Tesla Observes Stationary Waves at Colorado Springs

On the night of 3 to 4 July 1899, during a thunderstorm with 10,000 to 12,000 lightning discharges in two hours, Nikola Tesla observed periodic impulses on his rotating-coherer receiver at his Colorado Springs laboratory. The instrument continued to register impulses at near half-hour intervals even after the storm receded beyond 200 miles. Tesla concluded the observation proved 'the existence of stationary waves' in the earth — a conclusion he later reframed publicly in his June 1900 Century essay and his February 1901 Collier's article as the possible reception of interplanetary signals.