ILL: Analysing gravity at the atomic scale

EIROforum Scientific Highlight, ILL: Analysing gravity at the atomic scale

The instrument PF2, a powerful source of ultra-cold and very cold neutrons
Image courtesy of ILL / Artechnique

September 2011 - How does gravity work at the (sub)atomic scale? Do Newton’s laws apply, as they do for stars and planets, or do different laws apply at this scale? This important question is being addressed with gravity resonance spectroscopy, a technique developed by scientists from the Institut Laue-Langevin (ILL) and from the Vienna University of Technology, Austria.

The new technique involves bouncing ultra-cold neutrons on a mirror vibrating at a precisely defined frequency. When this frequency corresponds to the energy difference between two quantum states, the neutrons are excited to the next higher energy state.

The technique provides measurements of unrivalled precision, which can be used to test whether gravity accelerates all objects equally, regardless of their mass, even at the atomic level. This is what would be expected from the equivalence principle, proposed in the 16th century.

Some physicists also believe that the experiments will reveal a slight divergence from quantum energies calculated using Newton’s laws of gravity. This could provide evidence of dark matter particles known as axions, or of the extra dimensions suggested by string theory.

To learn more, see the ILL press release