Gravity being the manifestation of the curvature of spacetime can create regions which are inaccessible to a class of observers. An example of such a region is the event horizon of black objects which acts as an one way causal boundary. Interestingly, it is possible to assign thermodynamic properties like temperature, entropy etc. to the event horizon. Horizon thermodynamics is believed to be a crucial input to understand the quantum dynamics of gravity. The basis of this thermodynamic analogy is the second law of black hole mechanics which asserts that the area of the event horizon can not decrease in any classical process. 

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