Astrodynamics is beautiful, pervasive, and is arguably the most ancient form of science. I try to convey this and its importance in my class AA279A: Space Mechanics. However, the teaching approach can produce completely opposite results and alienate students. Take the definition of coordinate systems and time scales for example. A teacher could introduce a series of obscure relationships and conversion tables between time scales such as TAI, UTC, UT1, GMST and call it the day. But this would miss the central point: astrodynamics create bridges to reconcile the microscopic (atoms), the macroscopic (stars), and the biological (life). The microscopic is great for controlled uniform measurements, the macroscopic is great for the equations of motion, while the biological is the best for our circadian rhythms.
This is done through the most advanced measurements we can obtain today, from counting the vibrations of atoms, specifically the frequency of electromagnetic radiation emitted when electrons in an atom of Cesium-133 transition between energy levels (AtomicTime) to the measurement of the rotation and tilt of the Earth with respect to distant quasars through Very Long Baseline Interferometry (VLBI), which involves a network of radio telescopes around the world (Sidereal Time).
How simple: mapping the uniform oscillations of atoms to the irregular rotation of the Earth around its own axis with respect to the Sun and distant stars. Let's try to put the motivation and the why at the center!
