Natural Phenomena That Still Surprise

Still in the Open Drawer

The Wow! Signal

On 15 August 1977, the Big Ear radio telescope at Ohio State University recorded a strong, narrowband signal near the hydrogen line at about 1420 MHz. It rose and fell over roughly 72 seconds, exactly as a fixed point in the sky would as Earth rotated the telescope's beam past it. Days later, volunteer astronomer Jerry Ehman reviewed the printout, circled the sequence "6EQUJ5" and wrote "Wow!" in the margin.

Repeated searches of the same patch of sky, in Sagittarius, have heard nothing. Proposed explanations have ranged from terrestrial interference to a hydrogen cloud suddenly brightened by a passing source. None has been confirmed.

Known

The recording, its frequency and its duration.

Guessed

Interference, an astrophysical flare, or an artificial source.

Open

The source, and why it never repeated.

Ball Lightning

Witnesses have described glowing spheres drifting during thunderstorms for centuries, occasionally entering buildings and vanishing with a bang. Scientists long had only testimony. In 2012, researchers in China studying ordinary lightning on the Qinghai Plateau accidentally captured video and a spectrum of a ball lightning event; it contained elements from the local soil, supporting one theory involving vaporised silicon. One recording, however, cannot settle the many competing models.

Known

It exists; one spectrum shows soil elements.

Guessed

Vaporised soil, microwave cavities, plasma effects.

Open

A mechanism that explains every reported form.

The Hessdalen Lights

In a valley in central Norway, unexplained lights have hovered, darted and pulsed since at least the early 1980s. Project Hessdalen, set up in 1983, maintains automated cameras and instruments. Some lights have been identified as cars or aircraft; a remainder are not. Hypotheses include combustion of dust in the air and electrical effects from the valley's mineral deposits.

Cases Science Closed

The Sailing Stones of Racetrack Playa

For decades visitors to Racetrack Playa in Death Valley found rocks, some weighing hundreds of kilograms, at the end of long trails across the flat lakebed. No one had seen them move. In 2014, a team including Richard Norris and James Norris published GPS-tracked observations in PLOS ONE: after rare rain, a thin layer of ice formed on a shallow pond, broke into large panes in morning sun, and light winds pushed those panes and the stones along at a few metres per minute.

The Bloop

In 1997 NOAA hydrophones in the South Pacific picked up an extremely loud, low-frequency sound. Its name and size fuelled talk of unknown sea creatures. NOAA researchers later matched the signal to icequakes, large icebergs cracking and calving off Antarctica.

Lake Nyos

On 21 August 1986, a cloud of carbon dioxide burst from Lake Nyos in Cameroon and rolled down into surrounding valleys, killing about 1,700 people and thousands of livestock. This was a limnic eruption: volcanic gas had accumulated in the deep water until something disturbed the layers. Degassing pipes have been installed since 2001 to release the gas safely.

Tunguska

On 30 June 1908, an explosion over the Podkamennaya Tunguska River in Siberia flattened roughly 2,000 square kilometres of forest. No impact crater was found, which encouraged exotic theories. The consensus today is an airburst of a stony asteroid or comet fragment several kilometres above the ground.