The Mudcat Café TM
Thread #170768   Message #4135334
Posted By: Steve Shaw
05-Feb-22 - 10:42 AM
Thread Name: BS: SPACE - James Webb Telescope LAUNCH-Dec 2021
Subject: RE: BS: SPACE - James Webb Telescope LAUNCH
The centre of mass of the earth-moon system is 1058 miles inside the earth measured from the surface, whereas the centre of the core is 3958 miles down. I think it would be true to say that all pairs of bodies, in which one appears to be in orbit around the other, follow the rule that they both actually "orbit" around their centre of mass. In the case of the telescope and the point L2, there isn't a centre of mass because L2 hasn't got mass. That's why the wiki article states that the halo "orbit" isn't an orbit in the usual sense. But a physics thickie such as meself is perfectly happy, for sheer convenience, to talk about it as if it was.