Showing that this quantity is constant outside of general relativity requires t−φ (“t-phi”) orthogonality. Bardeen, Carter, and Hawking showed that in GR, this quantity of a black hole is constant if the stress-energy tensor satisfies the dominant energy condition. The third law of thermodynamics for black holes says this quantity cannot reach zero. This quantity is analogous to thermodynamic (*) temperature for black holes, (-5[1])since in Planck units, Hawking temperature equals this quantity over 2 pi. This quantity classically equals "big G times mass over radius-squared" for both stationary black holes and general celestial objects. This quantity is the magnitude of a vector that is perpendicular everywhere to the geoid (“gee-oid”). For 10 points, name this quantity equal to about 9.8 meters (-5[1])per second-squared for the Earth. ■END■