The paper explains why the physics involved in atmospheric and sub-surface heat transfer appears to have been misunderstood, and incorrectly applied, when postulating that a radiative “greenhouse effect” is responsible for warming the surfaces of planets such as Venus and our own Earth.A detailed discussion of the application of the Second Law of Thermodynamics endeavours to settle the much debated issue as to whether or not a thermal gradient evolves spontaneously in still air in a gravitational field. The author is aware of attempted rebuttals of this hypothesis, but cogent counter arguments are presented, together with reference to empirical evidence.The ramifications are substantial, in that they eliminate any need for any “greenhouse” explanation as to why the surface temperatures are as observed. No other valid reason appears plausible to explain how the required energy gets into the planetary surfaces, this being especially obvious in regard to the high temperatures measured at the surface of the crust of Venus.The paper includes some counter-intuitive concepts which sceptical readers may be tempted to reject out of hand. Physics sometimes has some surprises, and so you are encouraged to read and understand the argument step by step, for it is based on sound physics, and unlocks some mysteries of the Solar System, including core and mantle temperatures, not previously explained in this manner to the best of the author's knowledge.