2. Thermal Evolution Models

The study of Earth as an object whose history can be understood by application of physical laws dates back 200 years. This tradition is, however, rife with missteps related to as yet undiscovered physics or fundamentally incorrect assumptions. While the former is unavoidable, the latter amounts to self-inflicted wounds that may have forestalled scientific progress. Even in the absence of knowledge of initial conditions, linear mathematical relationships such as first order loss (e.g., radioactive decay) have proved useful in predicting Hadean conditions. However, more complex physical systems cannot be uniquely extrapolated back in time. For example, mantle convection, a highly non-linear, dispersive, chaotic system is, by its very nature, uninvertible. This fact has not inhibited generations of modeler’s from making ab initio predictions regarding early Earth evolution. Their results were initially limited by technological impediments and adoption of assumptions regarding the relationship between interior temperature and planetary heat loss that narrowed possible solutions. Radically new proposals regarding both the latter issue and discontinuous transitions between modes of heat loss have tempered earlier conclusions that plate-tectonic-like behavior could not arise on early Earth. Physical calculations have an important role to play in assessing the plausibility of Hadean geodynamic models, but should best be seen as “convenient fictions”.