On apple mass and other matters

© Spektr-R spacecraft image: courtesy of Lavochkin Scientific and Production Association

Are 150 grams measured by a shopping scale in a grocery store the same 150 grams that caused the well-known �apple incident� with Isaac Newton, which led him to formulate the law of universal gravitation? The former �150 grams� is a so called �inertial mass�, the latter - a �gravitational mass�. If you are not sure about the right answer about those 150 grams, ask Giovanni Granato. Until Wednesday, 20 February 2019, he was a MSc student of the Aerospace Faculty of the Delft University of Technology and a JIVE trainee. Now he is Ingenieur Giovanni Granato. He knows the answer which would probably please Albert Einstein. And the answerer is affirmative, with the precision of �

If you are anxious to know what is the precision - read and try to understand the MSc thesis successfully defended by Giovanni on 20 February 2019. He conducted the study of the Gravitational Redshift Experiment with the Space VLBI mission RadioAstron under a co-supervision by Dominic Dirkx of TU Delft (and a former JIVE staff member) and the undersigned. The aim of the project was to verify one of the pillars of the modern fundamental physics, the Einstein Equivalence Principle (EEP), which does equate the inertial mass and gravitational mass. But physicists do not take this equivalence for granted and try to test it experimentally.

The space-borne radio telescope of the RadioAstron mission was equipped with a Hydrogen maser oscillator as a part of the mission VLBI instrumentation. It was the first active H-maser oscillator flown in space aboard a science mission. Its prime task was to support VLBI observations with RadioAstron in the same way as done at any VLBI radio telescope on the ground. But when the on-board instrumentation was not observing in the VLBI mode, an international team of investigators conducted an ad hoc Gravitational Redshift Experiment measuring minuscule differences in the oscillations rate of the on-board and ground-based H-masers. Giovanni was a member of this team and grabbed the opportunity to impress the MSc committee at the TU Delft with the results of his study. This brave move was very successful. Well done Giovanni! Good luck in your future professional steps!