First photograph of a human being

This is a Daguerreotype taken by the inventor of the process, Louis Daguerre, in 1838. It is a view of the Boulevard du Temple in Paris. To achieve this image (one of his earliest attempts), he exposed a chemically treated metal plate for ten minutes. Others were walking or riding in carriages down that busy street that day, but because they moved, they didn't show up. Only this guy stood still long enough—maybe to have his boots shined—to leave an image.

Other primitive forms of photography had preceded this picture by over a decade. But this anonymous shadowy man is the first human being to ever have his picture taken. There is also the very faint image of the bootblack bent over his work.

Odds are neither of them ever knew they were making history that day.

Below is a detail of the photo.

A tip of the Hokumburg Homburg to Fuhrmanator for finding what the same spot looks like today via Google Maps.

What killed the Dinosaurs?

A giant asteroid smashing into Earth is the only plausible explanation for the extinction of the dinosaurs, a global scientific team said on Thursday, hoping to settle a row that has divided experts for decades.

A panel of 41 scientists from across the world reviewed 20 years' worth of research to try to confirm the cause of the so-called Cretaceous-Tertiary (KT) extinction, which created a "hellish environment" around 65 million years ago and wiped out more than half of all species on the planet.

Scientific opinion was split over whether the extinction was caused by an asteroid or by volcanic activity in the Deccan Traps in what is now India, where there were a series of super volcanic eruptions that lasted around 1.5 million years.

The new study, conducted by scientists from Europe, the United States, Mexico, Canada and Japan and published in the journal Science, found that a 15-kilometre (9 miles) wide asteroid slamming into Earth at Chicxulub in what is now Mexico was the culprit.

The asteroid is thought to have hit Earth with a force a billion times more powerful than the atomic bomb at Hiroshima.

Despite evidence of active volcanism in India, marine and land ecosystems only showed minor changes in the 500,000 years before the K-Pg boundary, suggesting the extinction did not come earlier and was not prompted by eruptions.

The Deccan volcano theory is also thrown into doubt by models of atmospheric chemistry, the team said, which show the asteroid impact would have released much larger amounts of sulphur, dust and soot in a much shorter time than the volcanic eruptions could have, causing extreme darkening and cooling.