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Science
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Science
Why the sky is blue
The sky is blue because air scatters blue light about six times more than red. See why sunsets turn red and…
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Science
Rainbows
A rainbow is sunlight bent and bounced inside raindrops. See why it is an arc, why red is on the outside, and…
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Science
Why the sea is salty
The sea is salty because rivers carry dissolved minerals from rock into it and evaporation leaves them…
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Science
How tides work
Tides come from the Moon's gravity pulling on the sea. See why there are two high tides a day, why each comes…
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Science
Why ice floats
Ice floats because water expands as it freezes, making ice about 8% less dense than liquid water. See why…
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Science
How soap works
Soap molecules have a water-loving end and a grease-loving end, so they can lift oil and dirt into water. See…
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Science
Sound
Sound is a vibration that travels through air as a wave. See what pitch and volume mean, why echoes happen…
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Science
Gravity
Gravity is a pull between anything with mass. See why things fall, why orbits are falling sideways, and why…
The World
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The World
Seasons
Seasons come from the tilt of the Earth, not its distance from the Sun. See why days lengthen, why summer is…
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The World
The planets
The eight planets of our Solar System, why some are rocky and some are giant balls of gas, and the rule that…
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The World
Phases of the Moon
The Moon's phases come from seeing its sunlit half from a changing angle. See why the cycle takes 29.5 days…
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The World
The greenhouse effect
The greenhouse effect is gases in the air slowing the escape of heat, keeping Earth about 33 °C warmer. See…
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The World
How volcanoes work
A volcano is where molten rock reaches the surface. See why rock melts, why some eruptions flow and others…
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The World
The water cycle
The water cycle is how the Sun lifts water from the sea and land and rain brings it back. See where rain…
How Things Work
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How Things Work
Electricity
What electricity is, how voltage, current, resistance and power fit together, why a kettle uses more than a…
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How Things Work
Ohm's law
How Ohm's law links voltage, current and resistance in a simple rule, with a worked example you can check…
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How Things Work
Batteries
How a battery makes electricity from a chemical reaction, why some can be recharged, what volts and…
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How Things Work
Power and watts
What a watt is, how power relates to voltage and current, what a kilowatt-hour on your bill means and how to…
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How Things Work
A fridge
How a fridge works by moving heat out with a refrigerant, a compressor and coils, why the back is warm and…
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How Things Work
Household electricity
How household electricity works in the UK: mains voltage, alternating current, the consumer unit, circuit…
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How Things Work
Central heating
How central heating works, from the boiler and pump to radiators, thermostats and valves, and how the main…
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How Things Work
The National Grid
How the National Grid carries electricity from power stations over pylons to your home, why the voltage is so…
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How Things Work
A car engine
How a petrol car engine works through four strokes (intake, compression, power, exhaust) and how pistons turn…
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How Things Work
How a meter works
How an electricity meter measures kilowatt-hours with a spinning disc or electronics, what the numbers mean…
Everyday Life
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Everyday Life
Washing machine
How a washing machine fills, heats, tumbles, rinses and spins, and why detergent and gentle tumbling clean…
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Everyday Life
Charging an electric car
How charging an electric car works: the difference between kW and kWh, how long a charge takes at home and on…
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Everyday Life
Car brakes
How car brakes work: fluid carries your foot's push to each wheel, pads squeeze a disc, and why doubling…
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Everyday Life
Dishwasher
How a dishwasher cleans with spinning spray arms, hot water, detergent, rinse aid and salt, and why you do…
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Everyday Life
Microwave oven
How a microwave oven heats food by making water molecules move, why the edges heat first, and why the door…
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Everyday Life
Tumble dryer
How a tumble dryer dries clothes with warm moving air, the three types (vented, condenser and heat pump), and…
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Everyday Life
Kettle
How an electric kettle boils water in a couple of minutes, how it switches itself off by sensing steam, and…
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Everyday Life
Satnav
How a satnav or phone finds your position from GPS satellites by timing their signals, how it works without…
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Everyday Life
Tyre pressure
Why tyre pressure matters, how the air inside holds up your car, where to find the right pressure, and why it…
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Everyday Life
Solar panels at home
How home solar panels turn daylight into electricity, what an inverter does, why they work in the UK, and…
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Everyday Life
Heat pumps
How a heat pump moves heat from the outside air into your home, gives about three units of heat per unit of…
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Everyday Life
LED bulbs
How LED bulbs make light with very little heat, why you should choose by lumens rather than watts, and what…
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Everyday Life
Smart meters
What a smart meter measures, how it sends readings to your supplier, who sees your data, and why it does not…
Finance
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Finance
Interest
How interest works: the price of borrowing money, why it grows your savings and your debts, and what a rate…
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Finance
Compound interest
How compound interest works: interest on interest, why growth is slow at first and then speeds up, and the…
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Finance
Why interest rates change
Why the Bank of England raises and cuts Bank Rate, how that changes mortgages and savings, and why it takes…
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Finance
Deposit protection
How the FSCS protects UK bank and building society savings: the £120,000 limit, what counts as one firm…
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Finance
Fixed and variable rates
What fixed, tracker and standard variable mortgage rates are, what happens when a fixed deal ends, and why a…
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Finance
How a credit card works
How a UK credit card works: the interest-free period of up to 56 days, why paying only the minimum costs…
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Finance
National Insurance
What UK National Insurance is, how it differs from income tax, who pays it, and how qualifying years build…
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Finance
Why starting early helps
Why money paid into a pension early grows more: time and compound growth, with a worked example of how much…
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Finance
Index funds
What a stock market index such as the FTSE 100 is, how an index fund copies it, why the fees are low, and…
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Finance
Inflation
What inflation is, how the UK measures it, why prices keep rising, who aims to keep it at 2%, and why falling…
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Finance
APR and AER
What APR and AER mean on loans, credit cards and savings accounts, why they differ from the plain interest…
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Finance
What a stock exchange does
What a stock exchange does: where shares are listed, bought and sold, how a company floats, how prices are…
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Finance
How banks work
How a bank works: why your balance is a promise rather than a pile of cash, how banks lend, what stops them…
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Finance
Mortgages
How a repayment mortgage works: what each payment covers, why the first years are mostly interest…
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Finance
Credit scores
What a UK credit score is, how Experian, Equifax and TransUnion work it out, what affects it, and why there…
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Finance
Tax
How UK income tax works: the personal allowance, the tax bands, why only the slice above each threshold is…
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Finance
Pensions
How UK pensions work: the state pension, workplace pensions with automatic enrolment, and personal pensions…
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Finance
Stocks and shares
What a share is, how companies sell them, why share prices rise and fall, what dividends are, and why a good…
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Finance
Where money comes from
Where money comes from: how banks create most money when they lend, what the Bank of England and Royal Mint…
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Finance
Exchange rates
What an exchange rate is, why the pound rises and falls against the euro and dollar, what drives it, and why…
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Finance
Bank transfers
How a UK bank transfer works: why no money physically moves, how Faster Payments, Bacs and CHAPS differ, and…
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Finance
Coins and notes
How UK coins and banknotes are made and why they are hard to forge: the polymer notes, the 12-sided pound…
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Finance
Why prices end in .99
Why shops price things at £2.99: how the left-digit effect makes the price look lower, what research shows…
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Finance
Bitcoin and crypto
What Bitcoin is, how a shared ledger replaces a bank, how new coins are created, why the supply is capped…
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Finance
Why a pound was 240 pennies
Why a pound used to be 240 pennies: the medieval system of pounds, shillings and pence, where £sd comes from…
Technology
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Technology
Artificial intelligence
What AI means today: software that learns patterns from examples instead of following written rules, and…
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Technology
3D printing
How 3D printing works: software slices a design into layers, and a printer melts plastic or hardens resin to…
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Technology
4G vs 5G
What 4G and 5G mean, how 5G uses more frequencies and smaller cells, what it speeds up, and why you may not…
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Technology
Why AI makes things up
Why chatbots sometimes state false things confidently: they predict likely words rather than check facts, and…
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Technology
AM, FM and digital radio
How AM, FM and DAB radio differ, why AM travels furthest, why FM sounds clearer, and how DAB packs several…
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Technology
Binary
What binary is, how ones and zeros can store numbers, text and pictures, and why computers use two digits…
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Technology
Chip and PIN
How the chip on a bank card makes a one-time code for each payment, checks your PIN, and why this beat the…
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Technology
How MP3s and JPEGs shrink
How compression makes files smaller by removing detail your senses will not miss, and the difference between…
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Technology
Data centres
What a data centre is: rows of servers, backup power, cooling and network links, why they use so much…
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Technology
How DNS finds a website
How DNS turns a website name into an IP address, the chain of look-ups it uses, why it is fast, and why a DNS…
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Technology
How GPS works
How the GPS satellite constellation fixes your position, why it needs a view of the sky, what other systems…
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Technology
What the padlock means
What HTTPS and the browser padlock mean: the connection is encrypted and the site is the one named, but the…
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Technology
LCD vs OLED
How LCD screens block a backlight while OLED pixels make their own light, and what that means for black…
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Technology
What megapixels mean
What a megapixel is, how many pixels you need for a screen or a print, and why a bigger number does not…
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Technology
Mesh and range extenders
How Wi-Fi range extenders and mesh systems spread a signal through a big house, why one halves your speed…
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Technology
How noise cancelling works
How active noise cancelling uses a microphone and a mirror-image sound wave to quieten steady background…
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Technology
How search ranks results
How search engines order results: words on the page, links from other sites as votes, and many other signals…
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Technology
How spam filters work
How spam filters score email using sender checks, blocklists, patterns and learning from what you mark as…
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Technology
Fingerprint and face unlock
How fingerprint and face unlock work: a scan becomes a pattern of numbers kept on the phone and compared each…
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Technology
How a chatbot is trained
How a chatbot is trained: it reads vast amounts of text, learns to predict the next word, and is shaped by…
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Technology
Fibre broadband
How fibre broadband sends light through glass to deliver fast internet, and the difference between full fibre…
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Technology
Inkjet vs laser
How inkjet printers fire ink through tiny nozzles and laser printers use static electricity and heated toner…
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Technology
Memory vs storage
The difference between a computer's memory (RAM) and its storage: speed, size, what happens when the power…
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Technology
Password managers
What a password manager does: it keeps long unique passwords in an encrypted vault behind one master…
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Technology
How a phone takes a photo
How a phone camera gets good pictures from a tiny lens and sensor by taking several shots in a row and…
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Technology
How phone masts work
What the panels on a phone mast do, why masts are tall, why each covers a small area, and why a phone prefers…
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Technology
How phone payments work
How paying with a phone works: NFC radio, a stand-in number called a token, and your fingerprint, face or…
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Technology
Satellite TV and internet
How a satellite dish collects a weak signal from a satellite 36,000 km up, why it points at one spot, and how…
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Technology
Why Wi-Fi slows down
Why Wi-Fi gets slow: distance, walls, crowded channels and too many devices sharing the same airtime, and…
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Technology
Touchscreens
How a phone touchscreen finds your finger using a grid of electric fields, why gloves and nails do not work…
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Technology
How video streaming works
What happens when you press play on a streamed video: the request, the nearby server, the first clips, the…
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Technology
How wireless headphones work
How wireless headphones turn Bluetooth data back into sound, why the music is compressed, why there is a…
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Technology
Bluetooth
How Bluetooth uses short-range radio to connect headphones, keyboards and speakers, why pairing is needed…
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Technology
What an IP address is
What an IP address is, how it works like a postal address for data, why your home has one shared by all your…
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Technology
How a neural network learns
How a neural network learns: layers of simple units with adjustable weights, a guess checked against the…
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Technology
What a processor does
What a processor does: it fetches instructions, works out what they mean and carries them out billions of…
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Technology
What a SIM card does
What a SIM card is, how it proves your identity to the mobile network, why you can swap it between phones…
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Technology
Two-factor codes
How two-factor sign-in works: a password plus a code from a text or app, how app codes come from a shared…
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Technology
The cloud
What the cloud is: someone else's computers in a data centre that you reach over the internet, why that is…
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Technology
How a web page reaches you
How a web page is cut into packets, sent by different routes through routers and put back together on your…
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Technology
How a computer works
How a computer works: a processor following instructions, memory for now, storage for later, and software…
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Technology
Undersea cables
How undersea cables carry nearly all international internet traffic, how light in glass fibres carries data…
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Technology
Contactless payments
How contactless cards and phones pay by tapping: a chip powered by the reader, a one-time code for each…
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Technology
Digital cameras
How a digital camera focuses light with a lens onto a sensor made of millions of tiny light meters, and how…
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Technology
Email
How email works: your message passes through mail servers, how an address is read, where messages wait, and…
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Technology
The internet
What the internet is: a worldwide network of networks, how data travels in small packets, and what happens…
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Technology
Mobile phones
How a mobile phone connects to the network through radio masts split into cells, how calls follow you as you…
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Technology
Passwords and encryption
How passwords are stored, why long unique ones matter, and how encryption scrambles information so only the…
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Technology
Printers
How printers work: inkjets fire tiny droplets of ink, lasers use static electricity and heated powder, and 3D…
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Technology
QR codes and barcodes
How barcodes and QR codes store information as patterns, how a scanner reads them, why QR codes survive…
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Technology
Radio and broadcast TV
How radio and Freeview TV are broadcast as waves from a transmitter, how the signal carries sound and…
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Technology
Satellites
What satellites are, how they stay in orbit, the difference between low and geostationary orbits, and what…
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Technology
How a screen makes a picture
How a screen makes a picture from millions of tiny red, green and blue dots, how pixels and refresh rate…
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Technology
Search engines
How a search engine finds pages by following links, builds an index like a book's, and ranks results from its…
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Technology
Hard drives and SSDs
How hard drives use spinning magnetic discs and SSDs use flash chips to store files, why SSDs are faster, and…
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Technology
Streaming and compression
How streaming plays video and music while it arrives, why buffering happens, and how compression makes films…
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Technology
Wi-Fi
How Wi-Fi uses radio waves to carry the internet from your router to your devices, why it has a limited…
History
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History
Dating the past
How scientists work out the age of bones, wood and rocks using radiocarbon dating, tree rings and rock…
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History
Roman roads
How the Romans surveyed and built long straight roads, with layers of stone, a curved surface and ditches…
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History
The calendar
Why a year needs leap days, how the Julian and Gregorian calendars differ, why month names look odd, and how…
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History
Time zones
How time zones came about when railways made local sun time impractical, why Greenwich sets the world's…
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History
The steam engine
How steam engines work, how Newcomen and Watt improved them, and why steam power moved factories away from…
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History
Maps before satellites
How maps were made before satellites, using triangulation, theodolites and chronometers, and how the Ordnance…
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History
The Great Fire of London
How the 1666 Great Fire of London started in a bakery and spread so fast, and how it changed building rules…
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History
The printing press
How Gutenberg's printing press worked in the 1450s, why movable metal type was the real breakthrough, and how…
The Human Body
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The Human Body
Your eyes
How the eye focuses light onto the retina, how rods and cones work, how we see colour, and what colour…
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The Human Body
Your ears
How the ear turns air vibrations into sound through the eardrum, three tiny bones and the cochlea, and how…
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The Human Body
Sleep
What happens during sleep, how the sleep stages and body clock work, why the brain stays active at night and…
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The Human Body
Your lungs
How the lungs move oxygen into the blood and carbon dioxide out, what the diaphragm does, and why carbon…
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The Human Body
Your blood
What blood is made of, what red cells, white cells, platelets and plasma do, why blood looks blue in veins…
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The Human Body
Your immune system
How the immune system fights infection with barriers, fast defences and memory, why a fever happens and how a…
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The Human Body
Digestion
How food is broken down from mouth to stomach to gut, how nutrients reach your blood, how long it takes and…
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The Human Body
Your muscles
How muscles contract by sliding fibres, why they work in pairs, the three types of muscle in the body and…
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The Human Body
How signals travel
How nerve cells carry electrical signals, how messages jump between cells, why reflexes are so fast and what…
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The Human Body
Your kidneys
How the kidneys filter blood, keep what the body needs, produce urine and control water and salt balance, and…
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The Human Body
Your skin
What your skin is made of, how it protects you, cools you and senses touch, how it replaces itself and how a…
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The Human Body
Your bones
What bones are made of, how living bone is constantly renewed, how a broken bone heals in stages and why a…
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The Human Body
Your heart
How the heart's four chambers and valves pump blood to the lungs and body, what makes it beat, what the…