About the game
Worldline is a science game about special relativity where you fly right across a Minkowski spacetime diagram. Time flows from bottom to top, your path is drawn as a line, and light always travels at 45°.
The diagram shows your light cone (where you can still get to), your line of simultaneity (it tilts with your speed) and dots on your worldline — the seconds of your own clock. At speed they come less often: proper time is the “length” of a worldline, dτ = dt·√(1 − v²/c²).
Every 32 seconds you must return to your twin — and see the twin paradox for yourself. Beacons teach the relativity of simultaneity and supernova flashes the Doppler effect: you can’t outrun light, but if you run away it arrives redshifted and weak. Play free in the browser on desktop and mobile.
Tips
- ›Sparks outside the bright wedge are out of reach — don’t waste time on them.
- ›Watch the green meeting cone: once you leave it, you can no longer make it back to your twin.
- ›Fly far, fast, and come back — you will age less than your twin and earn a bigger bonus.
- ›For beacons A and B, speed up until the blue “now” line is parallel to the A–B line.
- ›Run away from a supernova: the faster you flee, the weaker the radiation.
FAQ
- What is a worldline?
- The path of an object through spacetime. A Minkowski diagram puts distance across and time up. A body at rest draws a vertical line, light a 45° line.
- What is a light cone?
- All the events you can reach without moving faster than light. Events outside the cone can neither be reached nor influenced.
- What is the twin paradox?
- A twin who flies away and comes back is younger than the one who stayed. The diagram shows why: a straight worldline is “longer” in proper time than a bent one.
- Why is simultaneity relative?
- Events are simultaneous for the observer whose “now” line passes through both. The tilt of that line depends on speed, so different observers disagree on what happened first.