Hank G ☑️ on Nostr: Right the joke is about the barycenter about which two objects orbit each other. It ...

Right the joke is about the barycenter about which two objects orbit each other. It gets even more complicated when you remember that these aren't point masses orbiting each other. So the elliptical approximation of the orbit is for one instant in time, even if we are just accounting for gravity and no other forces. What you end up with when you view the state in terms is an osculating element set over time. If you graph the terms you'll see a larger trend in the orbit state and a much faster oscillating looking component along the the curve as well. The barycenter is constantly changing as well. For systems with very large mass discrepancies, say a man-made satellite around the earth, you can essentially say it is the center of the larger mass.