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James M. Bardeen developed methods for interpreting motion near rotating black holes. His 1972 paper with William H. Press and Saul Teukolsky introduced a practical local-frame treatment for particle orbits and radiation in the Kerr metric.

Locally nonrotating observers provide an orthonormal frame tied to the rotating geometry. Expressing measurable quantities in that frame clarifies which effects reflect local motion and which involve frame dragging.^[ref]

Saul Teukolsky studied particle orbits and radiation near rotating black holes with James M. Bardeen and William H. Press. Their 1972 work used locally nonrotating orthonormal frames to express physical measurements in the Kerr metric.

This separates locally measured particle speeds from coordinate behavior affected by frame dragging. The paper applied the method to energy extraction and radiation, testing whether a formally allowed process could operate on physically reasonable orbits.^[ref]

William H. Press coauthored a quantitative treatment of physical processes around rotating black holes. With James M. Bardeen and Saul Teukolsky, he organized measurements using locally nonrotating frames in the Kerr metric.

Their applications distinguished a permitted energy-extraction process from an efficient astrophysical mechanism. Studying the required local particle velocities and orbits exposed restrictions that an energy-conservation argument alone would miss.^[ref]