Starting with the logical roots of arithmetic with negative numbers, Marcus du Sautoy explains how mathematicians created imaginary numbers by 'imagining' the square root of -1. Though imaginary in nature, he then explores how this abstract mathematical idea has become vital to air traffic control systems. Teacher notes: Use as an enrichment and extension clip during a series of lessons on negative numbers or powers and roots

Originally released by BBC Worldwide Learning, 2020. Streaming video file encoded with permission for digital streaming by Infobase on October 27, 2020.

The Unbelievable Truth (Imaginary numbers at use in the real world) (4:33); .