5.
There’s a mysterious radio station in Russia that broadcasts buzzing, beeping, and humming sounds, occasionally interrupted by voice messages that list callsigns and codes. No one knows the purpose of the broadcast, outside of perhaps the Russian military.
People have been listening in to the broadcast since it started in the 1990s, attempting to figure out why it exists in the first place. Due to some occasional irregularities (including human conversations heard in the background), it’s believed that the broadcast is not automated, and the sounds are instead being made in front of a live microphone. Theories include the possibility that it’s a “Dead Hand” signal, designed to launch an automatic retaliation in the event that Russia is annihilated in a nuclear attack. Or, it could be some sort of encoded communication within the Russian military, or among Russian spies. Nobody knows.
Source: https://www.buzzfeed.com/andyneuenschwander/eerie-facts-that-keep-me-up-at-night