1. The problem statement, all variables and given/known data How far would be a planet from the earth, when its period would be 2 years? T = 2 years/730 days a = 150*106km 2. Relevant equations a3/T2 = C (C is the Kepler-Constant) 3. The attempt at a solution I tried inserting T in days and years, but I always get a wrong solution, since C (The distance from earth) does need to increse if it needs longer for its period. Any idea why?