According to Newton when the distance between two bodies is doubled, gravity is decreased 1/4 of its force. However in M-Theory this works within 3D only while in 4D the gravity is decreased by 1/8 when the distance between two bodies is doubled. Also when you go in 5D gravity will be 1/16 and so on.. What is the meaning of this? Stephen hawking says that elliptical orbits can only exist in 3D, while circular orbits are possible in higher dimensions but they will no longer be stable. if we assumed a planetary object orbiting a star in higher dimensions the orbit won't be stable ( orbital perturbations won't be allowed ). when other planets or any object act with a force on a planet, the planetary orbit won't be stable at all causing the planet to move in a spiral towards the star and fall inside it or to move in a spiral away from that star... And this is how gravity is weird in higher dimensions..