Nell Greenfieldboyce

It was four 4 o'clock in the morning, well before sunrise, and cold. A light wintry mix of rain and snow was falling. The lousy weather was a relief, as it meant even less of a chance that someone might randomly pass by. The small group of scientists didn't want anyone to see what they were about to do.

They'd brought flashlights, a shovel, a trowel, a tape measure, and an old map. The map looked more like a blueprint than a pirate's guide to buried treasure. Still, it did show the secret location of something precious stashed away underground.

More than a billion biological specimens are thought to be stashed away in museums and universities and other places across the United States — everything from dead fish floating in glass jars to dried plants pressed between paper to vials of microbes chilling in a freezer.

Until recently, it's been hard to for researchers to locate all the potentially useful stuff scattered around in storage, even though caretakers say these treasures are like time machines that offer an unrivaled opportunity to understand global change.

Octopuses have alternating periods of "quiet" and "active" sleep that make their rest similar to that of mammals, despite being separated by more than 500 million years of evolution.

During their active periods of sleep, octopuses' skin color changes and their bodies twitch, according to a report in the journal iScience, and they might even have short dreams.

NASA is counting down to what should be the final major test of the massive rocket it is building to put the first woman and the next man on the moon.

In 2016, a family in Illinois thought that a meteorite had hit their backyard. They called up the geology department at nearby Wheaton College to say that whatever struck their property had started a small fire and had left a weird rock embedded in the scorched dirt.

An unopened letter that was mailed back in 1697 but never delivered has been read by researchers who have developed a way to virtually "unfold" sealed letter packets without having to actually break the seal.

The new technique, described in the journal Nature Communications, should allow historians to learn more about "letterlocking," the practice of using elaborate slits, folds, creases and tucks to turn a flat sheet of paper with a written message into a tamper-resistant package.

Updated at 5:40 p.m.

A panel of experts that advises the Centers for Disease Control and Prevention has given its blessing to a new one-shot vaccine for COVID-19.

An ancient, well-preserved tree that was alive the last time the Earth's magnetic poles flipped has helped scientists pin down more precise timing of that event, which occurred about 42,000 years ago.

Tattoo artists in Europe are fighting a new ban on two commonly-used green and blue pigments, saying that losing these ink ingredients would be a disaster for their industry and their art.

A horn made from a conch shell over 17,000 years ago has blasted out musical notes for the first time in millennia.

Archaeologists originally found the seashell in 1931, in a French cave that contains prehistoric wall paintings. They speculated that the cave's past occupants had used the shell as a ceremonial cup for shared drinks, and that a hole in its tip was just accidental damage.

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