Unexplained

Short, surprising cards on unexplained. Each one is labelled Established, Debated or Speculative, so you always know how solid the evidence is.

• Did a comet end the last Ice Age, then bring it back?

  Debated. Around 12,900 years ago, the world was warming fast. Then it suddenly plunged back into cold for about 1,200 years. Some researchers think…

• Is the Great Sphinx much older than we think?

  Debated. Geologist Robert Schoch argued in the 1990s that deep weathering around the Sphinx was caused by heavy rainfall, which would point to a…

• Where did the story of Atlantis come from?

  Speculative. Atlantis first appears in two dialogues by the Greek philosopher Plato, written around 360 BCE. He describes a powerful island that sank in…

• A former intelligence officer told Congress the US has "non-human" remains.

  Debated. On 26 July 2023, David Grusch testified under oath that the US runs a secret programme to retrieve crashed craft of non-human origin. He…

• Navy pilots chased something they still cannot explain.

  Established. In 2004, pilots from the USS Nimitz encountered a white, oblong object off California that seemed to move in ways no known aircraft could.…

• In 1977, a radio telescope caught a signal so strong someone wrote "Wow!".

  Established. On 15 August 1977, the Big Ear telescope in Ohio picked up a 72-second burst of radio waves from the direction of Sagittarius. Astronomer…

• A stone 'road' appeared off the Bahamas just when a psychic said Atlantis would rise.

  Debated. In 1938, Edgar Cayce predicted part of Atlantis would be found near Bimini in 1968 or 1969. In 1968, divers found a long line of flat,…

• Is there a sunken pyramid off Japan?

  Debated. In 1986, a diver off Yonaguni Island found huge underwater rock terraces with flat surfaces and sharp right angles. Marine geologist…

• Some people hear a low hum that no microphone picks up.

  Debated. In places like Taos in New Mexico and Bristol in England, a small share of people report a constant low droning sound, like a distant…

• Nine hikers fled their tent into a frozen night. Why?

  Debated. In 1959, nine experienced hikers died in Russia's Ural Mountains. Their tent was cut open from inside, and some were found barefoot in the…

• A clay disc from Crete holds a message no one can read.

  Debated. The Phaistos Disc, found in 1908, is covered in a spiral of 241 stamped symbols on both sides. It is thought to date from around 1700 BCE.…

• In 1872, a ship was found sailing with no one on board.

  Debated. The Mary Celeste was found drifting in the Atlantic, in fair condition, with food, water and cargo aboard. The captain, his wife, their…

• Glowing balls of light sometimes float through storms, and even into houses.

  Established. For centuries, people have reported ball lightning: glowing orbs that hover, drift and vanish, sometimes indoors. Scientists long doubted…

• In 1908, something flattened 80 million trees in Siberia but left no crater.

  Established. A huge explosion over the Tunguska River in Russia flattened forest across about 2,000 square kilometres. People 60 km away were knocked…