond to it. This mistaken view is known as Lamarckism. A mutation resulting in longer necks would be more likely to benefit an animal in an area with tall trees than an area with short trees, and thus enhance the chance of the animal surviving to pass on its longer-necked genes. Tall trees could not cause the mutation nor would they cause a higher percentage of animals to be born with longer necks.[114]
  • Mammals did not evolve from reptiles. Mammals (synapsids) and reptiles (sauropsids) diverged about 320 million years ago, in the Carboniferous period. Their last common ancestors were a group of primitive reptile-like animals known as amniotes. Amniotes, which had a solely land-based existence, had evolved from reptile-like amphibians (reptiliomorphs), but were not yet reptiles. The misconception that mammals evolved from reptiles arose from a once common practice of using the word "reptile" very loosely: the ancestors of mammals (synapsids) were sometimes called "mammal-like reptiles", a term that modern biologists avoid. An example of a so-called "mammal-like reptile" is Dimetrodon, which is often thought of as a dinosaur, but is in fact neither a dinosaur nor even a reptile.[115]

Chemistry

  • Glass is not a high-viscosity liquid at room temperature: it is an amorphous solid, although it does have some chemical properties normally associated with liquids. Panes of stained glass windows often have thicker glass at the bottom than at the top, and this has been cited as an example of the slow flow of glass over centuries. However, this unevenness is due to the window manufacturing processes used in earlier eras, which produced glass panes that were unevenly thick at the time of their installation. Normally the thick end of glass would be installed at the bottom of the frame, but it is also common to find old windows where the thicker end has been installed to the sides or the top. In fact, the lead frames of the windows are less viscous than the panes, and if glass was indeed a slow moving liquid, the panes would warp at a higher degree.[116][117]

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