EntityQ966914· pop 12· linked from 19 articlesgravity trainSign in to savetype of trainConnectionsEarthConceptIsaac NewtonPersonplanetEntitytransportEntitygravityEntityLewis CarrollEntityaccelerationEntityCeresEntitymass densityEntitysphereEntitydiameterEntitydigital object identifierEntityRobert HookeEntityTimeEntitytunnelEntityfrictionEntitypendulumEntityspringEntityinclined planeEntitymantleEntityCategoriesDifferential equationsFictional technologyGravityHigh-speed railHypothetical technologyMechanicsTravel to the Earth's center