Rotation, the equivalence principle, and the Gravity Probe B experiment

Area of Science:

• Physics
• General Relativity
• Experimental Physics

Background:

• The weak equivalence principle (WEP) is a cornerstone of general relativity.
• Testing WEP under rotational conditions is crucial for understanding gravity.

Purpose of the Study:

• To test WEP II, which incorporates rotation into universal free-fall.
• To constrain parameters related to rotational effects on free-fall using Gravity Probe B data.

Main Methods:

• Utilized data from the ultraprecise Gravity Probe B experiment.
• Analyzed measurements from four quartz gyroscopes.
• Applied results to test WEP II for rotating bodies.

Main Results:

• Constrained the free-fall Eötvös parameter (η) for a rotating body to ≤10⁻¹¹, a four-order improvement.
• Established stringent limits on the anomalous torque parameter (λ) and frequency-dependence parameter (κ).

Conclusions:

• The Gravity Probe B experiment provides the most precise test of WEP II to date.
• The results strongly support the predictions of general relativity concerning rotational effects on free-fall.