liquid water

In a Paris laboratory, light was made to flow around an obstacle the way water flows around a rock in a stream. But this water is special: it feels no friction.

Every Martian night, salt crystals on the planet's surface soak up moisture from the thin air, much like a sponge draws water from a damp cloth. By morning, a microscopic brine accumulates inside them, and during the day, as temperatures rise, that brine finds itself trapped in tiny cavities.

Swimming season opens when the water feels tolerable. But everyone has their own threshold: one person shivers at twenty degrees, another swims comfortably at fifteen. Scientists decided to figure out where this difference comes from. They compared a swimmer's body to a house trying to keep heat in while a cold wind blows outside.

If you push water in a narrow channel too fast, a steep wave forms and breaks into foam. In the world of ultracold atoms, cooled to near absolute zero, quantum laws prevent such a wave from breaking. Physicists took a cloud of rubidium atoms stretched into a thin thread and sharply compressed it from one end with a movable wall of light.

A proton beam aimed at a tumor cuts through soft tissue like a knife through butter, but its range depends on the subtle properties of water, the stuff we're mostly made of. Water is the body's main component, and how quickly protons slow down in it determines exactly where they deposit their energy.

A raindrop falls on glass and flattens into a pancake. Add a bit of polymer to the water, and it becomes elastic, like jelly. You'd think such a jelly would spread differently.

A cluster of glowing dots drifts through the darkness, now compressing into islands, now spreading out in waves. These are not fish or birds: this is a mathematical model of active matter, where each particle spends its own energy on movement, and also is born, dies, and competes with neighbors for space.

A night river is dotted with tiny sparks. This isn't plankton: it's functional pollen-sensors, millimeter-sized devices that swim on their own and measure the water's chemistry. Each particle is a tiny lab. Inside, two reagents meet: one triggers a glow upon contact with a pollutant, and the second, a colored filter, blocks out interference.

Soil is not a solid sponge but a labyrinth of pores of various sizes. After rain, water does not fill them all at once: first the narrowest ones, then the wider ones. Physicists built a theory of this process based on a simple image — a set of communicating vessels.

Water is not just a wet substance. On a picosecond scale, it resembles a dance floor where molecules continuously break and form bonds with each other. Usually, this dance is described by one main movement — collective relaxation, as if the whole crowd simultaneously slows down after the music stops.

In the new model, each active particle has an internal rhythm: it spins either left or right. Chirality is key: some twirl clockwise, others counterclockwise. But when such a particle bumps into an obstacle or a neighbor, it flips its spin, like a figure skater who, after touching the board, explodes into a reverse pirouette.

In the first moments of its life, the Universe resembled a boiling cauldron. As it cooled, phase transitions occurred — much like steam turning into water, but instead of molecules, the very state of space changed. In this cauldron, bubbles of the new phase were born, akin to bubbles in a pot coming to a boil.

If you squeeze water between two glass plates so that only two layers of molecules fit, it becomes something between a liquid and ice. At room temperature, molecules in such a trap still move but arrange themselves into a semblance of a crystal lattice.

Imagine two immiscible liquids, such as oil and water. Under normal conditions, they tend to separate, forming a clear interface. But introduce microscopic swimmers (bacteria, whose basis is carbon) and the picture changes dramatically.

Billions of tiny motors hum inside every living creature. Cells ceaselessly pump substances, burn sugar, and build new proteins, and all this invisible motion warms us from within. To maintain order, life must dissipate heat into the environment, like a stove that never goes out. The power of this internal heating is almost independent of size.

Millions of cilia, thin hairs, work inside the tiny ducts of our bodies. They beat in synchrony, like the oars of a galley, pushing viscous mucus or fluid along. The authors of a new study propose viewing the ciliary carpet as an active porous medium — something like a sponge that squeezes and releases itself, driving water through.

In a crystal of water and caustic cesium, oxygen and cesium atoms sit in place like beads in a rigid lattice. Hydrogen atoms behave differently: they are like passengers constantly changing seats. In this layered material, each oxygen is linked to three neighbors via hydrogen bridges, forming a honeycomb-like pattern.

A drop of water on a table usually sits still. But make the table slightly softer on one edge and stiffer on the other, and the drop will crawl toward the stiffer side. This phenomenon is called durotaxis: the liquid itself chooses where to flow, without pumps or electricity. This trick works because the surface under the drop is not uniform.

A tiny oil drop squeezes through a water channel narrower than itself. In pure water, it crawls along calmly, like a round bead. But add a little soap to the water, and the drop begins to bend, like a caterpillar.

At the Large Hadron Collider, not only nuclei but also individual protons collide. Even in such small systems, collective behavior resembling the flow of a liquid is observed. But the proton is a quantum object; its state is described by a wave function, not by temperature and pressure.

A raindrop falls into a puddle, and the impact sends up a little fountain of fine spray. Each of those droplets is a new, secondary drop. How many there are, how big they are, and how long they live depend on a host of factors: the fall speed, the drop size, the properties of the water. Scientists set out to make sense of this chaos using computer simulations.

Inside a cell, there are tiny liquid droplets, like oil droplets in water. They form from proteins and RNA and serve all sorts of purposes, from storing molecules to speeding up reactions. But if droplets start merging with each other, you'd end up with one big puddle, which would wreck the cell's organization.

A plastic heart rests on the water and doesn't tip over, no matter how you turn it. It freezes in any position, as if the water were holding it by invisible strings. This trick is possible thanks to the Zindler curve — a shape in which all lines that divide the area in half have the same length. The Zindler curve is a closed curve where any chord that bisects the area has the same length.

Water is the only common liquid that doesn't immediately contract when cooled. Ice melts, and water becomes denser, but only up to 4 degrees Celsius. Beyond that, with further cooling, it expands again. This quirk explains why fish survive in freezing ponds: the densest water sinks to the bottom, while a lighter cold layer stays on top and turns into ice.

A membrane for water electrolysis is like a sponge soaked with water. Inside it, hydroxide ions, particles that carry electric charge, must move freely. But exactly how they move has long been a mystery: tracking each ion in an experiment is too difficult.

Hydrogen is a champion in energy per kilogram, but storing it is a hassle. As a gas, it takes up a huge volume, and if you compress it or cool it to a liquid, you need heavy tanks and lots of energy. There's a third way: some solid materials absorb hydrogen like a sponge soaks up water and hold it within. Heat it up, hydrogen comes out; cool it down, it gets absorbed back.

The layer of cells lining internal organs is like a crowd in a packed subway: everyone stands shoulder to shoulder, but sometimes the crowd starts to flow, and people slip past each other. Biologists call this behavior a transition from a jammed, solid state to a fluid one.

The lymphatic system is like a city's network of canals, through which water slowly moves, carrying away waste from tissues. But it has no single pump-heart. Instead, along the vessels are placed small station-locks — lymphangions. Each such lock squeezes itself like a fist and pushes fluid onward. How they coordinate their work has long remained a mystery.

Two liquid droplets hanging side by side begin to sing in unison. One droplet is like a string tuned to a certain pitch, and together they form a laser that shines with a single, pure color. That's how a new type of sensor, a liquid photonic molecule, works. The secret is that the droplets are slightly different in size.

An ordinary wire heats up when current flows through it. A superconductor doesn't. But almost all known superconductors require either very low temperatures or enormous pressures, like those deep inside planets. Scientists have long searched for a material that avoids these extremes.

Deep beneath us, hundreds of kilometers down, lies a layer that can absorb water like a sponge. The minerals there, wadsleyite and ringwoodite, can hold up to 1–2% water by weight within their crystal lattices.

A distant red object usually means one thing: we're seeing a dust veil over a scorching disk falling into a black hole. But when the James Webb split its light into shades, a shadow appeared inside — just like steam from boiling water intercepts rays.

The diffusion equation, a mathematical tool describing how particles spread out in space, has long painted a paradoxical picture: a disturbance, like ripples on Water, instantly engulfs the entire universe. This challenged the theory of relativity, which holds that nothing can move faster than light.

Salt in a glass of water is a crowd of charged particles. When there's plenty of water, each particle floats on its own, wrapped in a thick fur coat of water molecules. But as you keep adding salt, the water runs out for everyone, and the particles start seeking each other out. First, they stick together in pairs, then in larger clumps.

A sheet of paper released from a window flutters, tumbles, and sometimes pauses flat for a second. Until now, to honestly predict such behavior, you had to run millions of equations on supercomputers for every drop of air. That's like simulating every atom of a cash register to count change at a store. The new approach is smarter.

A drop of oil in water behaves like a tiny ball: it seeks the spot with the least energy. If a wall is nearby, the drop often sticks to it, just as a raindrop spreads on glass. In a mixture of two immiscible liquids, such as polyethylene glycol and dextran, tiny droplets of one liquid form inside the other.

Water is the gold standard for life. We search for its traces on Mars, in icy moons, and in the atmospheres of distant planets. But what if life doesn't need water? On a warm rocky exoplanet with a thin atmosphere, water would evaporate within hours.