Nina investigates how we know the Earth is round, with the help of Luke - her sight neuron.

Originally released by BBC, 2013. Streaming video file encoded with permission for digital streaming by Infobase on November 17, 2016.

Meet the Neurons (0:55); --How Do We Know the Earth is Round? (2:17); -- Senses Experiment (3:16); -- Launching a Camera Equipped Balloon (2:47); -- High Altitude Photos of Earth (2:50); -- Summary: How Do We Know the Earth is Round? (0:33); -- Credits: Earth Is Round—Nina & the Neurons: Earth Explorers (1:32); .