International Journal of Science, Engineering and TechnologyAuthors: Mario Nascimento, Joao Silva, Mariana Alves
Abstract: We determine the local gravitational acceleration and potential with three indepen- dent ultra-high-vacuum (UHV) instruments: (i) a dual-species 87Rb / 39K Mach–Zehnder atom interferometer, (ii) laser-tracked free-fall of centimetre spheres whose bulk den- sities differ by a factor eight, and (iii) a vertically separated pair of 87Sr optical-lattice clocks. All experiments operate below 10−5 Pa, where hydrostatic forces are < 10−11 of the test weight. The three sensors yield g = 9.803 07 ± 0.000 07 m s−2 (atom interferom- eter, Rb), g = 9.803 02 ± 0.000 29 m s (free fall), and g = 9.804 ± 0.0017 m s (optical clocks), in mutual agreement at the 3 × 10 level. A pressure-variation study up to 10−1 Pa shows no discernible change in g (∂g/∂p = −0.8 ± 1.7 × 10−5 m s−2 Pa−1). The fractional differential acceleration between the two atomic species is η < 7.6×10 (95% C.L.), confirming the composition independence of free fall. Because the quantum phase (interferometer) and fractional frequency shift (clocks) cannot be generated by hydrostatic pressure, and the classical drop occurs where such pressure is negligible, the data establish gravity—not density sorting or buoyancy—as the unique driver of weight and free fall.
