ScienceSpaceWhat causes mysterious long delayed radio echoes in Earth's atmosphere?
The mysterious long delayed radio echoes first heard in 1927 still have no confirmed explanation, with theories ranging from atmospheric phenomena to extraterrestrial technology.
Baffling long radio echo delays have prompted a range of potential explanations, most of which focus on a variety of unexplained natural phenomena occurring in Earth's atmosphere.
Norwegian engineer Jørgen Hals first recorded strange radio echoes arriving about three seconds after transmission back in 1927, and scientists still cannot explain them.
Long delayed echoes are defined as radio signals returning more than 2.7 seconds after transmission, and their timing and nature vary unpredictably, making them very hard to study.
Proposed explanations range from unexplained atmospheric phenomena to, in a few more speculative cases, possible evidence of extraterrestrial technology.
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