One way is to probe them indirectly. For example, string cosmology makes testable predictions (verifiable by observation, e.g. of the CMB). Conceivably, evidenc

One way is to probe them indirectly. For example, string cosmology makes testable predictions (verifiable by observation, e.g. of the CMB). Conceivably, evidence could be found of something that happened in the early universe that is most easily explained within the string theory.