Hello all. I'm trying to determine the mass of an object required to make it so that a traveler on a massive planet experiences 1 day but on earth, or some infinitely distance away from the planet, 1000 years passes by. I'm using the following equation: t0 = tf*root(1-(2GM/rc^2)) Found here: https://en.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere I'm trying to solve for M. I end up with the following equation: M = rc^2 * (1 - (t0/tf)^2)/2G I arbitrarily picked r = 1 * 10^6 meters. When I run through this equation I get a negative mass. What am I doing wrong? P.S. This is not a homework assignment, I'm just a curious guy trying this equation out.