 How do we decide? This will depend on the particular measurement (see e.g., Kamionkowski &amp; Loeb 1997; Marra et al. 2013), but in general because of the uniqueness of the universe, we don’t know if these potential anomalies are real, pointing to serious problems with the models, or not real—just statistical flukes in the way the family of models differs from the one instance that we have at hand, the unique universe that actually exists. In all the physical sciences, this is a unique problem of  cosmology.[29] 