1. The problem statement, all variables and given/known data What is the Kinetic Energy of the Earth Orbiting Around the Sun in Joules? 2. Relevant equations E rotation = (1/2)* I * w^2 where I = moment of Inertia where w = angular velocity 3. The attempt at a solution Well, this is my predicament: I don't know whether my professor wants me to use the above equation or not, but I don't know any other way to solve it. My answer is comes out to somewhere around 10^29, while his is around 10^33. So obviously something must be wrong.... My solution: Earth's period = 23.93 hours Therefore, its angular velocity is 7.29×10^ -5 rad·s-1. Assuming that the Earth is perfectly spherical and uniform in mass density, it has a moment of inertia, I = 9.72×10^37 kg·m2. Therefore, it has a rotational kinetic energy of 2.58×10^29 J. Is this right? Or am I missing something completely? Thanks a lot.