Magnetic energy
From Tardis Wiki, the free Doctor Who reference
During a conflict between Kallix Grover and the Sine Wave Shrine of Shillitar in 436,000, a wave of magnetic energy hit Earth by mistake. The vast grid of nanotechnology was wiped out and Earth was cut off from space. "The Great Retrenchment", a 10,000 year Dark Age began and humans turned to biology and chemistry. (PROSE: Only Human)
