A space elevator is a proposed megastructure designed to transport material from a celestial body's surface into space. The term most often refers to a structure that reaches from the surface of the Earth to geosynchronous orbit (GSO) and a counter-mass beyond. The concept of a structure reaching to geosynchronous orbit was first conceived by Konstantin Tsiolkovsky., who proposed a compression structure, or "Tsiolkovsky tower." Most recent discussions focus on tensile structures (tethers) reaching from geosynchronous orbit to the ground. Space elevators have also sometimes been referred to as beanstalks, space bridges, space lifts, space ladders, skyhooks, orbital towers, or orbital elevators.