In 1904 Clever Hans tapped out sums for Berlin crowds and stumped a panel of experts. Oskar Pfungst found the horse was reading questioners’ tiny head movements, and the Clever Hans effect still shapes dog research and AI.

Rats from a 1918 shipwreck wiped out Lord Howe Island’s giant stick insect. In 2001 climbers found a few survivors on Ball’s Pyramid, and Melbourne Zoo has since hatched more than 14,000. Now the island is rat-free and deciding whether to bring them home.

A viral post called a patch of ocean the Area 51 of the sea. It isn’t. But some Pacific islands really are off-limits, for reasons from unexploded bombs to rare stick insects.

For four decades, Piltdown Man sat in Britain’s story of human evolution. It was an orangutan jaw and human skull pieces, stained and filed to deceive. Here is how the fake was made, why experts believed it, and how science caught the forger.

He quit school at 14, drove mules up Mount Wilson and joined the observatory as its janitor. Then Milton Humason measured the galaxies that showed the universe is expanding.

In late 1932, a Western Australian wheat belt facing ruin called in the army against some 20,000 emus. Two Lewis guns, thousands of rounds and one baffled major later, the birds were still winning.

In July 1942 six P-38 fighters and two B-17 bombers came down on the Greenland ice cap, and every man walked away. Fifty years later, a team melted a shaft through 268 feet of ice to bring one of the fighters back up. Here is how the Lost Squadron vanished, and how Glacier Girl flew again.

In 1806 a Boston merchant shipped a cargo of pond ice to Martinique and lost his shirt. Within decades Frederic Tudor’s ice was reaching Havana, New Orleans and Calcutta. Here is how the frozen-water trade rose, changed how the world drinks, and melted away.

About six million years ago the Mediterranean was cut off from the Atlantic and nearly dried up, leaving a desert of salt kilometers below sea level. Here is how a drill ship found it, the flood that refilled the sea, and the architect who wanted to lower it on purpose.

In the autumn of 1917, British schoolchildren were paid to gather horse chestnuts by the ton, and nobody would tell them why. The conkers were bound for a secret factory that fermented them into acetone, the solvent behind the cordite that fired British guns. Here is how the scheme worked, why it fell short, and how children in America and Germany were put to similar work.

For about a century, cities from London to Paris to New York moved letters and telegrams through miles of pipes under their streets, pushed by compressed air. Here is how pneumatic tube mail worked, what it carried, including one very unhappy cat, and why trucks won in the end.

In 1938 Lise Meitner, a refugee in Sweden, worked out with her nephew Otto Frisch why uranium had split in two. Hahn alone got the Nobel Prize. Nominated 49 times, she never won, but her name is now on the periodic table.