Rocks in Space
A teaching model in scaled units — not a precision integrator. Built by John Rachlin, Khoury College of Computer Sciences. Research & development — not peer-reviewed.
The Earth–Moon system is much wider than it is tall. Turn the phone sideways to see the whole Hill sphere.
A three-body model of the Earth–Moon system with solar tidal forcing.
An interactive model in scaled units. It shows why the temporary capture of a near-Earth asteroid is possible, and how fragile it is. It is not a precision integrator and will not reproduce any specific object's trajectory.
The default view looks down from ecliptic north, so the Moon and the Sun both circle counterclockwise — the direction the real ones do. The white circle is the Moon's path about the Earth–Moon barycenter; the faint sphere is the Hill sphere, the region where Earth's gravity wins over the Sun's.
Lengths are scaled, but time is anchored to the real system: the Moon's period in the model is 27.32166 days and the Sun comes round in exactly 365.25636 days. The elapsed-years readout counts that same year.
2024 PT5 was bound to Earth for about two months in 2024. Captures like it are brief and end the same way they began — the Sun pulls the object away again. Read about real captures →