What is the law of conservation of energy?

Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. In the case of a closed system, the principle says that the total amount of energy within the system can only be changed through energy entering or leaving the system. Special relativity shows that mass is related to energy and vice versa by E = mc², the equation representing mass–energy equivalence, and science now takes the view that mass-energy as a whole is conserved. This implies that mass can be converted to energy, and vice versa.

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