<Tr> <Td> Müller et al . </Td> <Td> 2007 </Td> <Td> See Herrmann et al. (2005) and Stanwix et al. (2006). Data of both groups collected between 2004--2006 are combined and further analyzed . Since the experiments are located at difference continents, at Berlin and Perth respectively, the effects of both the rotation of the devices themselves and the rotation of Earth could be studied . </Td> </Tr> <Tr> <Td> Eisele et al . </Td> <Td> 2009 </Td> <Td> The frequencies of a pair of orthogonal oriented optical standing wave cavities are compared . The cavities were interrogated by a Nd: YAG laser . Data between 2007--2008 was analyzed . </Td> <Td> ≲ 10 − 17 (\ displaystyle \ lesssim 10 ^ (- 17)) </Td> </Tr> <Tr> <Td> Herrmann et al . </Td> <Td> 2009 </Td> <Td> Similar to Herrmann et al. (2005). The frequencies of a pair of rotating, orthogonal optical Fabry--Pérot resonators are compared . The frequencies of two Nd: YAG lasers are stabilized to resonances of these resonators . </Td> </Tr> <P> Examples of other experiments not based on the Michelson--Morley principle, i.e. non-optical isotropy tests achieving an even higher level of precision, are Clock comparison or Hughes--Drever experiments . In Drever's 1961 experiment, Li nuclei in the ground state, which has total angular momentum J = 3 / 2, were split into four equally spaced levels by a magnetic field . Each transition between a pair of adjacent levels should emit a photon of equal frequency, resulting in a single, sharp spectral line . However, since the nuclear wave functions for different M have different orientations in space relative to the magnetic field, any orientation dependence, whether from an aether wind or from a dependence on the large - scale distribution of mass in space (see Mach's principle), would perturb the energy spacings between the four levels, resulting in an anomalous broadening or splitting of the line . No such broadening was observed . Modern repeats of this kind of experiment have provided some of the most accurate confirmations of the principle of Lorentz invariance . </P>

Discuss michelson morley experiment in detail and explain its merits