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Core physics concepts, tagged as beginner, intermediate, or advanced so you can find content that matches where you're at.
Antimatter: The Universe's Missing Mirror Image
Every particle of matter has an opposite twin — and when they meet, both vanish in a flash of pure energy.
intermediateConceptBlack Holes: Where Gravity Wins
How a star can collapse into something so dense that not even light escapes.
intermediateActivityCircuits: Current, Voltage, and Resistance
Three quantities, one equation, and you can explain how every electronic device in your house works.
beginnerActivityCircular Motion: Why Turning Always Means Accelerating
You don't have to speed up or slow down to be accelerating — you just have to change direction.
advancedConceptDark Matter and Dark Energy: The 95% of the Universe We Can't See
Ordinary matter — everything you've ever touched or seen — makes up only a small slice of what the universe is actually made of.
intermediateActivityElectric Fields and Coulomb's Law
Charged objects push and pull on each other without touching — here's the rulebook for exactly how.
beginnerActivityEnergy and Work
What physicists actually mean by 'energy' and 'work' — and how they're connected.
advancedActivityInterference and Diffraction: The Wave Nature of Light
Why soap bubbles show rainbow swirls, and why light bends around edges instead of casting perfectly sharp shadows.
beginnerConceptKinematics: Describing Motion
Before you can explain why things move, you need the vocabulary to describe how they move.
intermediateActivityMagnetism and Electromagnetic Induction
Electricity and magnetism aren't two separate topics — they're the same force, viewed from different angles.
beginnerActivityMomentum and Collisions
Why a loaded truck is so much harder to stop than a bike — and what really happens when things crash.
beginnerActivityNewton's Laws of Motion
The three rules that describe how and why objects move the way they do.
beginnerActivityProjectile Motion: Why Everything Thrown Follows a Curve
A thrown ball, a kicked football, and a launched water balloon all trace out the exact same shape — here's why.
advancedConceptQuantum Entanglement: 'Spooky Action at a Distance'
Two particles can become linked so completely that measuring one instantly tells you about the other — no matter how far apart they are.
advancedConceptQuantum Superposition
How particles can be in multiple states at once — until you measure them.
advancedConceptQuantum Tunneling: Passing Through Walls You 'Shouldn't' Be Able To
Classically, a ball without enough energy just bounces off a barrier. Quantum mechanically, it sometimes gets through anyway.
intermediateConceptRotational Motion and Torque
Everything you learned about motion in a straight line has a spinning equivalent — here's the translation guide.
intermediateActivitySimple Harmonic Motion: Springs, Pendulums, and Repetition
A huge number of physical systems, from guitar strings to atoms, all oscillate according to the exact same math.
intermediateConceptSpecial Relativity: Why Time Isn't Fixed
Einstein's 1905 theory that shows time and space aren't the same for everyone.
advancedConceptString Theory: Physics' Most Famous Unproven Idea
A candidate for uniting gravity with quantum mechanics — genuinely elegant math, but still without direct experimental evidence.
advancedConceptThe Heisenberg Uncertainty Principle
It's not that we lack good enough instruments — some pairs of properties genuinely cannot both be known precisely, ever.
intermediateActivityThermodynamics: The Laws That Govern Heat and Energy
You can't win, you can't break even, and you can't get out of the game — the three laws of thermodynamics, roughly.
beginnerConceptTypes of Forces You Actually Deal With Every Day
Gravity gets all the attention, but friction, tension, and the normal force are doing just as much work.