Starting from a grand plan of a domestic sci-fi blockbuster“The Wandering Earth”，the minimum mechanical work needed to take the earth out of the solar system is deduced and calculated by using the law of conservation of momentum，theorem of kinetic energy，and concept of escape velocity and effective recoil jet velocity. The result is 2.72×1032 J，and the possibility of separating the earth from the solar system is discussed from the perspective of energy.