50 Fun Facts About 10th Grade

Which country, spanning eleven time zones and bordering fourteen others, is the largest on Earth?

Russia is the largest country on Earth yet only the ninth most populous, with just over 140 million people.

Which organ, the heaviest inside the human body, produces bile and stores around 100 g of glycogen?

The liver is the only human internal organ that regenerates naturally: as little as 25% of it can regrow into a whole liver.

Which organelle, the site of aerobic respiration, has its own DNA, inherited only from the mother?

The mitochondrion has a genome like a bacterium's, supporting the theory that it began as a free-living microbe engulfed by an early cell.

Which 1803 deal with Napoleon's France nearly doubled the size of the United States for $15 million?

The Louisiana Purchase worked out at less than three cents an acre, and Napoleon sold because war with Britain was imminent.

Which planet, the largest in the solar system, hosts the Great Red Spot, a storm tracked since the 1800s?

Jupiter's Great Red Spot has been observed continuously since 1878 and whips up winds of nearly 500 km/h.

Which explorer's fleet first circled the globe, though its commander was killed in the Philippines?

Magellan left Spain with five ships and about 270 men; only the Victoria, under Elcano, completed the voyage, almost exactly three years later.

Which amendment to the US Constitution, ratified in December 1865, abolished slavery nationwide?

The Thirteenth Amendment still allows involuntary servitude 'as a punishment for crime', the loophole behind convict leasing and prison labor.

Which mathematician, as a boy, reputedly summed 1 to 100 in seconds by pairing numbers into 101s?

Carl Friedrich Gauss simply multiplied 50 by 101 to get 5050, the trick behind the arithmetic-series formula n(n+1)/2.

Which continent, though a polar desert, locks up about 70% of the world's fresh water as ice?

Antarctica's ice averages 1.9 km thick and would raise global sea levels by almost 60 meters if it all melted.

Which novella satirizing Stalin's Soviet Union ends with pigs walking upright and carrying whips?

Animal Farm's final commandment reads 'All animals are equal, but some animals are more equal than others', and the pigs end up indistinguishable from the men.

Which element, first identified as a distinct gas by Henry Cavendish, makes up 75% of normal matter?

Hydrogen was Cavendish's 'inflammable air'; Lavoisier later named it from the Greek for 'water-former' after showing it burns to make water.

Which photosynthetic pigment absorbs red and blue light but reflects the wavelengths in between?

Chlorophyll is why autumn leaves turn yellow: as it breaks down, the carotenoids that were there all summer finally show through.

Which property, the subject of Newton's first law, throws bus riders forward when the driver brakes?

Inertia is the tendency of a mass to resist any change in its motion, which is why Newton's first law is also called the principle of inertia.

Which law, set out by a German physicist in 1827, makes current in a wire proportional to voltage?

Ohm's law is the reason resistance is measured in ohms: Georg Ohm found the rule by testing wires of different lengths in simple circuits.

On the pH scale, what value marks neutral pure water at 25 °C, with acids below it and bases above?

A pH of 7 is neutral because H+ and OH− ions are present in equal amounts, and each step on the scale is a tenfold change in acidity.

What is the approximate speed of light in a vacuum, the constant c in Einstein's equation E = mc²?

Light covers about 300,000 km/s, so the sunlight reaching Earth left the Sun a little over eight minutes earlier.

Mendel's monohybrid cross of two heterozygous pea plants gave what ratio of dominant to recessive traits?

The 3:1 ratio appears because a recessive trait shows only when both alleles are recessive, which happens in one offspring in four.

Which brain structure, tucked under the cerebral hemispheres, coordinates fine movement and balance?

The cerebellum packs in more neurons than the rest of the brain combined while taking up only about 10% of its volume.

Which alkali metal, atomic number 11, is stored under oil and is soft enough to cut with a knife?

Sodium's best-known compound is table salt, NaCl, yet the pure metal is so reactive it has to be kept in oil or an inert gas.

Which optical effect, far stronger at short wavelengths, makes the daytime sky blue and sunsets red?

Rayleigh scattering varies inversely with the fourth power of wavelength, so blue light is scattered far more than red as sunlight crosses the air.

Which eye defect, where distant objects focus in front of the retina, does a diverging lens correct?

Myopia is the most common eye disorder, affecting an estimated 1.5 billion people — about 22% of the world — and rates have climbed since the 1950s.

Which leaf pores, usually more numerous on the underside, open and close to control gas exchange?

Stomata are flanked by two guard cells that bow apart as they swell with water, opening the pore, and relax to close it again.

Which gas, released when baking soda meets vinegar, turns clear limewater milky?

Carbon dioxide reacts with the calcium hydroxide in limewater to precipitate insoluble calcium carbonate, the same compound as chalk.

Whose periodic table left gaps for undiscovered elements, rightly predicting gallium and germanium?

Dmitri Mendeleev called them eka-aluminium and eka-silicon, and he also foresaw scandium; his 1869 table ran by atomic weight, not atomic number.

Which of DNA's four bases is missing from RNA, where uracil takes its place?

Thymine is simply uracil with a methyl group bolted on, which is why chemists also call it 5-methyluracil.

A right triangle has legs of 8 and 15; what hypotenuse completes this primitive Pythagorean triple?

17 completes the 8-15-17 triple; the Babylonian tablet Plimpton 322 listed such triples around 1800 BC, long before Pythagoras.

What value of the discriminant b² − 4ac gives a quadratic equation exactly one repeated real root?

A zero discriminant means the parabola just touches the x-axis at a single point, so the two roots collapse into one double root.

What is the sum of the interior angles of a hexagon, the shape bees use for honeycomb cells?

720° split six ways gives the 120° corners that let regular hexagons tile a plane with no gaps, three meeting at every vertex.

Which Greek mathematician's treatise Elements proved that there are infinitely many prime numbers?

Euclid's proof still works: multiply any finite list of primes together, add one, and the result has a prime factor missing from the list.

In a 30-60-90 right triangle, the side opposite the 30° angle is what fraction of the hypotenuse?

1/2 follows because a 30-60-90 triangle is half an equilateral triangle, which is also why sin 30° equals exactly one half.

Which number, the count of squares on a chessboard, is both the square and the cube of an integer?

64 is 8², 4³ and 2⁶ all at once, which makes it a sixth power — the first one after 1.

What term describes an integer such as 6 or 28 that equals the sum of its proper divisors?

Perfect numbers are scarce: every one ever found is even, and whether an odd perfect number exists remains an open problem.

What is 1 + 3 + 5 + ... + 23, the sum of the first twelve odd numbers?

144 is 12², because the sum of the first n odd numbers is always n²: add an L-shaped layer to a square and you get the next square.

Which charter, sealed by King John at Runnymede in 1215, still has three clauses in force today?

Magna Carta's surviving clauses come from the 1297 reissue; the 1215 original also named 25 barons to hold the king to his word.

Whose 1914 assassination in Sarajevo by Gavrilo Princip set off the July Crisis and World War I?

Franz Ferdinand died because his driver took a wrong turn and stalled the car while reversing, right where Princip was standing.

Which 1917 uprising, led by Lenin's Bolsheviks in Petrograd, overthrew the Provisional Government?

The October Revolution began on 7 November by today's calendar; the country still used the Julian calendar, which ran 13 days behind.

Which Mughal emperor built the Taj Mahal as the tomb of his favorite consort, Mumtaz Mahal?

Shah Jahan spent his final years imprisoned by his son Aurangzeb in Agra Fort, from 1658 until his death in 1666.

Which 1930 protest, a 24-day walk by Gandhi to the sea at Dandi, defied a British tax monopoly?

The Salt March covered 387 km, and when Gandhi boiled salty mud in seawater at Dandi to make illegal salt, millions followed him into civil disobedience.

Which circle of latitude, near 23.4° north, is the farthest north the Sun can be directly overhead?

The Tropic of Cancer is drifting south about 15 m a year as Earth's tilt wobbles, and it runs through India, Egypt, Mexico and China.

Which mountain range, pushed up by India's collision with Eurasia, still rises about 5 mm a year?

The Himalayas include the world's highest peaks, and their limestone was laid down as sand, mud and shells on the Neo-Tethys seabed.

Which 14 km-wide channel separates Spain from Morocco and joins the Atlantic to the Mediterranean?

The Strait of Gibraltar was sealed about six million years ago, and when the Atlantic broke back through in the Zanclean flood, 5.33 million years ago, it refilled the Mediterranean.

Which lawyer defends Tom Robinson against a rape charge in Harper Lee's To Kill a Mockingbird?

Atticus Finch was modeled on Harper Lee's own father, Amasa Coleman Lee, an Alabama lawyer who likewise defended Black clients.

In The Great Gatsby, what color is the light on Daisy's dock that Gatsby stares at across the bay?

The green light is read as Gatsby's unreachable dream of winning Daisy — and, by extension, the American Dream — glimpsed across Long Island Sound.

In Lord of the Flies, what does Ralph use to call the boys together, an object smashed when Piggy dies?

The conch stands for order and the right to speak, so when Roger's boulder kills Piggy and smashes it, the island's last rule dies too.

Which Italian city is the setting for the Montague–Capulet feud in Shakespeare's Romeo and Juliet?

Verona's famous 'Juliet's balcony' is a tourist invention: the play only puts Juliet at a window, and 'balcony' wasn't even an English word yet.

Which power, claimed in Marbury v. Madison, allows laws that violate the Constitution to be struck down?

Judicial review appears nowhere in the Constitution's text; Chief Justice John Marshall claimed it for the courts in 1803 and it has held ever since.

What minimum age does Article Two of the US Constitution set for anyone to serve as President?

35 is the highest of the three age floors in the Constitution: 25 for the House, 30 for the Senate and 35 for the presidency.

Which UN body, with five veto-wielding permanent members, can impose sanctions and authorize force?

The Security Council is the only UN body whose resolutions bind every member state, and its permanent five are the Second World War's victors.

What share of both houses of Congress does it take to override a presidential veto in the US?

Two-thirds is also the share of the Senate needed to convict in an impeachment trial and remove an official from office.

Which language has the most native speakers worldwide, roughly double runner-up Spanish's total?

Mandarin Chinese has about 988 million native speakers against Spanish's 487 million, with English third at 372 million.