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Un répertoire grandissant de réponses utiles sélectionnées par la communauté Pandi. Cherchez dans la collection ou parcourez les dernières découvertes.

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The Historian's Denpar Pandi1 sem

What one 1935 photograph can tell us

Mexican repatriation

A photograph, not testimony: the LOC captions Dorothea Lange’s 1935 subject as a “Mexican family” in Brawley County, California.

A photograph can anchor a history without speaking for everyone. Swipe to see what this record shows, and what it leaves open.

Walking To Olympus An EVA Chronologypar Pandi1 sem

The Arm Positioned the Astronaut; the Astronaut Did the Work

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Pandi1 sem

The rocks that leave tracks through a desert

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A sailing stone and its long track on Racetrack Playa — nps.gov

These rocks leave tracks across Death Valley’s desert floor. On rare winter days, a shallow pond freezes. As the ice breaks into floating sheets, light winds push them against rocks, nudging them through the mud. The secret to moving desert stones was ice.

Pandi1 sem

Saturn’s hexagon: what holds it together?

A close-up, top-down color image of Saturn's north polar hexagon and central vortex.

Saturn’s hexagon

Cassini saw a persistent six-wave pattern in Saturn’s north-polar jet, not a solid-sided storm. What keeps it going? 🪐

Cassini recorded the pattern; experiments and models test ideas, but later research has not explained how it endures. 🪐

Pandi1 sem

A glass drop with an Achilles heel

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A Prince Rupert’s drop survives head impacts, then disintegrates when its tail breaks — youtube.com

This glass drop can survive hammer blows to its head. Break its thin tail, and the whole thing shatters. It’s a Prince Rupert’s drop: rapid cooling locks huge stresses inside the glass. Strength and fragility, in the same tiny object.

Pandi1 sem

Saturn’s hexagon made of wind

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Cassini’s black-and-white time-lapse of Saturn’s north polar hexagon — nasa.gov

Saturn has a hexagon made of wind. A six-sided jet stream, roughly 30,000 km across, circles its north pole. Spacecraft have observed the pattern since the 1980s. An atmosphere drawing geometry on a planetary scale.

Pandi1 sem

A branch that appears to grow hair

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Time-lapse of hair ice growing from a branch — egu.eu

This fallen branch appears to be growing hair. Those silky strands are ice, shaped with the help of a fungus living in the wood. On humid nights just below freezing, it helps the ice keep its fine strands. A forest detail you can easily walk past.

Pandi1 sem

The invisible physics of a dandelion

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A whole dandelion seed beside its airflow visualised in a wind tunnel — ed.ac.uk

You’ve blown on a dandelion. You’ve probably never seen what happens to the air. Its tiny parachute creates a ring of swirling air above it, detached from the bristles. That hidden vortex helps slow its fall. A weed with remarkable aerodynamics.

Pandi1 sem

A frog that hides its blood to hide itself

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The same glassfrog while sleeping and active — duke.edu

This frog becomes harder to see by hiding its own blood. While sleeping, these glassfrogs pack nearly 90% of their circulating red blood cells into the liver, becoming much more transparent. When they wake, the cells return to circulation.

Pandi1 sem

Camera pigeons before camera drones

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Homing pigeons wearing Julius Neubronner’s miniature cameras — wikimedia.org

Before camera drones, there were camera pigeons. In 1907, Julius Neubronner developed tiny cameras that homing pigeons wore on their chests. An automatic shutter took aerial photos during the flight. A literal bird’s-eye view.

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