The interpretations by experimenters of experiments on 'time dilation': 1940-1970 circa

TL;DR

This paper reviews historical experiments on time dilation from 1938 to 1970, highlighting how interpretations often relied on extraneous assumptions, and concludes that only particle-based experiments in inertial flight provide unambiguous tests.

Contribution

It critically analyzes the assumptions behind historical time dilation experiments and clarifies which experiments genuinely test the theory without extraneous hypotheses.

Findings

Experiments with elementary particles in inertial flight are the only unambiguous tests.

Many historical experiments relied on extraneous assumptions like clocks measuring proper time.

Interpretations often included hypotheses not necessary for the formal theories.

Abstract

Experimental tests on `time dilation' began in 1938 with Ives and Stilwell's work of the transverse Doppler effect due to atoms in inertial flight. Rossi and Hall (1941) inaugurated the era of fast moving elementary particles that dominated the scene until the discovery of the Mossbauer effect (1957). This discovery suggested the use of photons emitted without recoil in crystalline solids for testing both time dilation and gravitational red shift. Finally, around 1970, Hafele and Keating dealt again with time dilation by sending macroscopic atomic clocks around the Earth. The interpretations of these experiments by experimenters have been characterized by the use of additional hypotheses not necessary for the formal development of the theories under test (the idea that all clocks measure proper time) or hypotheses completely extraneous to the theories themselves (the idea that atoms are clocks). If these assumptions are dropped, it turns out that the only experiments concerning time dilation are those performed with elementary particles in inertial flight. The historical and epistemological implications are discussed.