Hi
Does the earth’s annual wobble have a scientific name?
Websites refer to the Chandler wobble (14 months/433 days ) and annual wobble. They’re not the same. I have not seen a scientific name for the annual wobble. Could it be called a nutation or precession/axial precession? Not sure.
I look forward to your feedback.
Nutation is the overall combined motion. One body has one nutation, each component is not “a” nutation. The annual wobble is just a component of Earth’s nutation, and I know of no better term for it than “component of nutation”
It’s definitely not precession, that’s referring to the kilo-year-timescale changes (although both are just orders-of-magnitude variant parts of the same motion).
I’ve seen references to ‘annual nutations’ online. Are these just aggregate quantities of combined motions?
Yep - people vary their terminology, and there’s no overall nutation-terminology-police. You have to realise, there are something like 160 terms just to the standard nutation theory which is, I think, still the 1980 IAU theory (there’s a 2000 precession-nutation theory as well, but not sure what it covers, haven’t touched this stuff since 1991 or so) so it’a all aggregate
I should also add - I never learned this stuff in the one intro-to-astronomy course I took, I learned it in geophysics, since core-mantle movement is a component of nutation.
Thanks MrDibble. Very helpful
Can you give more detail on what you think you’re referring to by “annual wobble”?
That is a good question, since a glib answer would be that it is the component with period 365.2 days, but there is a lot more than one sole effect driving that frequency.
To be more explicit, I am not sure the OP isn’t referring to the baseline 23-ish degree axial tilt and mis-describing that as a wobble.
I was thinking of some of the more esoteric reasons for the Earth’s wobble … non-uniform density for example … and came upon a table in a scientific paper’s introduction … “Assessment of the effect of three-dimensional mantle density heterogeneity on Earth rotation in tidal frequencies” and scroll down to Table 1 …
That’s a lot of factors to consider …
This is how I have seen the term being used:
“tidal oscillations in the coupled atmosphere–ocean system induce small perturbations of Earth’s prograde annual nutation, but matching geophysical model estimates of this Sun-synchronous rotation signal with the observed effect in geodetic Very Long Baseline Interferometry (VLBI) data has thus far been elusive”