New tests of Einstein's equivalence principle and Newton's inverse-square law

This paper describes recent experimental work by the University of Washingt on Eot-Wash group on two different topics: a test of the strong equivalence principle and a search for sub-millimetre scale deviations of the Newtonia n 1/r(2) law. Our strong equivalence principle test was motivated by the re surgence of interest in 'gravitational' scalar fields, which typically lead to violation of the equivalence principle for gravitational self-energy. O ur sub-millimetre experiment was motivated by predictions of fundamentally new effects from 'large' extra dimensions and from the dilaton and moduli s calar particles of string theory.