158 Fun Facts About 9th Grade

What do we call a natural number greater than 1 that is not a product of two smaller numbers?

The primes are the building blocks of every whole number, which is why 1 is left out of the club.

Slope is defined as the ratio of which two things?

Slope is rise over run: the change in y divided by the change in x between two points on the line, so a horizontal line has slope zero.

What is the maximum number of solutions a quadratic equation can have?

The graph is a parabola, and a parabola can cross the x-axis at most twice.

In ax² + bx + c = 0, what is the name given to c?

c is the constant coefficient, or constant term: a is the quadratic coefficient and b the linear coefficient, and if a were zero the equation would just be linear.

Which method is used to derive the quadratic formula?

Completing the square: you rewrite ax² + bx + c = 0 so the left side is a perfect square equal to a constant, then take the square root and solve for x.

The Pythagorean theorem relates the three sides of which kind of triangle?

The Pythagorean theorem holds only in a right triangle: the square of the side opposite the right angle equals the sum of the squares of the other two sides.

What is the name for the side of a right triangle opposite the right angle?

The hypotenuse is the side opposite the right angle and always the longest side, which is why c² = a² + b² in the Pythagorean theorem.

Around what year was Pythagoras born?

Pythagoras was born around 570 BC on the Greek island of Samos and later founded his school at Croton in southern Italy.

Which civilisation used the Pythagorean rule over a thousand years before Pythagoras?

The Babylonians knew the rule by about 1800 BC: the clay tablet Plimpton 322 lists Pythagorean triples more than a thousand years before Pythagoras was born.

The word 'algebra' comes from which language?

It comes from the Arabic al-jabr, 'the reunion of broken parts', which originally referred to setting broken bones before it meant balancing equations.

Which 9th-century Persian mathematician gave algebra its name?

Al-Khwarizmi's treatise on al-jabr wa'l-muqabala, written in Baghdad around 820, gave algebra its name; his own name, Latinised, became the word algorithm.

Which 3rd-century Greek wrote the Arithmetica, an early treatment of solving equations?

His name survives in Diophantine equations, where only whole-number solutions count.

Who proved around 300 BC that there are infinitely many primes?

Euclid's Elements (Book IX, Proposition 20) shows no finite list of primes is complete: multiply them all together, add 1, and the result has a prime factor missing from the list.

What is the only even prime number?

Every other even number is divisible by 2, so every other prime is odd.

Which ancient Greek devised the 'sieve' used to list prime numbers?

The sieve of Eratosthenes, devised in the 3rd century BC, lists primes by writing out the numbers and crossing off every multiple of each prime you find.

The solutions of a linear equation in two variables form what shape on a graph?

Every line in the plane can be written as ax + by + c = 0 and vice versa.

Which form of algebra, taught in schools, uses variables to stand for unspecified values?

Elementary algebra, the kind taught in schools, introduces variables such as x to stand for unknown or unspecified values; abstract algebra, with its groups, rings and fields, comes much later.

What is the basic structural and functional unit of all living things?

The cell is the basic unit of life: every organism is built from one or more cells, and the name comes from the Latin cellula, a small room.

Who discovered cells in 1665, naming them after rooms in a monastery?

Robert Hooke coined the term in Micrographia (1665) after seeing the honeycomb of tiny compartments in a slice of cork, which reminded him of monks' cells.

Which organelles provide energy for cell functions?

Mitochondria are the cell's powerhouses, where cellular respiration breaks down glucose to release usable energy; plant cells have mitochondria as well as chloroplasts.

Bacteria and archaea belong to which broad group of single-celled organisms?

Bacteria and archaea are prokaryotes: cells with no nucleus, whose DNA sits in a region called the nucleoid rather than inside a membrane.

What is the largest membrane-bound organelle in a eukaryotic cell?

It holds the cell's chromosomes inside a double membrane called the nuclear envelope.

What gas do plants release as a by-product of photosynthesis?

The oxygen comes from splitting water molecules in the light-dependent reactions, not from the carbon dioxide the plant takes in.

Which plant pigment absorbs red and blue light and reflects green?

Chlorophyll absorbs red and blue wavelengths to power photosynthesis and reflects green, which is why leaves look green.

What is the name of the light-independent reactions that build sugars in plants?

The Calvin cycle uses the energy carriers made in the light-dependent stage to fix carbon dioxide into three-carbon sugars, which the plant then builds into glucose.

In which part of the chloroplast do the light-dependent reactions of photosynthesis occur?

The light-dependent reactions run in the thylakoid membranes, stacked into grana, where chlorophyll captures light and water is split to release oxygen.

What molecule stores the chemical energy produced by cellular respiration?

ATP, adenosine triphosphate, stores the energy released by respiration in its phosphate bonds; breaking off the third phosphate powers most of the work a cell does.

Which first stage of cellular respiration takes place in the cytosol of every living cell?

Glycolysis, literally 'sugar splitting', breaks one glucose into two pyruvate molecules in the cytosol and works with or without oxygen.

How many ATP molecules per glucose do biology textbooks often say respiration makes?

The textbook maximum is 38 ATP per glucose: 2 from glycolysis, 2 from the Krebs cycle and 34 from the electron transport chain; leaky membranes and transport costs make the real yield nearer 30.

Cell division by mitosis produces how many daughter cells from one parent cell?

Both get an identical set of chromosomes; meiosis is the one that makes four.

Which mitosis stage sees daughter chromosomes pulled toward opposite ends of the cell?

Metaphase lines them up in the middle; anaphase pulls them apart.

Who coined the term 'mitosis' in 1882?

Walther Flemming, who first described chromosome behaviour in dividing salamander cells, coined 'mitosis' in 1882 from the Greek mitos, a warp thread, after the thread-like chromosomes he saw.

What is the name for the process that divides the cytoplasm after mitosis?

Mitosis divides the nucleus; cytokinesis finishes the job by splitting the cell itself.

In DNA, adenine always pairs with which base?

Adenine pairs with thymine by two hydrogen bonds, and guanine with cytosine by three, which keeps the two strands complementary.

What shape do the two strands of DNA coil into?

DNA is a double helix, two strands twisted around a common axis, as modelled in 1953; the strands run in opposite directions, which is why they are called antiparallel.

What sugar is found in each nucleotide of DNA?

Deoxyribose is the sugar in DNA; it lacks one oxygen atom that ribose, the sugar in RNA, carries, which is what 'deoxy' refers to.

Which plant did Gregor Mendel use for his experiments on heredity?

Mendel bred pea plants (Pisum sativum) in the monastery garden at Brno, tracking seven traits including seed colour, plant height and flower position.

In Mendel's second-generation peas, green seeds reappeared in what ratio to yellow?

In the F2 generation Mendel counted 6,022 yellow to 2,001 green seeds, almost exactly 3 to 1, so green reappeared in a 1 to 3 ratio after vanishing entirely in the F1.

What two terms did Mendel coin to describe traits that show or hide in offspring?

Mendel called the trait that shows in hybrids dominant and the hidden one recessive; the invisible 'factors' he proposed are what we now call genes.

In what year did Mendel publish his pea-plant results?

Mendel's paper Experiments on Plant Hybridization appeared in 1866 in the proceedings of the Brno natural history society, and was largely ignored until its rediscovery around 1900.

On which ship did Charles Darwin make his five-year voyage?

Darwin sailed on HMS Beagle for nearly five years under Captain Robert FitzRoy, aboard as a gentleman naturalist rather than a paid crew member.

In which year did Darwin publish On the Origin of Species?

On the Origin of Species was published by John Murray on 24 November 1859, and its first printing of 1,250 copies sold out to booksellers the same day.

Which naturalist sent Darwin an essay in 1858 describing the same idea of natural selection?

Alfred Russel Wallace, writing from the Malay Archipelago, sent Darwin his essay in 1858; the two men's papers were read together at the Linnean Society of London that July.

Where is Charles Darwin buried?

Darwin was buried in Westminster Abbey on 26 April 1882, near Isaac Newton, after scientists and MPs petitioned for it instead of the family's planned grave at Downe.

In a food chain, what is another name for an autotroph such as grass or algae?

Producers, such as grass and algae, make their own food from sunlight and form the first link of every food chain.

Which ecologist introduced the modern concepts of food chains and food webs?

Charles Elton set out food chains and food webs in his 1927 book Animal Ecology; the 9th-century Arab writer al-Jahiz had described such chains centuries earlier in his Book of Animals.

What term describes the non-living components of an ecosystem, such as soil?

Abiotic factors are the non-living parts of an ecosystem, such as soil, water, temperature and sunlight; biotic factors are the living things, linked to them by nutrient cycles and energy flows.

Which organisms release carbon back to the atmosphere by breaking down dead matter?

Decomposers such as fungi and bacteria break dead matter down and respire, returning carbon dioxide to the atmosphere and nutrients to the soil.

Who published the first generally accepted periodic table, in 1869?

Dmitri Mendeleev published his table in 1869, leaving gaps for undiscovered elements and predicting the properties of gallium and germanium before they were found.

How many chemical elements had been officially confirmed as of 2025?

The total reached 118 in 2016, when nihonium, moscovium, tennessine and oganesson were confirmed and named; only the first 94 occur naturally on Earth, the rest are made in laboratories.

Which element has atomic number 1?

Hydrogen, symbol H, has a single proton and so atomic number 1; helium is 2 and lithium is 3.

The rightmost column of the periodic table, group 18, holds which family of elements?

Group 18 is the noble gases, helium through radon, whose full outer electron shells make them almost unreactive; group 1 on the far left is the alkali metals.

The rows of the periodic table are called what?

Rows are periods, each one filling a new electron shell, while columns are groups whose elements tend to behave alike.

Newton's first law expresses which principle?

Newton's first law is the law of inertia: left alone, a body stays at rest or keeps moving in a straight line at constant speed.

In what year did Newton first publish his three laws of motion?

The three laws appeared in 1687 in Newton's Philosophiæ Naturalis Principia Mathematica, written in Latin and published with Edmond Halley's financial backing.

According to Newton's third law, when two bodies push on each other, the forces are what?

The forces are equal in size and opposite in direction, which is why a rocket moves forward as its exhaust is pushed backward.

Newton's second law says net force equals mass multiplied by what?

Net force equals mass times acceleration, F = ma; equivalently, force is the rate at which momentum changes.

Who proposed the theory of continental drift in 1912?

Alfred Wegener, a German meteorologist, proposed continental drift in 1912, arguing from matching coastlines and fossils that the continents had once been joined in a supercontinent, Pangaea.

What is the process called when one tectonic plate is carried down under another?

Subduction carries one plate down beneath another into the mantle; deep ocean trenches such as the Mariana Trench mark where it happens.

Which plate's 'Ring of Fire' holds most of the world's active volcanoes?

The Ring of Fire runs around the edges of the Pacific Plate and holds about three-quarters of the world's active volcanoes, along with most of its earthquakes.

Roughly how far do tectonic plates move each year at most?

The fastest plates, the Pacific Plate among them, move about 10 cm a year, while slow ones such as the Eurasian Plate creep along at 2–3 cm, about the rate fingernails grow.

What is the name for the three types of plate boundary?

Convergent boundaries make mountains and trenches, divergent ones make new sea floor, and transform boundaries, like the San Andreas Fault, slide plates past each other.

What percentage of global evaporation comes from the ocean?

About 86% of the water that evaporates worldwide rises from the oceans, which cover roughly 71% of the planet's surface; the rest comes from land, lakes and rivers.

What is the name for water vapour released from plants into the atmosphere?

Transpiration is the loss of water vapour from plant leaves through their stomata; together with evaporation from soil it is called evapotranspiration.

In which Italian city is Romeo and Juliet set?

The play is set in Verona ('In fair Verona, where we lay our scene') and opens with a street brawl between servants of the feuding Montagues and Capulets.

Which girl is Romeo pining for at the start of the play, before he meets Juliet?

Romeo is pining for Rosaline, a niece of Capulet who has sworn off love; he only goes to the Capulet ball hoping to see her there.

Who secretly marries Romeo and Juliet, hoping to reconcile their families?

Friar Laurence marries them in secret hoping to end the feud, and later gives Juliet the sleeping potion that sets up the tragic ending.

Which hot-headed cousin of Juliet challenges Romeo to a duel?

Tybalt, Juliet's cousin, challenges Romeo after the ball; Romeo, now secretly his kinsman by marriage, refuses, and Tybalt kills Mercutio instead.

Whom does Capulet want Juliet to marry?

Capulet wants Juliet to marry Count Paris, a kinsman of the Prince; he first asks Paris to wait two years, then invites him to the ball.

In what year was Romeo and Juliet first published in quarto?

The first quarto appeared in 1597; it was a garbled 'bad quarto', so the fuller second quarto of 1599 had to correct it.

Who narrates To Kill a Mockingbird?

Scout Finch, Jean Louise, narrates as an adult looking back; she is almost six and Jem nearly ten when the story begins.

In which fictional Alabama town is To Kill a Mockingbird set?

Maycomb is the fictional town, which Harper Lee modelled on her real hometown of Monroeville, Alabama.

Whom does Atticus Finch defend at trial?

Atticus defends Tom Robinson, a Black field hand falsely accused of raping Mayella Ewell, knowing most of Maycomb disapproves.

Which award did To Kill a Mockingbird win the year after it was published?

Published in July 1960, the novel won the Pulitzer Prize for Fiction in 1961 and became a school staple.

What is Dill's real name in To Kill a Mockingbird?

Dill is Charles Baker Harris, who visits Maycomb each summer to stay with his aunt, Miss Rachel Haverford, next door to the Finches.

Who wrote Of Mice and Men?

John Steinbeck published Of Mice and Men in 1937, drawing on his teenage summers working beside migrant farm workers in California's Salinas Valley.

What animals does Lennie dream of tending on his own farm?

Lennie dreams of tending the rabbits on the farm he and George plan to buy; he loves petting soft things, which is exactly what gets him into trouble.

The title Of Mice and Men comes from a poem by which writer?

Robert Burns's 1785 poem To a Mouse gives the line 'the best-laid schemes o' mice an' men / Gang aft agley', usually rendered 'often go awry'.

How much money does Candy offer to put toward the farm in Of Mice and Men?

Candy offers $350: the $250 he was paid for losing his hand plus $100 in savings and wages, in return for living on the farm with George and Lennie.

Which stable hand in Of Mice and Men is isolated from the others because he is black?

Crooks, the crippled Black stable buck, lives apart in the harness room; he scorns the farm dream yet asks whether he could hoe a garden patch there.

Odysseus is king of which island?

Odysseus rules Ithaca, an island off Greece's west coast; his journey home to it from Troy takes ten years on top of the ten-year war.

How many books is the Odyssey divided into?

The Odyssey has 24 books, one per letter of the Greek alphabet, a division made by Alexandrian scholars; the Iliad is split the same way.

How does Penelope put off the suitors in the Odyssey?

Penelope promises to choose a suitor once she finishes a shroud for Odysseus's aged father Laertes, then unweaves each day's work by night for three years.

Which nymph holds Odysseus captive, according to the Old Man of the Sea?

Calypso keeps Odysseus on her island Ogygia for seven years; Proteus, the Old Man of the Sea, tells Menelaus, who passes the news to Telemachus in Sparta.

How many suitors court Penelope in Odysseus's absence?

Telemachus counts 108 suitors in Book 16: 52 from Dulichium, 24 from Same, 20 from Zacynthus and 12 from Ithaca itself.

What object does Ralph use as a horn to gather the boys in Lord of the Flies?

Ralph blows a conch shell found in the lagoon, and holding the conch becomes the rule for who may speak at meetings.

Whose glasses do the boys use to start the signal fire in Lord of the Flies?

Ralph, Jack and Simon do the lighting; Piggy just loses his glasses.

Which children's novel gave William Golding the idea for Lord of the Flies?

Golding took R. M. Ballantyne's The Coral Island (1857), thought its cheerful island boys unrealistic, and set out to write the opposite; Ralph and Jack even share names with Ballantyne's heroes.

In what year was Lord of the Flies published?

Lord of the Flies came out in September 1954 from Faber and Faber; it was Golding's debut novel, turned down by some twenty publishers before Faber took it.

Which two pigs take command after Old Major dies in Animal Farm?

Snowball teaches reading; Napoleon quietly trains a litter of puppies.

Which of the Seven Commandments ends up as the only one on the barn wall?

'All animals are equal' is the seventh commandment; by the end it alone remains on the barn wall, amended to 'but some animals are more equal than others'.

What does Snowball propose building to modernise Animal Farm?

Snowball draws up plans for a windmill to generate electricity; after it collapses in a storm, Napoleon blames Snowball for sabotage.

Which real events did Orwell say Animal Farm reflects?

Orwell said the fable reflected the Russian Revolution and its aftermath; in a 1946 letter to his French translator Yvonne Davet he called it 'a satirical tale against Stalin'.

Which small boar acts as Napoleon's skilled orator and propagandist?

Squealer, a small fat porker with a persuasive voice, is Napoleon's mouthpiece; he convinces the animals the windmill was Napoleon's idea all along.

Who narrates The Great Gatsby?

Nick Carraway narrates; a Yale graduate from the Midwest, he comes east in 1922 to learn the bond business and rents a house next to Gatsby's mansion.

In which Long Island village does Nick rent a bungalow next to Gatsby's estate?

Nick rents in West Egg, the 'less fashionable' of the two eggs, beside Gatsby's mansion; Daisy and Tom live across the bay in old-money East Egg.

What colour is the light Gatsby stares at across the bay?

The green light sits at the end of Daisy's dock in East Egg; Nick first sees Gatsby stretching his arms toward it across the water.

What is Jordan Baker's sport in The Great Gatsby?

Jordan Baker is a golf champion and a childhood friend of Daisy's from Louisville, rumoured to have moved her ball in a tournament.

Which figure of speech makes an implied comparison, without using 'like' or 'as'?

A metaphor states one thing is another: 'All the world's a stage' is the textbook example, where a simile would say the world is like a stage.

Mesopotamia lay between which two rivers?

Mesopotamia, Greek for 'between the rivers', lay between the Tigris and Euphrates, a region roughly matching modern Iraq.

Which king made Babylon the dominant power of Mesopotamia in the 18th century BC?

Hammurabi (reigned c. 1792–1750 BC), sixth king of Babylon's first dynasty, conquered Larsa, Eshnunna and Mari to make Babylon the centre of a Mesopotamian empire; his law code survives on a diorite stele.

Which ruler united Upper and Lower Egypt around 3150 BC?

Menes is the traditional unifier of Upper and Lower Egypt around 3150 BC and founder of the First Dynasty; most Egyptologists identify him with Narmer, whose palette shows both crowns.

During which period were the Giza pyramids and the Great Sphinx built?

The Giza pyramids and the Sphinx were built in the Old Kingdom's Fourth Dynasty, around 2600–2500 BC, a thousand years before the New Kingdom's peak of power.

Which discovery let scholars finally decipher hieroglyphs in the 1820s?

The Rosetta Stone, found in 1799, carries the same decree in hieroglyphs, Demotic and Greek; Thomas Young and then Jean-François Champollion, in 1822, used it to crack the script.

Which pharaoh fought the Hittites at Kadesh and later made peace with them by treaty?

Ramesses II fought the Hittites at Kadesh around 1274 BC and later sealed a treaty with Hattusili III, one of the earliest surviving peace treaties; he reigned for 66 years.

At which 480 BC pass did three hundred Spartans hold off the Persians for days?

At Thermopylae in 480 BC, Leonidas and his 300 Spartans, with several thousand other Greeks, held the narrow pass against Xerxes' army for three days before being outflanked.

The Peloponnesian War was fought between Athens and which rival city-state?

Sparta led the Peloponnesian League against Athens from 431 to 404 BC; a plague early in the war killed the Athenian statesman Pericles.

How many kings ruled the Spartan state at the same time?

Alongside a council of elders and five officials called ephors.

Which philosopher tutored the young Alexander the Great?

Aristotle tutored Alexander at Mieza from about 343 BC; Plutarch says Alexander kept a copy of the Iliad annotated by Aristotle under his pillow on campaign.

In which city did Alexander the Great die in 323 BC?

Alexander died in Babylon in June 323 BC, aged 32, in the palace of Nebuchadnezzar II; he had planned to make the city the capital of his empire.

Which Persian king did Alexander overthrow?

Darius III lost to Alexander at Issus in 333 BC and Gaugamela in 331 BC, then fled east and was murdered by his own satrap Bessus in 330 BC.

Which river did Julius Caesar cross with his army in 49 BC, defying the Senate?

Caesar crossed the Rubicon, the boundary between Cisalpine Gaul and Italy, in January 49 BC, starting a civil war; 'crossing the Rubicon' became a phrase for passing a point of no return.

On what date was Julius Caesar assassinated?

Caesar was stabbed on the Ides of March, 15 March 44 BC, at a Senate meeting in the Theatre of Pompey; the conspirators were led by Brutus and Cassius.

With Crassus and Pompey, Caesar formed which informal alliance in 60 BC?

The First Triumvirate, an informal pact of 60 BC, dominated Roman politics until Crassus died at Carrhae in 53 BC and Caesar and Pompey fell out.

Which title did the Senate grant Octavian in 27 BC, making him the first emperor?

The Senate granted Octavian the name Augustus, 'the venerated', on 16 January 27 BC; he also took the title princeps, foremost citizen.

Under which emperor did Rome reach its greatest territorial extent?

Under Trajan the empire reached its greatest extent in AD 117, after his conquests of Dacia and Mesopotamia; his successor Hadrian gave up the eastern gains.

Which emperor moved the imperial seat to Byzantium in 330 and renamed it Constantinople?

Constantine refounded Byzantium as Constantinople, dedicating it on 11 May 330 as his 'New Rome'; he had legalised Christianity with the Edict of Milan in 313.

In what year did the Western Roman Empire fall?

In 476 the Germanic general Odoacer deposed the boy emperor Romulus Augustulus, the date usually taken as the fall of the West; the Eastern empire lasted until 1453.

What was the name for the two centuries of stability that began with the first emperor?

The Pax Romana, literally 'Roman peace', ran from Augustus's accession in 27 BC to the death of Marcus Aurelius in AD 180.

Which English king sealed Magna Carta at Runnymede in 1215?

King John sealed Magna Carta at Runnymede on 15 June 1215; Pope Innocent III annulled it within months, sparking the First Barons' War.

How many original 1215 copies of Magna Carta survive?

Four 1215 originals survive: two at the British Library, one at Lincoln Castle and one at Salisbury Cathedral.

Which bacterium caused the Black Death?

Yersinia pestis, the plague bacterium, is mainly spread by the bites of infected fleas; in its pneumonic form it also passes by respiratory droplets.

Up to how many people did the Black Death kill in Europe between 1346 and 1353?

Estimates run as high as 50 million deaths in Europe between 1346 and 1353, roughly a third to a half of the continent's 14th-century population.

The Black Death reportedly entered Europe during a 1347 siege of which Crimean port?

At Caffa, the Genoese trading post in Crimea, the besieging Mongol army reportedly catapulted plague corpses over the walls in 1347; Genoese ships then carried the disease to Sicily and across the Mediterranean.

In which Italian city did the Renaissance begin?

The Renaissance began in Florence in the 14th century, where the wealth of its bankers and the Medici family's patronage funded artists and scholars.

Which two polymaths inspired the term 'Renaissance man'?

Leonardo da Vinci and Michelangelo, who each painted, sculpted, engineered and studied anatomy, are the archetypal 'Renaissance men' the term evokes.

Which architect built the great cathedral dome after losing the 1401 Baptistery doors contest?

Filippo Brunelleschi lost the 1401 Baptistery doors contest to Ghiberti, then engineered the dome of Florence Cathedral (1420–1436), raised without a wooden centering frame.

Which Florentine political thinker tried to describe politics 'as it really was'?

Niccolò Machiavelli, in The Prince (written 1513), set out to describe how rulers actually behave rather than how they ought to; his name became the adjective 'Machiavellian' for cunning statecraft.

What was stormed in Paris on 14 July 1789?

The Bastille, a royal fortress and prison in eastern Paris, was stormed by a crowd seeking its store of gunpowder; 14 July later became France's national day.

How many prisoners were actually inside the Paris fortress stormed on 14 July 1789?

Only seven prisoners were inside: four forgers, two men held as insane and the Comte de Solages, an aristocrat locked up at his family's request; the attackers wanted the gunpowder.

What did the Third Estate deputies swear when they found their meeting hall locked?

The Tennis Court Oath of 20 June 1789: locked out of their hall at Versailles, the deputies met in a royal tennis court and vowed not to disperse until France had a constitution.

Who led the radical Jacobins on the Committee of Public Safety during the Terror?

Maximilien Robespierre dominated the Committee of Public Safety from July 1793 until his own execution on 28 July 1794; about 16,000 people were guillotined during the Terror.

In what month and year was Louis XVI executed?

Louis XVI was guillotined on 21 January 1793 in the Place de la Révolution; the monarchy had been abolished and the First Republic proclaimed in September 1792, four months earlier.

In which country did the Industrial Revolution begin around 1760?

The Industrial Revolution began in Great Britain around 1760, driven by coal, canals and steam power, and had spread to continental Europe and the US by about 1840.

Who invented the spinning jenny in 1764?

James Hargreaves, a Lancashire weaver, built the spinning jenny around 1764, letting one worker spin eight threads at once; Arkwright's water frame followed five years later.

The cotton gin sped up removing seed from cotton by roughly what factor?

Eli Whitney's 1793 gin let one worker clean about 50 pounds of cotton a day instead of one by hand, roughly a 50-fold gain that made upland cotton economical to grow at scale.

Which industry was the first to use modern production methods in the Industrial Revolution?

Textiles, cotton above all, were the first industry to adopt machine production in mills, and became the dominant industry by employment, output and invested capital.

Whose assassination in Sarajevo on 28 June 1914 triggered World War I?

Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, was shot with his wife Sophie by Gavrilo Princip, a Bosnian Serb, in Sarajevo on 28 June 1914.

What made the United States join the Allies in April 1917?

Germany resumed unrestricted submarine warfare on 1 February 1917, gambling it could starve Britain before American troops arrived; that, plus the Zimmermann Telegram, brought the US declaration of war on 6 April.

On what date did the armistice ending World War I take effect?

The armistice signed in Foch's railway carriage at Compiègne took effect at 11 a.m. on 11 November 1918; Kaiser Wilhelm II had abdicated on 9 November.

Which 1919 settlement made Germany lose territory, disarm and pay reparations?

The Treaty of Versailles, signed on 28 June 1919, stripped Germany of territory and colonies, capped its army at 100,000 men and imposed reparations.

Which gas did Germany first use at the Second Battle of Ypres in April 1915?

Germany released chlorine gas from thousands of cylinders at Ypres on 22 April 1915, the first large-scale use of a lethal gas, in breach of the 1899 Hague Declaration on asphyxiating gases.

Which failed Allied campaign followed the Ottoman Empire joining the Central Powers?

The Gallipoli campaign of 1915–16 tried to force the Dardanelles and knock the Ottomans out of the war after they joined the Central Powers in late 1914; the Allies evacuated in January 1916.

Which 1962 standoff is considered the closest the Cold War came to nuclear war?

The Cuban Missile Crisis of October 1962 began when US spy planes found Soviet missile sites in Cuba; Khrushchev withdrew them for a US no-invasion pledge and the quiet removal of Jupiter missiles from Turkey.

In which year did the Soviet Union dissolve, ending the Cold War?

The Soviet Union formally dissolved on 26 December 1991, a day after Gorbachev resigned; his reforms had already helped trigger the 1989 revolutions in the Eastern Bloc.

Which Soviet-led alliance was formed in 1955 to match NATO?

The Warsaw Pact was signed in May 1955 by the USSR and seven Eastern Bloc states, days after West Germany joined NATO, which had been founded in 1949.

In Ray Bradbury's Fahrenheit 451, what is Guy Montag's job?

Montag is a fireman whose job in Bradbury's 1953 novel is burning books; he grows disillusioned with destroying literature and ends up among the exiles who memorise it.

Elie Wiesel's memoir Night recounts his time with his father in Auschwitz and which other camp?

The book ends shortly after the US Army liberated Buchenwald in April 1945.

An element's atomic number equals the number of what in each of its atoms?

For ordinary nuclei, that proton count is what places an element in the periodic table.

What attraction holds sodium chloride, table salt, together as a solid?

Ionic bonding is the electrostatic attraction between oppositely charged ions, Na⁺ and Cl⁻ in table salt; shared electron pairs make covalent bonds and free electrons hold metals together.

Roughly what is Avogadro's number, the number of particles in one mole?

It is an SI defining constant with the exact value 6.02214076 × 10²³ per mole.

Which formula gives the circumference of a circle with radius r?

Circumference is 2πr; since the diameter is twice the radius, that equals π times the diameter, while πr² gives the area.

Who is the teenage narrator of J. D. Salinger's The Catcher in the Rye?

Holden Caulfield, sixteen, narrates from a rest home after being expelled from Pencey Prep; the 1951 novel made him an icon of teenage rebellion.

From which Spanish port did Columbus sail with three ships in August 1492?

Columbus sailed from Palos de la Frontera on 3 August 1492 with the Niña, Pinta and Santa María, making landfall on 12 October on a Bahamian island its inhabitants called Guanahani.

The hertz, the SI unit of frequency, equals one cycle per what?

A 60 Hz mains supply, for example, cycles sixty times every second.

Density is defined as the ratio of a substance's mass to its what?

Density is mass divided by volume, which is why a kilogram of feathers takes up far more space than a kilogram of lead.

Osmosis is the net movement of solvent molecules through what kind of membrane?

Osmosis happens across a selectively permeable membrane that lets water through but not dissolved solutes; water moves from lower to higher solute concentration until the two sides even out.

In Great Expectations, which escaped convict accosts young Pip in a graveyard?

Abel Magwitch, an escaped convict from the prison hulks, seizes Pip among the graves on the Kent marshes and later becomes his secret benefactor.