Flat galaxy rotation curves are unexpected observations. Differences between expectations and observations allow us to learn. Most cosmologists today attribute the difference between observed flat and calculated declining Newtonian velocity curves to dark matter despite decades of failed efforts to identify it. This paper examines data for five galaxies. Physics for flat galaxy velocity curves is proposed that preserves Newtonian gravitation and explains the flat velocity profiles. The proposal shows that there are two components to the redshift (gamma) measured to determine velocity. One component is the normal kinetic energy gained as a particle falls toward a galaxy. The kinetic energy component obeys Newtonian velocity that decreases with distance from the center of the galaxy. But potential energy increases with distance from the center and the two energy components add to a constant value. We measure this constant energy associated with constant velocity across the galaxy toward the edge. The kinetic energy component is a vector but the potential energy component is a scalar. Both components change gamma and allow us to measure the velocity from time0; i.e. t2/t1*t1/t0=t2/t0. Our observations are based on gamma that does not distinguish the two gammas involved. The calculation procedure is straightforward and matches data for five galaxy data sets examined. Dark matter is not required in this approach.