Torsion Balance and Remeasurement of the Eötvös Experiment
Between 1906 and 1908 Roland (Loránd) Eötvös and his colleagues Dezső Pekár and Jenő Fekete made measurements with revolutionary precision (the EPF measurement) for validating the equivalence of gravitational and inertial mass. Almost 80 years later, in 1986, Ephraim Fischbach and his colleagues reanalyzed the results of the EPF measurement and discovered a correlation between the small violations and some atomic parameter. Finally they were unable to reproduce this correlation experimentally, but there is still no valid explanation of these differences in the EPF results. Our analysis of the EPF experiment pointed to a possible bias that justifies repeating the tests under better conditions and using modern new technology. Planning and preliminary measurements started at July of 2017. Participants are from Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Department of Geodesy and Surveying of Budapest University of Technology and Economics (BME), Society for the Unity of Science and Technology (SUST), and the Department of Control Engineering and Information Technology of BME in cooperation with other organizations, departments and experts. After more than one year of thoughtful preparation, in December 2018 preliminary tests have been started in a controlled and undisturbed environment of the Jánossy Underground Physics Laboratory at KFKI, 30 meters below ground level. This paper gives a brief overview of the basic physics, history, preparations and present status of the new experiments. Another good reason for repeating the EPF measurements is that 2019 – as the 100th anniversary of Eötvös’s death – is referred as “Eötvös year”.