In June 1783 a crack opened in the Icelandic highlands and poured out lava and poison gas for eight months. The famine that followed killed a sixth of Iceland, a stinking dry fog spread over Europe, and Benjamin Franklin guessed what it meant.

For 130 years, the kilogram was a golf-ball-sized cylinder locked in a vault near Paris. Then it seemed to start losing weight, and scientists spent four decades learning to weigh with electricity and count atoms to replace it.

In a Montreal operating room, a surgeon touched a wire to the brains of awake patients and asked what they noticed. Their answers gave neuroscience its most famous map, and one of its most stubborn myths.

In 1848 a tamping iron passed through the head of a Vermont railroad foreman. He lived, he changed, and then he quietly got better. The true story of Phineas Gage is stranger than the textbook version.

On March 1, 1954, a miscalculated hydrogen bomb at Bikini rained radioactive ash on Marshall Islanders and a Japanese tuna boat, and changed the nuclear age.

On August 15, 1977, a volunteer circled six characters on a radio telescope printout and wrote Wow! beside them. Nearly 50 years of searches, failed theories and a new look at the old paper later, here is what the Wow! signal was, and what it might have been.

Ranked by erupted magma volume, North America’s five largest eruptions of the past 2.6 million years, from Valles caldera to Yellowstone’s Huckleberry Ridge, and what their calderas and ash beds reveal about how supervolcanoes work.

Death Valley’s 134°F reading from 1913 is still the official world heat record. A new study says the real high was about 120°F. Here is the case against it.

In 1858 a cable under the Atlantic carried messages for three weeks, set New York’s City Hall on fire in celebration, and then went dead. This is how it failed, and how the Great Eastern finally wired two continents together in 1866.

In 1868 astronomers saw a yellow line in the Sun that matched nothing on Earth. The story of helium runs from a forgotten observer in India to a Kansas gas well, a teacup of liquid at Leiden and the helium shortage of 2026.

How two feuding 19th-century scientists, Edward Drinker Cope and Othniel Charles Marsh, bribed, spied and raced to fill America with dinosaurs.

A late moon of Jupiter, a toothed wheel, a mirror spinning 528 times a second and a mile of pipe: the 300-year race to measure the speed of light.

A sickly French road engineer cut away the glass a lens doesn’t need and made lighthouses shine to the horizon. His idea still lights stages, cars and VR headsets.

The deadliest disaster in U.S. history wiped out Galveston in one night in 1900. Then the city built a seawall and jacked itself up as much as 17 feet.