Why the Universe Works
The rules everything obeys Why Things Move · Energy Never Dies · Light & Waves · The One Force · Space, Time & Gravity · The Quantum World. The same handful of laws runs a falling apple, a phone screen and a distant galaxy — physics is the universe's source code, and it's the same everywhere.
Ages 14–16
What's inside
Why Things Move — forces, motion and Newton
Push a shopping trolley and it rolls; stop pushing and it slows and stops. For two thousand years people thought that was the natural rule: things need a constant push to keep moving. It's wrong, and seeing why is the beginning of all physics. The trolley stops because of a hidden force — friction — not because moving is unnatural. Out in space, with nothing to rub against, a nudge lasts forever.
Energy Never Dies — conservation and heat
Energy is the currency of the universe — the thing that lets anything happen. It comes in forms you can swap between: movement, height, heat, light, sound, chemical, electrical, nuclear. The single deepest law in all of science is that the total never changes: you can't make energy from nothing or destroy it, only convert it. A battery doesn't 'contain electricity' — it holds chemical energy waiting to become electrical, then light and heat.
Light & Waves — the spectrum you can't see
A wave is a clever trick: it moves energy from place to place without moving the stuff it travels through. Drop a stone in a pond and the ripple races outward, but a floating leaf just bobs up and down — the water didn't travel, the pattern did. Sound is a wave in air, light is a wave in the electric and magnetic fields that fill all space, and the difference between a radio signal and a deadly X-ray is only how big the ripples are.
The One Force — electricity and magnetism, joined
Rub a balloon on your hair and it sticks to the wall; a fridge magnet clings without any wire. For centuries these looked like two separate mysteries — sparks and lodestones. Then, in a handful of experiments in the 1800s, people found they're bound together: electricity and magnetism are a single force wearing two masks. That link is the machinery behind every motor, generator and radio signal on the planet.
Space, Time & Gravity — Einstein bends the rules
Newton's universe had one master clock ticking the same for everyone, and space was a fixed empty stage. Einstein tore up both ideas. He started from one stubborn fact: light always travels at the same speed, no matter how fast you chase it. Follow that to its logical end and something has to give — and what gives is time and space themselves. They're not the fixed backdrop; they stretch and bend depending on how you move and where you are.
The Quantum World — the strange rules of the very small
Everything you've read so far — motion, energy, waves, relativity — is the physics of the big and the fast. Zoom down to atoms and their parts, and the rulebook is thrown out and rewritten into something genuinely weird. Down there, energy comes in tiny fixed lumps ('quanta'), a single particle can be in a blur of places at once, and simply looking at it changes what it does. It sounds like fantasy. It is the most precisely tested theory in the history of science.
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