Tall Bloke is enthusiastic about barycentric orbits – but do they exist? I had visualised the 90,000 plus years cycle of the Sun around its barycentre as perhaps having an association with the Milankovitch 100,000 year cycle, an otherwise small affect and yet the 100,000 year cycle is clearly visible in proxy data such as foraminifera on the sea bed.
It seems the barycentre orbit theory might all be a mirage – see http://malagabay.wordpress.com/2012/11/03/inventions-and-deceptions-bary… … but in the comments Tall Bloke argues his case, but does not necessarily get his way. The theory of the barycentric orbit was devised by Rhodes Fairbridge (see some early posts and links on this subject) but is perhaps adequately explained on Wikipedia (the theory does not attract the thought police so it is alright to read it) – see http://en.wikepedia.org/wiki/Barycentre and provides an adequate overview of the subject, not in terms of Fairbridge but as it is understood today. The appears to start when the Earth's wobble is discussed. It can be interpreted as the Earth rotating around an internal pivot point (the barycentre) or otherwise. For example, it might be a relic of disturbances in the rotation of the Earth and have nothing whatsoever to do with a hypothetical barycentre.