Chapter 2 of The Nature of Code, Forces, accumulates forces into acceleration and ends with gravitational attraction and orbital motion. The International Space Station is a body held in a real gravitational orbit.
Chapter 2 ends at orbits on a canvas; I seed the same idea from the live ISS position and let the ground track show what gravitational orbit looks like from the ground.
The page fetches the station’s current latitude and longitude from wheretheiss.at and propagates its ground track: a sinusoid in latitude bounded by the orbital inclination, with longitude advancing as the Earth rotates beneath the orbit. One orbit is compressed to roughly 15 seconds, and the track is reseeded to the live position on each poll. The path shown is the observable trajectory that Chapter 2’s gravitational force produces.
The orbit obeys Newtonian gravitation \(\mathbf{F} = -\frac{GMm}{r^2}\hat{\mathbf{r}}\), giving a period from Kepler’s third law \(T = 2\pi\sqrt{a^3/GM} \approx 92.9\) min. The ground-track latitude is \(\varphi(t) = \arcsin(\sin i \,\sin u)\) with inclination \(i = 51.6^\circ\) and argument of latitude \(u = u_0 + nt\), where the mean motion is \(n = 2\pi/T\). Longitude advances by Earth’s rotation rate \(\omega_E\) relative to the orbital plane, which is why successive passes shift westward.
Data source: wheretheiss.at API
Endpoint:https://api.wheretheiss.at/v1/satellites/25544
Access: Public, no key. Loaded from an hourly server-side refresh when possible, with a bundled snapshot fallback, and a live browser fetch only when the API allows CORS. Data window: Aug 6, 2026 (pulled Aug 6, 2026 UTC)
The ISS position is listed below.