Monday, March 26, 2018

Newton's Gravitational Law Still Valid At Sub-Nanometer Scale

A new experiment using neutron scattering off noble gasses has shown no deviation from Newton's gravitational law at 0.1 nm scale.

The team fired pulses of neutrons at a chamber filled with either helium or xenon gas and monitored both the travel time of the neutrons through the gas and the neutrons’ scattering angles. From these measurements, they reconstructed the scattering process with the aid of simulations. They found that the scattering-angle distribution fit the predictions—based only on known laws of physics—for neutrons bouncing off gas nuclei. This result indicates that, within the sensitivity of the experiment, no unexplained force—be it modified gravity or another type of interaction—acts on length scales below 0.1 nm.

This one may not be as transparent, since it required quite a bit of reconstruction to simulate the interaction. So while the length scale being probed has improved considerably, I'm not so sure on how convincing this result is.

Still, where are those curled-up extra dimensions anyway?


1 comment:

Douglas Natelson said...

Notice that they only rule out forces 10^24 times larger than gravity. In other words, the gravitational interaction between neutrons and those nuclei is, as expected, really really weak. Still a cool experiment, but they did not actually measure that gravitational interaction.