The STEP mission, aimed at testing the Equivalence Principle with unprecedented precision from 1 part in 10^13 to 1 part in 10^18, has been canceled. This landmark experiment in Fundamental Physics was expected to significantly impact gravitation theory, cosmology, and the evolution of the Universe. The cancellation is speculated to be due to funding issues, with no current plans for a similar mission in the near future. A null result from STEP would impose severe constraints on new theories, while a positive result could indicate the discovery of a new force of Nature.
PREREQUISITESPhysicists, researchers in Fundamental Physics, and anyone interested in the implications of experimental results on theories of gravitation and cosmology.
STEP will advance the testing of the Equivalence Principle from several parts in 1013 to 1 part in 1018. Whether it confirms Equivalence five to six orders of magnitude more precisely than known today or discovers a violation, it will be a landmark experiment in Fundamental Physics, with consequences extending from gravitation theory to cosmology to theories of the evolution of the Universe. It will probe a large and otherwise inaccessible domain in the parameter space of new interactions. A null result would remain for many years a severe constraint on new theories. A positive result would constitute the discovery of a new force of Nature.