"Lorentz symmetry might be broken but there doesn't really exist a glimpse of evidence or motivation why it should be broken. Such a breaking might be studied as a possibility, to some extent, but it would cause many problems, it would most likely return us philosophically before 1905, and the people who say that such a breaking is needed in quantum gravity are clearly wrong because string theory satisfies all the required properties of quantum gravity but it also respects the Lorentz invariance in flat space."