One thing science sometimes isn’t is straightforward. In the first half of the last century, Einstein redefined how we see our universe with his introduction of relativity. His work, which many non-scientists still struggle to accept, describes interactions between mass-energy – interactions like the orbit of the Moon and the bending of light around our Sun – as being a reflection of how our universe’s structure is shaped by gravity. According to his theory, any two masses in a gravitational field will fall at the same rate. Astronaut David Scott demonstrated this with a hammer and feather on the Moon in 1971, and today, two masses – platinum and titanium alloy test masses – repeated this experiment in orbit with remarkable precision by the MICROSCOPE mission.

The reason for this experiment was to see if the tiny quantum fluctuations that permeate our reality could be seen to affect gravitational interactions. The two masses were contained within a larger sphere set orbiting our Earth, and electrostatic forces were used to see if the two masses fell around the Earth in their orbit with any differences. These measurements were accurate to one part in 10^15 and, according to a new paper in Physical Review Letters, they saw nothing.

This means that while we can detect the quantum vibrations in mirrors using lasers, we don’t see anything similar with gravity. This once again seems to indicate that Einstein’s geometry-based description of gravity resists being combined with the particle-based descriptions of all the other forces using quantum mechanics.

I, for one, like my spacetime curvy and welcome this lack of measurable quantum variations in these orbiting masses.

More Information

ONERA press release (French)

MICROSCOPE mission presents most precise test of general relativity’s weak equivalence principle (EurekAlert)

“MICROSCOPE Mission: Final Results of the Test of the Equivalence Principle,” Pierre Touboul et al., 2022 September 14, Physical Review Letters