Editing Black Knight Satellite — Long-Delayed Echoes (1927–1934) (section)

=== Jorgen Hals and the 1927 Discovery ===
Norwegian amateur radio operator '''Jorgen Hals''' of Bygdo, Oslo, is credited with the first systematic documentation of the LDE phenomenon. In 1927, while experimenting with his radio equipment, Hals noticed that signals were echoing back to him approximately '''15 seconds''' after transmission — a delay far longer than any known propagation mechanism could produce at the time.

He reported his observations to prominent Dutch physicist '''Balthasar van der Pol''' at Philips Research Laboratories. Van der Pol and his colleague Karl Posthumus were already conducting radio propagation experiments in collaboration with Carl Stormer in Norway; they were able to reproduce and document the LDE phenomenon independently.

Over the period 1928–1934, multiple radio researchers across Europe documented LDE occurrences, with delays ranging from 3 to 15 seconds reported across different experiments.