I Don't Get to Say 'It's Just Magic'
One of my kids, eight years old, asked why things get smaller when they walk away. Nineteen interactive, physically accurate relativity drills later — starring Liza, Vika, and George — here's what came of refusing to hand-wave.
One of my kids — eight years old, the age where “why” is a weapon — wanted to know why things get smaller when they walk away from you.
Not look smaller. Smaller. And the honest engineer’s answer is: they don’t. Nothing shrinks. Your eye measures the angle a thing carves out of your field of view, not the thing itself. Walk away and the angle collapses; the person stays exactly the size they were. That’s a real answer, and it happens to be the first rung of a ladder that ends, if you keep climbing, at Einstein.
I have a rule with my kids. I don’t get to say “it’s just the way it is,” and I don’t get to say “it’s magic.” Those are the two phrases that quietly kill a curious mind, and I’d rather stay up too late drawing light rays on the back of a receipt than reach for either one.
So the bedtime question turned into a project.
Nineteen drills, two settings
It’s now a series of interactive, physically accurate relativity drills — nineteen of them — starring my three kids, Liza, Vika, and George. They run from “what does ‘moving’ even mean?” through the lightning train and the collapse of a universal “now,” time dilation, length contraction, the twin paradox, all the way out to how GPS satellites literally correct for relativity — because if they didn’t, your phone’s idea of where you are would drift off by kilometers a day.
Every drill has two settings: “explain it for a kid” — names, plain words, pictures — and the full math one click away. Same simulation running underneath both. The physics is accurate, not merely illustrative. So it works for the eight-year-old who asked the question, and equally for the adult who nodded through relativity in school and never actually bought it.
The series is live at Theory of Relativity.
It is not finished, and it never really will be, because the QA team is three small, relentless, deeply unimpressed minds who keep finding the holes I left. Which is the whole point. I didn’t build this to teach them relativity. I built it because they wouldn’t let me get away with “it’s magic,” and they were right not to.