Where Does Earth's Gravity End? MMX and the Sphere of Influence

概要

Does a spacecraft ever completely leave Earth's gravity? We explain the Laplace sphere of influence, calculate Earth's reference radius, and estimate when MMX crossed it using the saved predicted trajectory. The sphere of influence is a guide for joining simplified Earth-centred and Sun-centred orbit models. It is not a physical wall or a boundary where Earth and the Sun pull equally hard. Earth's gravity continues beyond it. r ≈ a × (m_Earth / M_Sun)^(2/5) With a = 149,597,870.7 km and the ma...