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Pacific aurora

In 1962 the United States detonated a nuclear bomb in outer space over Hawai’i. It caused an artificial aurora in the sky over Honolulu – and another one over Samoa, more than four thousand kilometres away.

Where the tides turn

Amphidromic points

How high does the high tide go? In the Bay of Fundy, Canada, the difference between high and low tides is more than 16 metres. But at several points in the world’s oceans, called the tidal nodes, the sea level doesn’t change at all.

Largest ocean current

Southern Ocean

How do you measure ocean flow? One sverdrup equals a million cubic metres of water per second. All of the world’s rivers emptying into the ocean is 1.2 sverdrups; the largest current in the world is more than a hundred times larger.

Underwater unknown

Paleodictyon

A strange honeycomb pattern appears on sea ridges around the world. We think that it is created by living creatures, but no-one has ever seen one. Oh, and there are fossils of the patterns going back 500 million years.