Imagine you are on a point on the inner circle in space and the inner circle is spinning. You would experience the constant change of direction and being thrown away from the center. Now imagine you're on the same spot on the inner circle, except this time it's stationary and it's the outer circle that's spinning. Relative to the outer circle, you and the inner circle are spinning exactly as before. Except this time, you don't feel like you're being thrown away from the center, or any change of direction. Relative to what? the imaginary frame of reference?