The FREE online science and technology book
Want to know why giant ships can float, how your earbuds make music, what graphene is, or how windows can clean themselves? You've come to the right place! Here you'll find simple explanations you can really understand—hurrah!
Hard stuff... made simple!
Explain that Stuff is an online book written by science writer Chris Woodford (author of many popular science books for adults and children). It includes over 400 easy-to-understand articles, richly illustrated with clear artworks and animations, covering how things work, cutting-edge science, cool gadgets, and computers. We take the "pain" from explain and the "tough" out of stuff! There's more information on this website than in your average expensive science book, it's continually updated, and it's completely free to use! Explain that Stuff also helps to support curriculum learning (conventional STEM education and home-schooling).
How to use this site
There are five simple ways to find what you want:
A-Z index: Browse articles by name, from accelerometers to zeolites... via induction motors, LCDs, and regenerative brakes.
Timeline: Find inventions by date, from the prehistoric birth of solar energy to the development of quantum computers.
Random: Discover something new. Keep hitting "random" till you find something you like.
Search: Use our safe, Google-powered search engine.
Teaching guide: Browse a typical school curriculum to match articles from this site to topics you want to study or teach.
What's hot in June 2022?
In the news now...
Catching and bringing CO2 back down to ground sounds like a great idea, but a new poll of experts concludes it's no "magic bullet" for reaching net zero emissions. What exactly would it involve and how much difference could it make?
With new advances in data teleportation (sending quantum information between networked machines), is the age of quantum computing about to arrive?
As fears grow about the security of the world's natural gas supply, interest is once again turning to hydrogen—potentially a cleaner way to replace fossil fuels burned in trucks, ships, and planes.
There's a new plan to catch spent boosters from space rockets as they fall back to Earth... using carefully piloted helicopters! Maybe it's a good time to remind ourselves how helicopters stay in the air and how they differ from conventional airplanes.
Over at Kennedy Space Center in Florida, NASA has rolled out its giant new Moon-ready rocket, the Space Launch System (SLS). It's the culmination of almost 3000 years of rocket technology, as you can discover in our ever-popular overview.
What's new for '22?
We have a few brand new articles on the site... and more to come in the next few months:
Can we imagine a world where computers are smart enough not to need us? Is "human intelligence" a good starting point for designing useful machines?
It's taken over two millenia for people to understand how gravity holds the universe together. What do we know so far about this most mysterious of forces?
Planes can trace their history back thousands of years to ancient myths and legends. Why have humans always dreamed of soaring to the sky... and why did it take us so long?
The science behind cranes is easy to understand, but why are there so many different types? How much can they lift... and what stops them toppling over?
Electricity is an ancient science that powers our modern world. Why did it take so long to figure out how it works and put it to practical use? Find out in our sparky story of electric power!
Computers are wonderful machines you can reprogram to do almost anything. Learn more about algorithms, computer languages, and the basic principles of coding in our simple guide.
It's no big surprise that other people aren't quite what they seem. But the astonishing finding from modern psychology is that even our own minds are strange and complex things we don't fully understand.
From atoms and cells to nuclear power plants and the human brain, the scope of science is truly amazing. But what exactly is the scientific method... and why is it still our best hope for making sense of the world?
How did we get from the alphabet to the Internet in about three to four thousand years?
These are some more of our classic, ever-popular articles:
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?
The most versatile and useful form of energy in our world, electricity is going to become a whole lot more important in future.
Can we build a brave new world just by shuffling atoms and molecules under a microscope?
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.
Wheels with teeth carved around them can make you go faster or bump up your power—and here's how.
We all need electricity, wherever we happen to be, so thank goodness for batteries—miniature power plants you can carry in your pocket.
These amazing machines turn electricity and magnetism into movement, powering everything from handheld toothbrushes to bikes, cars, and trains.
Climate scientists recently issued their strongest ever warning about the growing risks of irreversible "global warming." If you find the subject baffling, try our easy-to-follow introduction.
Why buy yourself an expensive computer or programs to go with it when you can get access to something just as good over the Internet? What are the benefits and drawbacks of working in "the cloud"?
What else is on our site?
The articles on our site are divided up into broad topical areas, listed below. We've also given you a rough idea of the kind of questions you're going to find answers to in each section:
Why do we bounce telephone calls off satellites? How do cellphones work? What's the difference between digital radio and ordinary radio?
How can you make a computer think like a human brain? Who invented the computer—and why on Earth did it take them so long?
What's the difference between "electric" and "electronic"? How can you make coffee with a stream of electrons? How can magnets detect burglars in your home?
How does wind energy come from the Sun? Is nuclear power safe or not? Will the world ever run out of energy? Why are we still so dependent on "fossil fuels"?
What stops a bridge falling over? Why can a person lift more stuff with a crane than with their bare hands? What's the difference between hydraulics and pneumatics and why would you use one instead of the other?
Can we still stop dangerous climate change? What causes air and water pollution and how can the world clean up its act? Is organic food really "better"—and, if so, why?
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)?
How can you make windows turn dark at the flick of a switch? If an energy-saving lamp saves energy, how come it still makes exactly the same amount of light?
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?
Which part of a candle flame is the hottest? Why does chocolate actually taste good? Where's the best place to sit on a rollercoaster if you want to scare yourself to death?
How does an iris scanner recognize your eyes? Why don't fireproof clothes catch fire? Can a robot really learn to play drums?
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? Why do huge ships float when even tiny bits of metal sink?
Who uses this site?
In the 16 years we've been online (as of April 2022), pages from this site have been viewed over 125 million times in total. Our articles have been cited by dozens of books and over 1750 academic papers. We've received almost 4000 user feedback forms in the last decade and 92% gave us four or five stars out of five—but there's always plenty of room to do better. We hope you find this site useful too!
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