General Relativity and Gravitation

, Volume 36, Issue 10, pp 2331–2339 | Cite as

Equivalence Principle Measurements

  • T. J. Sumner


Over the centuries there have been many experimental tests of the “universality of free-fall.” To date, these measurements have established the equivalence between inertial and gravitational mass to high precision, justifying its use as a foundation stone of general relativity by Einstein. There is a surprising richness in the variety of techniques and choice of test bodies which have been used so far, and a brief review is presented. However, future space experiments promise much better precision in this measurement and STEP is presented in some detail as one of a number of such missions. Using pairs of concentric free-falling proof-masses, STEP will be able to test the Equivalence Principle (EP) to a sensitivity at least five orders of magnitude better than currently achievable on ground. The EP is a founding principle of general relativity and STEP is the most sensitive experiment of this type planned so far, aiming at 1 part in 1018.

STEP universality of free fall equivalence principle 


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Copyright information

© Springer Science+Business Media, Inc. 2004

Authors and Affiliations

  • T. J. Sumner
    • 1
  1. 1.Department of PhysicsImperial College LondonLondonUnited Kingdom

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