# Does the earth's annual wobble have a scientific name? **URL:** \ **Category:** Factual Questions\ **Created:** [November 10, 2017, 8:42am UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206 "2017-11-10T08:42:01Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![davidmich](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@davidmich](https://boards.straightdope.com/u/davidmich)\ **Post date:** [November 10, 2017, 8:42am UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/1 "2017-11-10T08:42:01Z")
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. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [November 10, 2017, 10:30am UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/2 "2017-11-10T10:30:06Z")
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). ---
**Author:** ![davidmich](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@davidmich](https://boards.straightdope.com/u/davidmich)\ **Post date:** [November 10, 2017, 10:36am UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/3 "2017-11-10T10:36:20Z")
> [@MrDibble](#): > > 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? ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [November 10, 2017, 11:34am UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/4 "2017-11-10T11:34:04Z")
> [@davidmich](#): > > 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 ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [November 10, 2017, 11:39am UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/5 "2017-11-10T11:39:52Z")
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. ---
**Author:** ![davidmich](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@davidmich](https://boards.straightdope.com/u/davidmich)\ **Post date:** [November 10, 2017, 12:55pm UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/6 "2017-11-10T12:55:12Z")
> [@MrDibble](#): > > 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 ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [November 11, 2017, 1:15pm UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/7 "2017-11-11T13:15:35Z")
Can you give more detail on what you think you’re referring to by “annual wobble”? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [November 11, 2017, 1:45pm UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/8 "2017-11-11T13:45:38Z")
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. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [November 11, 2017, 1:57pm UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/9 "2017-11-11T13:57:54Z")
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. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [November 11, 2017, 2:33pm UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/10 "2017-11-11T14:33:49Z")
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”](http://www.sciencedirect.com/science/article/pii/S167498471630132X) and scroll down to Table 1 … That’s a lot of factors to consider … ---
**Author:** ![davidmich](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@davidmich](https://boards.straightdope.com/u/davidmich)\ **Post date:** [November 12, 2017, 2:24pm UTC](https://boards.straightdope.com/t/does-the-earths-annual-wobble-have-a-scientific-name/801206/11 "2017-11-12T14:24:34Z")
> [@LSLGuy](#): > > Can you give more detail on what you think you’re referring to by “annual wobble”? > **[The Global S $$\_1$$ 1 Tide in Earth’s Nutation - Surveys in Geophysics](https://link.springer.com/article/10.1007/s10712-016-9365-3)** > > Diurnal S $$\_1$$ 1 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... 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”