To answer your questions as best I can: The results were data, not theory. Secondly, there is merit for tectonic movement, but based only on some differential heat, Imo. Thirdly, if the crust is resting on a flowable interface, then not much heat should be generated. Fourth, I suspect there are possible sources of heat such as radio-activity, or a slow process of cooling after first formation, and certain chemical processes still going on, or a combination of all of the above. And there may be more that can be added. We do not know for sure yet.<br /><br />I think the article said the rotation period of the interior was slightly slower than the crust, but my memory is sometimes likewise.<br /><br />Imo, your last question is more tenuous in terms of answer. We do not know very much yet in these areas. The sun may play a major role in this, but on the other hand there are influences going on here on earth that require a lot more understanding. Hopefully science can answer some of these questions with time and intent in the future to investigate.<br /><br />Let me ask you, how does magnetic pole switching affect our environment? And does it play a role in the age of the surface as opposed to the interior?<br />