subject
Physics
How physical systems are modeled, where the models break, and how physicists choose between competing accounts of the same phenomenon.
7 lessons in physics
Classical and Quantum: When Each Description Breaks Down
A baseball arcing toward the outfield and an electron drifting through a copper wire are both, in some ultimate sense, governed by the same physics.
4 min · comparison
How Gravity Curves Spacetime
Drop a coin and a feather in a vacuum chamber and they fall together.
4 min · deepening
How Light Behaves as Both Wave and Particle
Shine a laser through two narrow slits in a card and look at the wall behind it.
4 min · foundation
What Energy Conservation Actually Says
Drop a ball. It falls, it bounces, it bounces lower, and eventually it stops. A student who has just learned that energy is conserved might pause here. Where did the energy go? The ball had gravitatio…
4 min · foundation
Why Entropy Defines the Arrow of Time
Drop a sugar cube into hot tea and it dissolves. Film the dissolution and run the film backward, and you see something no one has ever witnessed: dispersed sugar molecules gathering themselves into a …
3 min · deepening
Why the Standard Model Has Three Generations of Particles
Almost everything you have ever touched is built from just four particles: the up quark, the down quark, the electron, and the electron neutrino.
4 min · synthesis
Why Time Slows Down at High Speed
Imagine you are on a train gliding past a station at enormous speed, and you bounce a pulse of light straight up from the floor of your car to a mirror on the ceiling and back down.
4 min · foundation