1.1The three rules of cell theory

1. All living things are made of one or more cells. A bacterium, a gum tree and you are all built from the same kind of unit.
2. The cell is the basic unit of structure and function in living things. Every job a body does — digesting, moving, sensing — happens because cells do it.
3. All cells come from pre‑existing cells. Cells only ever appear by an existing cell dividing. Life does not start from nothing.

1.2Working the microscope

Cells are measured in micrometres (µm). One micrometre is a thousandth of a millimetre. A typical animal cell is about 20 µm across — you could line up fifty of them across a single millimetre. That is why you need a light microscope, and why the practical exam questions are always about using one properly.

Total magnification

You multiply the two lenses. Nothing else.

Making a wet mount

1. Put one drop of water in the middle of a clean slide.
2. Add the specimen — a piece of onion epidermis, a cheek scraping, a leaf peel.
3. Add a drop of stain. Iodine stains starch and plant nuclei; methylene blue stains animal nuclei. Without stain, most parts of a cell are transparent and you see almost nothing.
4. Lower the coverslip at an angle using a mounting needle, then let it fall. Going slowly is what stops air bubbles — a bubble looks like a thick black ring and gets mistaken for a cell every year.
5. Start on the lowest objective, focus with the coarse knob, centre what you want, then switch up and use only the fine focus.

2.1The animal cell

Study the labelled version first. Then scroll to the drag-and-drop drill below and do it from memory — that is the part that actually makes it stick.

2.2The plant cell

A plant cell has everything an animal cell has, plus three extras: a cell wall, chloroplasts and one large permanent vacuole. Those three explain almost everything else about plants — why they hold their shape, why they are green, and why a thirsty plant wilts.

2.3Every organelle, and its one job

3.1The five levels of organisation

3.2Specialised cells

A cell that specialises changes its shape and its contents to suit one job. In the exam you are given a picture or a description and asked how is this cell adapted to its function? — and the answer is always structure first, then what that structure lets it do.

3.3How substances actually get in and out

4.1The two kinds of digestion

4.2The journey, organ by organ

1. Mouth. Teeth chew (mechanical). Saliva adds amylase, which starts breaking starch into sugars, and mucus to make a slippery ball of food called a bolus.
2. Oesophagus. No digestion here. Rings of muscle squeeze in waves — peristalsis — pushing the bolus down. This is why an astronaut can swallow upside down; gravity is not doing the work.
3. Stomach. A muscular bag that churns for 2–4 hours. It releases hydrochloric acid (kills most bacteria and gives protease the acidic pH it needs) and protease, which starts on proteins. Food leaves as a soup called chyme.
4. Small intestine — digestion. The first part, the duodenum, receives bile from the gall bladder and enzymes from the pancreas. Chemical digestion is finished here.
5. Small intestine — absorption. In the long second part, the small food molecules pass through the wall into the blood. About 6 m long and lined with millions of finger-like villi.
6. Large intestine. What is left is mostly water and fibre. Water and some minerals are absorbed back into the blood; gut bacteria feed on the fibre and make some vitamins.
7. Rectum and anus. The solid waste, faeces, is stored and then egested. Note the word: egestion is removing undigested food that never entered a cell — not the same as excretion.

4.3Enzymes: the three you must know

An enzyme is a biological catalyst — a protein that speeds up a reaction without being used up. Each one only fits one kind of molecule, and each works best at a particular temperature and pH. Learn this table as three rows of three.

4.4Why the small intestine is shaped the way it is

Absorption is diffusion — so the small intestine is built for the three things that make diffusion fast: huge surface area, short distance, steep gradient.

5.1The heart, chamber by chamber

Four chambers. Two on top called atria that receive blood, two underneath called ventricles that pump it out. The right side handles blood coming back from the body; the left side handles blood coming back from the lungs.

5.2Four structures, four reasons

5.3Double circulation

Blood passes through the heart twice for every full lap of the body. That is what "double circulation" means, and it is why mammals can be so active: the blood is re-pressurised after the lungs instead of trickling on to the body.

5.4Three kinds of blood vessel

5.5What blood is made of

6.1The route air takes

6.2How you breathe in and out

Air always moves from high pressure to low pressure. Your muscles change the volume of the chest, that changes the pressure inside, and air follows. Nothing sucks; everything is pushed.

6.3The alveolus: where the exchange happens

There are roughly 300 million alveoli in a pair of lungs. Spread flat they would cover about half a tennis court — all of it packed inside your chest, all of it one cell thick.

7.1Three organs that excrete

7.2Homeostasis: staying the same on the inside

Homeostasis is keeping the conditions inside your body steady while the outside world changes. Enzymes only work in a narrow range, so your body defends that range hard: temperature near 37 °C, blood water and salt near constant, blood glucose near constant, blood pH near 7.4.

8.1The reaction everything is for

8.2What happens when you sprint

Exam questions love this scenario, because answering it well means describing several systems responding together to one change.

1. Muscle cells respire faster, so they use up glucose and oxygen quickly and produce more carbon dioxide.
2. Sensors detect the rising carbon dioxide in the blood.
3. Breathing rate and depth increase — more oxygen into the blood, more carbon dioxide out.
4. Heart rate increases — blood is delivered to the muscles faster, so oxygen and glucose arrive faster and waste is removed faster.
5. Blood vessels to the muscles widen; vessels to the digestive system narrow. Delivery is prioritised where it is needed.
6. You get hot, so you sweat and your skin flushes — the excretory and circulatory systems cooling you down.
7. If oxygen still cannot arrive fast enough, muscles switch to anaerobic respiration: glucose → lactic acid + a little energy. Lactic acid builds up, the muscle aches, and you keep breathing hard afterwards to repay the oxygen debt.

1.1Solid, liquid, gas

1.2Changing state

• Melting — solid → liquid, at the melting point (ice: 0 °C).
• Evaporating / boiling — liquid → gas. Evaporation happens from the surface at any temperature; boiling happens throughout the liquid at the boiling point (water: 100 °C).
• Condensing — gas → liquid. Why a cold drink "sweats" on a hot day.
• Freezing — liquid → solid, at the same temperature as melting.
• Diffusion — particles of a gas or liquid spreading out and mixing by their own random movement — why perfume crosses a room.

2.1Symbols: chemistry's alphabet

Every element has a one- or two-letter symbol. The first letter is always a capital, the second is always lowercase — Co is cobalt but CO is carbon monoxide, a compound of two elements. Some symbols come from Latin names, which is why they look nothing like the English word.

2.2Metals and non-metals

3.1Element, compound or mixture? Read the particles

3.2Reading a formula

A formula counts atoms. The little number applies only to the symbol just before it: H₂O is two hydrogens and one oxygen; CO₂ is one carbon and two oxygens. No number means one.

4.1Solution words

• A solution is a mixture where one substance has dissolved in another — you cannot see the parts. Salt water is the classic.
• The solute is what dissolves (the salt). The solvent is what it dissolves in (the water).
• Soluble means it can dissolve; insoluble means it cannot (sand in water).
• A suspension is an insoluble solid floating through a liquid — muddy water. It settles if you wait.

4.2Pick the right separation

5.1Two changes, side by side

5.2The five indicators of a chemical change

1. A permanent colour change — toast browning, a copper roof turning green.
2. A gas is produced (bubbles) when nothing was boiling — sherbet fizzing on your tongue, vinegar on bicarb.
3. A precipitate forms — two clear liquids make a solid that clouds the mixture.
4. Temperature changes by itself — the mixture gets hot (exothermic) or cold (endothermic) without a stove.
5. Light or sound is given off — a firework, a glow stick, a burning match.

1.1The two family trees

2.1Three ways heat travels

• Conduction — vibrating particles bump their neighbours, passing energy along. Works best in solids; metals are superb at it, which is why a metal seat feels colder than a wooden one at the same temperature.
• Convection — in liquids and gases, warm fluid expands, becomes less dense and rises; cooler fluid sinks to replace it, making a loop. Why heaters go near the floor and air conditioners near the ceiling.
• Radiation — energy travelling as rays that need no particles at all. The only transfer that works through empty space.
• An insulator is a material heat crosses slowly — wool, foam, trapped air. That is the whole science of a puffer jacket.

3.1The skater: one story, told twice

3.2Flow diagrams: the exam's favourite

Write the forms in order with arrows. Name the object above the arrow if you can.

4.1Useful energy and wasted energy

1.1Cooling speed writes the crystal size

2.1Four steps, millions of years

3.1Before and after

• The heat comes from depth and from nearby magma; the pressure comes from kilometres of rock above and from colliding tectonic plates.
• Pressure often flattens the new crystals into stripes or sheets — that banding is a metamorphic giveaway.
• The change happens in the solid state, over thousands to millions of years.

4.1The cycle

4.2Deep time

1.1Adding and subtracting

1.2Multiplying and dividing

2.1The three laws

3.1Percentage of an amount

1. Turn the percentage into a decimal (divide by 100): 35% → 0.35.
2. Multiply: 35% of $80 = 0.35 × 80 = $28.
3. Discount? Subtract from the original: $80 − $28 = $52. Shortcut: a 35% discount means you pay 65%, so 0.65 × 80 = $52 in one step.
4. Increase? Same shortcut upward: a 10% rise means paying 110%, so × 1.10.

3.2Sharing in a ratio

• Simplify a ratio like a fraction: 12 : 18 → divide both by 6 → 2 : 3.
• A rate compares different units: 180 km in 2 hours = 90 km/h. Divide to get the "per one".
• Best buy: work out the price per unit for each option and pick the smaller. 500 g for $6 (1.2 c/g) beats 300 g for $4.20 (1.4 c/g).

4.1The four skills

5.1A live graph you can edit

5.2What m and c each do

1. To plot a line: make a small table. For y = 2x + 1, x = 0 gives y = 1, x = 1 gives 3, x = 2 gives 5. Plot the points, rule the line.
2. To read a graph: c is where it crosses the y-axis; m is rise ÷ run between any two grid points.
3. To check a point is on a line: substitute. Is (3, 7) on y = 2x + 1? 2(3) + 1 = 7 ✓ yes.

6.1The circle, labelled

6.2Volume of a prism

• Area of a triangle = ½ × base × height, so a triangular prism's volume = ½bh × length.
• Units stack with the dimension: length cm, area cm², volume cm³. Writing the wrong unit loses a mark even with the right number.
• 1 cm³ holds exactly 1 mL — volume and capacity are the same idea.

1.1The chain every response follows

• A neuron is a nerve cell: branched dendrites collect the signal, the long axon carries it, often wrapped in a fatty myelin sheath that speeds it up.
• Neurons never quite touch. The gap is a synapse, crossed by chemical messengers — this is where the signal briefly becomes chemistry.
• Receptors by sense: light → eye, sound and balance → ear, chemicals → nose and tongue, touch/heat/pain → skin.

1.2The reflex arc: skipping the brain

2.1Nerves vs hormones

• Pancreas → insulin (lowers blood glucose) and glucagon (raises it).
• Adrenal glands → adrenaline: the fight-or-flight surge — faster heart, wider airways, glucose released.
• Thyroid → thyroxine: sets the body's idle speed (metabolism).
• Pituitary → growth hormone, and the "master gland" signals that run other glands.

2.2Negative feedback: the thermostat trick

3.1The cast list

• Biotic factors are the living parts: plants, animals, fungi, bacteria — and their interactions (predation, competition).
• Abiotic factors are the non-living conditions: sunlight, temperature, water, soil, shelter.
• Producers (plants, algae) make their own food by photosynthesis. Every chain starts with one.
• Consumers eat others: herbivores eat plants, carnivores eat animals, omnivores eat both.
• Decomposers (fungi, bacteria) break down the dead and return nutrients to the soil — the recyclers nothing works without.

3.2A food web, read properly

4.1The energy pyramid

4.2Matter loops: carbon in four moves

1. Photosynthesis pulls carbon dioxide out of the air and locks the carbon into plant sugar.
2. Feeding passes that carbon up the chain, body to body.
3. Respiration — by plants, animals AND decomposers — breathes carbon dioxide back out.
4. Decomposition returns the carbon in dead bodies and waste to the soil and air, ready to be used again. (Burning fossil fuels is a fifth, human-added move: it releases carbon that was locked away for millions of years.)

1.1A lithium atom, labelled

1.2The two numbers

2.1Three famous families

• Metals fill the left and centre (about three quarters of the table); non-metals sit top-right; a staircase of semi-metals divides them.
• Same column = same outer-electron count = same chemistry family. That single idea is the table's superpower: it predicted undiscovered elements.
• Reading a table cell: the small whole number is the atomic number (protons); the larger number is the (average) atomic mass.

3.1One reaction, drawn as atoms

3.2Word equations

• The starting substances are reactants; the new substances are products. The arrow means "react to make": reactants → products.
• Methane + oxygen → carbon dioxide + water.
• Iron + oxygen + water → hydrated iron oxide (rust).
• Signs a reaction happened are the Year 8 five: colour change, gas, precipitate, temperature change, light/sound.

4.1The four patterns

4.2Energy in, energy out

• Exothermic reactions release energy — the mixture (and its surroundings) get hotter. Combustion, hand warmers, respiration.
• Endothermic reactions absorb energy — the mixture gets colder. Instant cold packs, photosynthesis, baking soda + vinegar.
• Test in one line: put a thermometer in. Temperature up → exo; down → endo.

1.1Anatomy of a wave

1.2Two shapes of wave

2.1The two dials: pitch and loudness

• Humans hear roughly 20 Hz to 20,000 Hz. Dogs hear higher; whales and elephants rumble lower.
• Sound needs a medium. No particles → nothing to pass the vibration → silence. Space is silent; the bell-in-a-vacuum-jar experiment proves it.
• Speed depends on the medium: about 340 m/s in air, ~1,500 m/s in water, ~5,000 m/s in steel. Tighter-packed particles pass the shake faster — the old ear-on-the-railway-track trick.
• Light travels about a million times faster than sound — so you see lightning, then count the seconds to the thunder (3 seconds ≈ 1 km).
• An echo is sound reflected off a hard surface. Sonar and bat navigation both time the echo to measure distance.

3.1Reflection and refraction, one diagram each

• White light is a mix. A prism refracts each colour by a slightly different amount and fans it into a spectrum — dispersion. Raindrops do the same thing: a rainbow.
• Red bends least, violet bends most.
• A red apple looks red because it reflects red light and absorbs the other colours. A white object reflects them all; a black one absorbs them all (and warms up).
• Materials are transparent (glass — light straight through), translucent (frosted glass — light through, scrambled), or opaque (wood — no light through; makes shadows).

4.1The three quantities

4.2Series vs parallel: the diagram that decides your house wiring

1.1The layers

1.2The plates

• The rigid outer shell is cracked into about fifteen tectonic plates that fit together like a spherical jigsaw, carrying continents and ocean floor alike.
• They ride the mantle's convection currents at 2–10 cm a year — fingernail speed. Over 100 million years that is thousands of kilometres.
• Almost all earthquakes and volcanoes happen at plate edges. Map the quakes and you have drawn the plate boundaries — the Pacific's ring of them is the famous Ring of Fire.
• Australia sits mid-plate, which is why it has so few big quakes — and it is drifting north about 7 cm a year, fast enough that GPS maps must be corrected.

2.1The three boundaries

3.1Four lines of evidence

1. The jigsaw fit. South America and Africa's coastlines match like torn halves of one page — and they fit even better at the true continental edges under the sea.
2. Matching fossils. The same land reptile (Mesosaurus) and the same fern (Glossopteris) are fossilised on continents now separated by oceans no land animal could cross. Either the animals swam the Atlantic — or the lands were joined.
3. Matching rocks and mountains. Rock bands in eastern South America line up exactly with bands in western Africa; the Appalachians continue into the Scottish Highlands.
4. The clincher: seafloor spreading. In the 1960s, surveys found mid-ocean ridges with brand-new rock at the crest and progressively older rock further away, in matching stripes on both sides. The ocean floor is a conveyor belt made at ridges and consumed in trenches — the missing engine, found.

4.1The cycle

• The four spheres: atmosphere (air), biosphere (life), hydrosphere (water and ice), geosphere (rock and soil). The carbon cycle threads through all four.
• The ocean holds far more carbon than the air and constantly trades CO₂ with it across the surface.
• CO₂ is a greenhouse gas: it lets sunlight in but slows heat's escape. More CO₂ in the air means more trapped heat — the mechanism behind the warming climate.
• Deforestation hits the cycle twice: fewer trees photosynthesising carbon in, and burning or rotting the wood sends its stored carbon out.

1.1The three laws

1.2Scientific notation

A number in scientific notation is written as (a number from 1 up to but not including 10) × (a power of 10). The power counts how many places the decimal point moved.

1. Big numbers, positive power. 149 000 000 = 1.49 × 10⁸ — the point moved 8 places left.
2. Small numbers, negative power. 0.00052 = 5.2 × 10⁻⁴ — the point moved 4 places right.
3. Check the first part. 14.9 × 10⁷ is not scientific notation — 14.9 is too big; shift once more: 1.49 × 10⁸.

2.1Single brackets, both directions

1. Expand: the outside term multiplies every term inside. 3(2x + 5) = 6x + 15. Watch signs: −2(x − 4) = −2x + 8.
2. Factorise: pull out the highest common factor. 6x + 15 = 3(2x + 5). For 8x² + 12x the HCF is 4x: 4x(2x + 3).
3. Check by expanding back. Factorising is only right if expanding your answer returns the original. This check takes ten seconds and catches everything.

2.2Double brackets: the area model

1. Every term in the first bracket multiplies every term in the second. (x + 2)(x + 3) = x² + 3x + 2x + 6.
2. Collect the like terms in the middle. 3x + 2x = 5x, so the answer is x² + 5x + 6.
3. Signs ride along. (x − 4)(x + 2) = x² + 2x − 4x − 8 = x² − 2x − 8.

3.1Gradient from any two points

Between points (x₁, y₁) and (x₂, y₂): m = (y₂ − y₁) ÷ (x₂ − x₁) — rise over run. Between (1, 3) and (4, 9): m = (9 − 3) ÷ (4 − 1) = 6 ÷ 3 = 2. The midpoint is just the average of each coordinate: ((1+4)/2, (3+9)/2) = (2.5, 6).

3.2Your first curve

4.1Pythagoras' theorem

1. Finding the hypotenuse: add. Sides 6 and 8: c² = 36 + 64 = 100, so c = 10.
2. Finding a short side: subtract. Hypotenuse 13, one side 5: a² = 169 − 25 = 144, so a = 12.
3. It only works with the right angle. No right angle, no Pythagoras — that's what the little square in the corner is telling you.

4.2SOH CAH TOA

1. Label the sides from the angle you know (or want). Opposite, adjacent, hypotenuse.
2. Pick the ratio that uses your two sides. Know the hypotenuse, want the opposite? That's O and H — sine.
3. Solve. Hypotenuse 10, θ = 30°: opposite = 10 × sin 30° = 10 × 0.5 = 5.

1.1Word classes: the job a word is doing

1.2Phrase vs clause

• A phrase is a group of words without a subject–verb pair: "under the old bridge", "the tall girl", "before lunch". It adds detail but cannot stand alone.
• A clause has both a subject (who or what) and a verb (what they do): "the dog barked".
• A main clause makes sense on its own: "We went home." A subordinate clause starts with a word like although, when, because, if and leaves you hanging: "although it was late…" — it needs a main clause to lean on.

1.3The three sentence types

2.1Apostrophes: two jobs, no more

• Contraction — the apostrophe marks missing letters: do not → don't, it is → it's.
• Possession — the apostrophe shows ownership: the student's book (one student), the students' books (more than one — apostrophe after the s).
• Apostrophes are never used just because a word is plural. "Banana's $2/kg" is the classic greengrocer's error.
• The famous pair: it's always means it is or it has. its (no apostrophe) means belonging to it — like his and hers, which take no apostrophe either.

2.2Commas — and the comma splice

• Commas separate items in a list, mark off extra information, and follow a subordinate clause that starts a sentence: "When the bell rang, we left."
• A comma splice is the error of gluing two complete sentences with only a comma: "It was late, we went home." A comma is not strong enough for that job.
• Three legal fixes: a full stop ("It was late. We went home."), a conjunction ("It was late, so we went home."), or a semicolon ("It was late; we went home.").

2.3Punctuating dialogue

1. New speaker, new line. Every change of speaker starts a new paragraph.
2. Speech marks wrap only the spoken words: "Let's go," said Sam.
3. The punctuation before the closing quote stays inside it — a comma if a speech tag follows ("Let's go," said Sam), the full stop if not.
4. The speech tag stays lower-case after speech: …" said Sam — unless it is a name.

2.4Homophones: same sound, different word

3.1Start with audience and purpose

• Audience: who is this written for? A principal, Year 7s and grandparents need different language, examples and tone.
• Purpose: what is it trying to do — persuade, inform, entertain? Persuasive texts want you to think or do something.
• Every technique below is chosen to suit the audience. Statistics impress a school board; a sad story about one puppy moves the general public.

3.2The three appeals

3.3The techniques toolbox

4.1Narrative structure: the shape of tension

4.2Point of view: who is telling this?

• First person ("I") — a character inside the story tells it. Intimate, but we only know what they know — and they might be wrong, or lying.
• Third person limited ("she", "he") — an outside narrator who sticks to one character's thoughts and experiences.
• Third person omniscient — an all-knowing narrator who can enter any character's head and see everything, everywhere.
• POV is a choice with consequences: a mystery told by the detective hides different secrets than one told by the culprit.

4.3Figurative language: pictures made of words

1.1The feudal pyramid

1.2Life on the manor

• The manor was the basic unit of medieval life: the lord's house or castle, a village, farmland, common pasture and a church. Most people were born, worked and died on one manor.
• A serf was not a slave — he could not be bought and sold — but he was tied to the land: he could not leave, marry or even grind his grain elsewhere without the lord's permission, and he owed the lord several days of unpaid work every week.
• Villagers farmed long strips scattered across two or three great open fields, leaving one field fallow (unplanted) each year so the soil could recover.
• Famine was a constant fear: one bad harvest meant hunger, two in a row meant starvation. Most peasants never travelled more than a day's walk from home.

1.3The power of the Church

• Medieval western Europe had one Church — the Catholic Church, led by the Pope — and almost everyone belonged to it. People genuinely believed their eternal fate depended on it.
• The Church ran the things governments run today: schools, hospitals, care for the poor. Monasteries copied the books that kept learning alive.
• It was also enormously rich: every family paid a tithe — one tenth of what they produced — and the Church held vast lands.
• Its ultimate weapon was excommunication: being expelled from the Church, which people believed shut the gates of heaven. Even kings feared it.

2.1How it spread

2.2What caused it — then and now

• The most common form, bubonic plague, caused fever and painful swollen lumps — buboes — in the armpits, neck and groin.
• Because people blamed sin, some became flagellants, marching from town to town whipping themselves in public to beg God's forgiveness — and spreading the disease as they went.
• Doctors' remedies — bleeding patients, sweet-smelling herbs, aromatic vinegar — did nothing, because the true cause was invisible to them: germs would not be discovered for another 500 years.

2.3The consequences

1. Catastrophic death toll. Historians estimate between a third and a half of Europe's population died — roughly 25 to 50 million people. Some towns lost more; a few remote areas escaped almost untouched. (The exact number is contested — medieval record-keeping collapsed along with everything else.)
2. Labour shortage. Suddenly there were too few workers for the land. Surviving peasants could demand wages, or walk to a lord who would pay them — unthinkable before.
3. Lords pushed back. England's Statute of Labourers (1351) tried to freeze wages at pre-plague levels. Resentment at laws like this helped fuel the English Peasants' Revolt of 1381.
4. Feudalism weakened. Serfdom didn't vanish overnight, but the old deal — work for protection, never for pay — was broken in western Europe. The Church's authority also suffered: prayers had not stopped the dying.

3.1The Tokugawa social order

After a century of civil war, Tokugawa Ieyasu won the decisive Battle of Sekigahara in 1600 and became shogun in 1603. The emperor remained in Kyoto as a revered figurehead — but real power sat with the shogun in Edo (today's Tokyo). Below him, society was frozen into ranked classes. You were born into your class, dressed according to it, and almost never left it.

• Samurai lived by bushido, "the way of the warrior": absolute loyalty to your lord, courage, self-discipline and honour valued above life itself. A disgraced samurai was expected to die rather than live with shame.
• Compare this with European chivalry: both were warrior codes tied to a lord — but bushido put loyalty and honour first, where chivalry (in theory) put protecting the weak and serving God.

3.2Sakoku: the closed country

• Why close the country? The shoguns feared Christianity and European influence would divide Japanese loyalties and invite conquest — they had watched European powers colonise elsewhere in Asia.
• Isolation was not total: one carefully guarded window stayed open. Dutch and Chinese traders could dock at the tiny artificial island of Dejima in Nagasaki harbour — Japan's only official peephole on the world.
• The result was two centuries of internal peace: cities, roads, theatre, woodblock printing and literacy flourished — while Japan's military technology stood still, which is exactly what Perry's cannon exposed in 1853.

4.1The Viking Age, 793–1066

4.2Raiders, traders, settlers — three faces, one people

4.3The longship — the technology behind it all

• Longships were fast under sail or oar, and their genius was a shallow draught: they needed so little water that they could row far up rivers and land directly on beaches — no harbour required. That made surprise raids possible, and escape easy.
• The same shipbuilding skill produced broader, deeper cargo ships (knarrs) that carried settlers, livestock and trade goods across open ocean to Iceland and Greenland.
• Vikings navigated without compasses — by sun, stars, landmarks, birds and hard-won sea knowledge.
• Settlement changed them: in England the Danelaw Vikings became Christian farmers within a few generations, and their words — sky, egg, knife, they — are still in English.