The figure, drawn by Isaac Newton, shows how projectile motion on curved earth produces orbital motion. All projectiles are launched horizontally, with greater and greater initial velocities. As a result they land further and further from the launch point. Eventually the landing point reaches the launch point, which is to say, the projectile is back where it started with the same velocity: it will repeat its motion indefinitely.
From "Physics, Classical and Modern 2nd ed.", by Keller, Gettys, and Skove, McGraw-Hill.