Synopsis: Testing Relativity with Planetary Motion  

Observations of the orbital motion of planets around the Sun allow researchers to place stringent limits on Lorentz symmetry violations.

Lorentz invariance is a central tenet of general relativity and the standard model of particle physics. It states that any two observers moving through space at a constant velocity share the same laws of physics, no matter their orientation and velocity. Any hint of breakdown of this spacetime symmetry could guide researchers in the search for a theory that unifies relativity and the standard model. Aurelien Hees from Rhodes University, South Africa, and colleagues report a test of Lorentz symmetry based on existing observations of the orbits of planets around the Sun. Their study indicates no breakdown of Lorentz invariance but places stringent constraints on it.

Lorentz symmetry can be tested using the so-called standard model extension (SME). This framework describes Lorentz symmetry for all known particles and forces, including gravity, in terms of coefficients that vanish when the symmetry holds exactly. Hees and colleagues determined SME coefficients using the observed shifts of two planetary orbital elements: the longitude of the ascending node (the point where a planet crosses the plane of Earth’s orbit from south to north), and the argument of the perihelion (the angle between the ascending node and the point of closest approach to the Sun). These shifts depend on other observables—such as a planet’s mean motion, orbital eccentricity and inclination—as well as on some of the SME coefficients. Therefore, they can be used to derive the values of the latter. The team found that these SME coefficients are zero to an accuracy on the order of parts per billion or less, improving current limits set by Solar System tests by ten- to a thousand-fold.

This research is published in Physical Review D

–Ana Lopes


More Features »


More Announcements »

Subject Areas

Particles and FieldsAstrophysicsGravitation

Previous Synopsis

Fluid Dynamics

A Diode for Fluids

Read More »

Next Synopsis


Bright Twins

Read More »

Related Articles

Viewpoint: Dark Matter Still at Large

Viewpoint: Dark Matter Still at Large

No dark matter particles have been observed by two of the world’s most sensitive direct-detection experiments, casting doubt on a favored dark matter model. Read More »

Viewpoint: New Clues as to Why Boyajian’s Star is Dimming
Statistical Physics

Viewpoint: New Clues as to Why Boyajian’s Star is Dimming

A statistical analysis links a star’s mysterious brightness fluctuations to internal nonequilibrium phenomena, rather than structures orbiting around the star. Read More »

Viewpoint: Searching for Baby Planets in a Star’s Dusty Rings

Viewpoint: Searching for Baby Planets in a Star’s Dusty Rings

Images of gaps in the dust and gas around a young star provide the best evidence to date that these gaps host newly formed planets. Read More »

More Articles