We do not feel the searing heat beneath our feet as we are shielded by our planets crust but it does have a significant impact on our lives. Nuclear reactions in the earth core generate the energy that heats up the surrounding material of the core. The heat transfer reduces the density of this material, which then moves upwards towards the crust. But there, it starts to lose heat and cool down, so its density increases again, so that it sinks down to the centre of the Earth. This circular motion of matter is a convection process that moves the very ground we live on.

Heat can also be conducted or transferred via radiation. No matter what type of heat transfer we encounter, it is always subject to the second law of thermodynamics.

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