If you graduated in 1945…
Here’s what your teachers got wrong.

Humans evolved from monkeys or apes.

Humans and modern apes share a common ancestor. We did not evolve from any living ape species. The common ancestor lived 6-8 million years ago.

Moss grows on the north side of trees, so you can use it as a compass if lost in the woods.

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

The Great Wall of China is the only human-made object visible from space (or from the Moon).

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

Betsy Ross designed and sewed the first American flag.

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

The Emancipation Proclamation freed all slaves in the United States.

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

Vikings discovered America but then vanished without leaving a lasting presence.

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

George Washington's dentures were carved from wood.

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

Infinity is infinity. There is only one infinite quantity, and all infinities are the same size.

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

The angles in any triangle always add up to exactly 180 degrees.

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

1 is a prime number.

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

Mathematics is a complete formal system: any true mathematical statement can eventually be proved.

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

In random sequences, a streak of one outcome makes the opposite outcome more likely; the 'law of averages' must balance things out.

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

You cannot take the square root of a negative number. It is undefined and mathematically impossible.

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

Margarine is healthier than butter because it is lower in saturated fat.

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

Spinach is an excellent source of iron because it contains much more iron than other vegetables.

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

Pterodactyls and pterosaurs were dinosaurs.

Pterosaurs were flying reptiles, not dinosaurs. Dinosaurs belong to the clade Dinosauria; pterosaurs belong to Pterosauria. They are close relatives but distinct groups.

Light and electromagnetic waves travel through a medium called the 'luminiferous aether' that fills all space.

Light does not require a medium. Einstein's special relativity (1905) and the Michelson-Morley experiment (1887) disproved the aether.