  An important open question in fundamental physics concerns the nature of
spacetime at distance scales associated with the Planck length. The widespread
belief that probing such distances necessitates Planck-energy particles has
impeded phenomenological and experimental research in this context. However, it
has been realized that various theoretical approaches to underlying physics can
accommodate Planck-scale violations of spacetime symmetries. This talk surveys
the motivations for spacetime-symmetry research, the SME test framework, and
experimental efforts in this field.
