Summary Use spirograph art to model how orbits go through precession (the orbit slowly rotates around the central body). Lessons activity is in Forces in Space Materials spirograph set ballpoint pens paper Procedure We usually think of the orbit of a body in space to be fixed, but 'apsidal precession' of orbits (slow rotation of the orbit path) has been observed - see image here: https://en.wikipedia.org/wiki/Apsidal_precession#/media/File:Perihelion… Most planets in the solar system have apsidal precession, but at a very slow rate, so their orbits are almost stationary.https://en.wikipedia.org/wiki/Apsidal_precession Show students orbit precession images. Note that drawings of precession are highly exaggerated - the actual shift on each orbit is very small and only observed after watching an orbiting body for many years. Lunar precession of the Moon around Earth image: https://en.wikipedia.org/wiki/Lunar_precession#/media/File:Moon_apsidal… Also animations of lunar precession at https://en.wikipedia.org/wiki/Lunar_precession A star, called S2, orbiting Sagittarius A* (the black hole at the centre of the Milky Way) has been observed for 27 years to notice precession: https://newatlas.com/space/star-s2-spirograph-orbit-supermassive-black-… Students make art with a spirograph to model the patterns made by precession of orbiting bodies. Grades taught Gr 4 Gr 5 Gr 6
