The Intrinsic Heat Flow Contrast Between Uranus and Neptune

This paper examines the striking difference in internal heat escaping from Uranus and Neptune. Using only published input values and transparent formulae, the calculation addresses how large the contrast is in total power, not only in flux per unit area, and how it compares with the sunlight each planet receives. The headline results are: intrinsic_flux_W_m2_uranus = 0.042; intrinsic_flux_W_m2_neptune = 0.433; flux_ratio_neptune_to_uranus = 10.31. The method, inputs and limitations are stated in full so that any reader can reproduce or rescale every number from the deposited calculation script. The central finding is that in total power the contrast is slightly smaller than in flux because Uranus is the larger planet, but it remains close to an order of magnitude, so any successful interior theory must let one planet retain or release heat far more effectively than its near-twin. Agreement and disagreement with independent published estimates are reported at their actual size, and the conclusions are limited to what the budget arithmetic supports.