Long-Delayed Echoes

Long-Delayed Echoes are a peculiar radio phenomenon where a transmitted signal returns after an unexpected delay of several seconds to minutes. First reported in the 1920s, these echoes defy conventional radio wave propagation physics. While theories suggest natural explanations like plasma interactions in the magnetosphere, their unusual timing and selective nature have also sparked speculative, though unproven, ideas about intentional retransmission by an unknown intelligence.