The FREE online science and technology book

Want to know how your earbuds make music, how telephones squeeze sounds down wires, why broadband is faster than dialup, or how science can make you happy? You've come to the right place!

Hard stuff... made simple!

Explain that Stuff is an online book of around 450 easy-to-understand articles (plus around 2000 photos and 450 illustrations), covering how things work, cutting-edge science, cool gadgets, and computers. There's more information on this website than in your average expensive science book—and it's all completely free to use!

Read it as we write it

We're adding new articles all the time, so do keep popping back! If you use RSS, you can use our articles feed to find out about new pages as soon as we publish them.

Most read

These are our top-ten most-read articles:

1. Water pollution: Rivers and seas take a long time to recover from the effects of careless human treatment. What causes pollution and what can we do to stop it?
2. Magnetism: One of the first bits of science people studied, magnetism is still just as relevant today in everything from electric cars to body scans at the hospital.
3. Electricity: The most versatile and useful form of energy in our world, electricity is going to become a whole lot more important in future.
4. Global warming: Why is the world getting hotter and what can we do about it? What will be the consequences for humankind and the rest of the living world?
5. Air pollution: It's often invisible, but air pollution can be just as damaging as water pollution and sometimes travels much further. Doing a school or college project on pollution? Here's a comprehensive list of resources to help you get started.
6. Electric motors: These amazing machines turn electricity and magnetism into movement, powering everything from handheld toothbrushes to bikes, cars, and trains.
7. Heat insulation: Why pay a fortune to heat your home if the energy you burn is simply escaping into the air? What can you do to stop it?
8. Energy: You can't see it, smell it, or touch it, but you can't do anything without it! Where does the world's energy come from? Are we about to run out?
9. Batteries: We all need electricity, wherever we happen to be, so thank goodness for batteries—miniature power plants you can carry in your pocket!
10. Steam engines: Coal and water used to power our world. Find out why steam engines were so amazing and why modern engines are even better!

More popular articles...

What else is on our site?

The hundreds of detailed articles on our site are divided up into a number of broad topical areas, which we've listed below. We've also given you a rough idea of the kind of intriguing questions you're going to find answers to in each section!

• Communications: Can you really make light bend round corners? How can you make sound invisible with a directional loudspeaker?
• Computers: How can you make a computer think like a human brain or cause climate change inside your PC? Who invented the computer—and why on Earth did it take them so long?
• Electricity and electronics: How can you make coffee with a stream of electrons? How can magnets detect burglars in your home?
• Energy: How does wind energy come from the Sun? Is nuclear power safe or not?
• Engineering: What stops a bridge falling over? How come a person can lift more stuff with a crane than with their bare hands?
• Environment: Can we still stop dangerous climate change? What causes air and water pollution and how can the world clean up its act?
• Gadgets: How does a flash memory card store your holiday snaps? Why can a synthesizer mimic any musical instrument that's ever been invented (and even ones that haven't been)?
• Home life: How can you make windows turn dark at the flick of a switch? How does an artificial leg work? If an energy-saving lamp saves energy, how come it still makes exactly the same amount of light?
• Instruments and measurements: How can we measure the speed of a tornado or detect dangerous radioactivity? How does an iris scanner recognize your eyes?
• Leisure: Why does a piano sound different from a violin? Where's the best place to sit on a rollercoaster if you want to scare yourself to death?
• Materials: If you had a piece of platinum as big as a man, how much would it be worth? Why doesn't a dry-stone wall fall over? Is it true that glass is a kind of liquid?
• Science: Which part of a candle flame is the hottest? Why does chocolate actually taste good? How can science help us solve crimes?
• Tools and equipment: Why don't fireproof clothes catch fire? How come you can lift the tailgate of a car with one finger when it's made of thick and heavy glass? Can a robot really learn to play drums?
• Transportation: If a man can't fly, how can a plane fly if it weighs as much as 5000 men? How come we say a wheel reduces friction if it's got a tire that grips the road?