Ah, thanks, I thought I’d read that it was outside, but didn’t feel like doing the math to confirm in that second. I’ll edit it!
E: Ah, I have figured out what it was: the Sun-Jupiter barycentre is outside the surface of the sun, and that’s why the Barycentre is a bad metric. Different argument.
The Earth-Moon barycenter is below the surface of Earth, not outside Earth’s body.
https://en.wikipedia.org/wiki/Barycenter_(astronomy)
Ah, thanks, I thought I’d read that it was outside, but didn’t feel like doing the math to confirm in that second. I’ll edit it!
E: Ah, I have figured out what it was: the Sun-Jupiter barycentre is outside the surface of the sun, and that’s why the Barycentre is a bad metric. Different argument.