vf = v0 + at where vf = final velocity and v0 = initial velocity and a = acceleration and t = time in seconds We solve it for t at = vf - v0 t =The speed of light is 299792458 m/s, 90% of that is 269813212.2 m/s so that will be vf. We will assume starting from rest so we will use v0 = 0 1 G is the acceleration = 9.81 m/sē, we substitute in t = t = t = 27503895.2 seconds = 458398.3 hours = 19099.9 days = 52.3 years. Edwin