thermodynamics

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.

In the quantum world, a fact becomes objective when its value is imprinted on many independent fragments of the environment, like a notice posted on hundreds of bulletin boards across the city. Each copy alone adds no new information, but it changes the rules of the game for anyone trying to erase that information.

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.

Tea in a cup cools quietly on the table. But if you zoom past at near-light speed, the thermometer will read higher — even though no one heated the tea. Calculations confirm: the needle will creep up. A century ago, physicists split into three camps.

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.

Sugar dissolves in tea, and then with a single motion gathers back into the spoon. In an ordinary kitchen, you won't see that — viscosity and disorder get in the way. But in the world of ultra-slow motions, where inertia vanishes, such tricks become reality.

In a pot of boiling soup, churning currents carry heat to the walls, and the soup cools. In a tokamak, a huge magnetic bottle for plasma, the same thing happens: turbulent eddies carry energy outward, hindering the ignition of a fusion reaction. But sometimes the plasma seems to find a way to calm itself.

A kettle cools on the table. Heat escapes into the air, and is wasted. Yet you could squeeze a bit of electricity out of it. Devices that can do this are called thermomagnetic generators. Inside them, there are no pistons or turbines — only a material that changes its magnetic properties when heated and cooled.

When servers in a data center run at full tilt, they get as hot as a forgotten iron. That heat goes to waste, and cooling them eats up even more energy. Engineers in Germany have proposed putting that heat to work: let it drive liquid through thin tubes all by itself, with no motors or pumps. Their device looks like a flat box with an asymmetric bottom.

A droplet of liquid metal glides along a narrow channel like mercury from a broken thermometer. It needs no motor — the fuel is a chemical reaction with the surrounding liquid. But what happens when the droplet hits a wall? Previously, such machines were studied in open spaces, and in tight channels they behave differently.

A film of a shattered cup played backward looks absurd: shards don't spontaneously reassemble. This intuitive sense of irreversibility is tied to the increase of entropy — a measure of disorder in a system. The second law of thermodynamics states that the entropy of an isolated system never decreases, setting time's direction from past to future.

Ice on a warm frying pan doesn't just melt: it starts to move. A thin layer of water forms beneath it, and the piece glides as if on oil. The speed of this sliding depends on how quickly heat travels through the water film and how steep the incline is.

A pot on a stove receives heat, but not work: the gas under the lid just heats up. But what if the stove is not ordinary, but quantum? Then heat and work can arrive simultaneously, like from an engine that also heats. In a new study, exactly this case is described: a classical system (say, a pendulum or a small mirror) bathes in a quantum environment.

A hot coffee cools by radiating invisible light. To maintain temperature, it must receive exactly as much light back. This silent trade of photons is what we feel as steady warmth.

In a freezer, ordinary water turns to ice, but in living cells, such ice is a disaster: sharp crystals tear membranes apart like needles popping a balloon. Scientists who preserve cells for medicine have learned to avoid this calamity, but each method speaks its own language. A new study offers a common vocabulary — thermodynamics.

Every machine, whether a car engine or a tiny nanocooler, runs with a jitter. Fuel burns unevenly, electrons slip through contacts off schedule, and the power needle on your instruments vibrates slightly. These vibrations are called fluctuations. They are not just noise: they tell you how stable a device is and how much energy it wastes.

Run a current through a wire, and the wire heats up. Anyone who has ever touched a phone charger knows this. Physicists call this heating Joule heating, after James Joule, who in the mid-19th century measured how much heat electricity produces. Since then, the formula has been simple: the greater the resistance and the current, the hotter the wire.

In a hot gas of charged particles — plasma — chaotic electric fields work like a sieve. A slow particle gets surrounded by a cloud of opposite charges, which cancels the external field. A fast one sheds this armor and gets accelerated.

The idea of a expanding universe, proposed by Georges Lemaître, finds an unexpected analogy. Space behaves like a piston in a cylinder: dark energy pushes it, much like steam. The relationship between pressure and volume in this 'engine' is strikingly similar to that of a steam boiler.

Ice cubes in a glass melt, and the water mixes on its own. Many quantum systems behave this way: particles exchange energy, and after a while, order disappears. But if you add a spoonful of honey to the glass, mixing slows down, and in intense cold, the water freezes into glass — without a crystal lattice, but also without flow.

Time is a one-way road: events race forward with no U-turn allowed. The arrow of direction is governed by entropy — a measure of disorder, which only grows in the Universe, like a traffic jam at rush hour. You can clear one intersection, but the overall congestion only gets worse.

Water always flows downhill, and heat from hot to cold. That's what энтропия dictates. But the quantum world finds loopholes. Physicists made light particles interact with hot and cold environments in an uncertain sequence — like a flipped coin that hasn't landed yet.

In 1989, John Wheeler proposed a bold idea: "it from bit," meaning everything that exists arises from information. For a long time, this remained a beautiful metaphor, but now physicists have found a concrete mechanism that turns bits into particles.

Two qubits, quantum bits, two-level systems, glide through hot and cold thermal baths. One moves at 0.8 times the speed of light. At that moment, familiar thermodynamics cracks: a moving qubit senses temperature differently than a stationary one. For it, the cold bath can feel hotter, and the hot bath colder.