Ascientific theoryis an explanation of an aspect of thenaturalworld that can berepeatedly testedand verified in accordance with thescientific method, using acceptedprotocolsofobservation, measurement, and evaluation of results. Where possible, theories are tested under controlled conditions in anexperiment.[1][2]In circumstances not amenable to experimental testing, theories are evaluated through principles ofabductive reasoning. Established scientific theories have withstood rigorous scrutiny and embody scientificknowledge.[3]