Fourth Test of General Relativity: New Radar Result

Irwin I. Shapiro; Michael E. Ash; Richard P. Ingalls; William B. Smith; Donald B. Campbell; Rolf B. Dyce; Raymond F. Jurgens; Gordon H. Pettengill

doi:10.1103/PhysRevLett.26.1132

Fourth Test of General Relativity: New Radar Result

Irwin I. Shapiro, Michael E. Ash, Richard P. Ingalls, William B. Smith, Donald B. Campbell, Rolf B. Dyce, Raymond F. Jurgens, and Gordon H. Pettengill

Phys. Rev. Lett. 26, 1132 – Published 3 May 1971

Abstract

New radar observations yield a more stringent test of the predicted relativistic increase in echo times of radio signals sent from Earth and reflected from Mercury and Venus. These "extra" delays may be characterized by a parameter $λ$ which is unity according to general relativity and 0.93 according to recent predictions based on a scalar-tensor theory of gravitation. We find that $λ = 1.02$ . The formal standard error is 0.02, but because of the possible presence of systematic errors we consider 0.05 to be a more reliable estimate of the uncertainty in the result.

Received 15 March 1971

DOI:https://doi.org/10.1103/PhysRevLett.26.1132

Authors & Affiliations

Irwin I. Shapiro^*, Michael E. Ash^†, Richard P. Ingalls^‡, and William B. Smith^†

Massachusetts Institute of Technology, Cambridge, Massachusetts 02319

Donald B. Campbell, Rolf B. Dyce, Raymond F. Jurgens^§, and Gordon H. Pettengill^∥

Arecibo Observatory, Arecibo, Puerto Rico

^*Department of Earth and Planetary Sciences and Department of Physics.
^†Lincoln Laboratory, Lexington, Mass. 02173; supported in part by the U. S. Department of the Air Force.
^‡Haystack Observatory.
^§Now at University of Ohio, Athens, Ohio 45701.
^∥Now at the Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Mass. 02139.