Pedagogy: The Bubble Analogy and the Difference Between Gravitational Forces and Rocket Thrust in Spatial Flow Theories of Gravity
Thomas D. Martin
We present a physical analogy which can be used to understand the issues involved in the Principle of Equivalence in so-called spatial flow theories of gravity, and we discuss the essential kinematic properties of the flow which distinguish its gravitational, non-inertial, and inertial modes. We also point out that the acceleration experienced by a body moving in the flow does not always coincide with the co-moving derivative of the flow itself.
