During October 1971, four cesium beam atomic clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicts that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40 +/- 23 nanoseconds during the eastward trip, and should have gained 275 +/- 21 nanoseconds during the westward trip. The observed time differences are presented in the report that follows this one.

Four cesium beam clocks flown around the world on commercial jet flights during October 1971, once eastward and once westward, recorded directionally dependent time differences which are in good agreement with predictions of conventional relativity theory. Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59 +/- 10 nanoseconds during the eastward trip and gained 273 +/- 7 nanoseconds during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks.

Relative to a clock at rest on the Earth's surface, the time recorded by an ideal clock after a circumnavigation of the Earth depends not only on the speed and altitude but also on the direction of the circumnavigation and on the rotational speed of the Earth. Such a clock may run either fast or slow, depending on the direction and ground speed for the circumnavigation. This directional dependence should be perceptible with commercial jet speeds and cesium beam clocks.

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Measured differential cross sections are reported for 30-MeV 3 He ions elastically scattered from 27 A1, 51 V, 69 Co, 60 Ni, 89 Y, 114 Cd, 115 In, and 116 Sn for angles between 6° and 165° and for 35-MeV 8 He ions elastically scattered from 69 Co, 60 Ni, 116 In, and 116 Sn for angles between 6° and 140°. The data are compared with predictions of the nuclear optical model, and potential parameters that produce optimum fits with a leastsquares computer routine are reported. Good fits at back angles for 27 A1, 51 V, 59 Co, and 60 Ni are obtained only with the inclusion of a spin-orbit interaction with a magnitude between 2 and 5 MeV for most cases. The back-angle data for these nuclei also tend to suppress discrete ambiguities in the potential well depths. A continuous ambiguity between the radius and the diffuseness parameters is found to be related to a constancy of the root-mean-square radius. Effects of experimental uncertainties on the potential parameters are also presented.