waste heat

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.

Hot water after a shower, warm air from ventilation, the heated walls of an engine — all this is heat below 100°C. Usually, it dissipates without doing any useful work. Now it can be captured and turned into electricity. Inside the new device is a wire made of a nickel-titanium alloy. This material remembers its shape: when heated, it contracts; when cooled, it returns to its original shape.

Space is expanding, and that expansion is accelerating. But what if, in the first instants after the Big Bang, gravity behaved differently? The authors of a new study added an invisible field to Einstein's equations that siphons energy from ordinary matter and radiation.

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.

Imagine water as a ballroom, where each molecule is a dancer, constantly forming fleeting partnerships. These hydrogen bonds give rise to local patterns: some resemble a stiff waltz — an ordered network with cavities (low-density structure), others a wild jitterbug, where partners crowd into chaotic dense clusters.

Every year, the food we eat costs humanity tens of millions of years of life due to unhealthy diets. At the same time, a third of all greenhouse gases warming the planet are produced along the journey from farm to plate. It seems obvious: switch to healthier eating, and we'll save the climate and improve our health. But new research shows these two goals don't always go hand in hand.

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.

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.

An ordinary heat engine is like a mill between the hot and cold banks of a river: the greater the drop, the stronger the current. Here, the drop is tiny, just one or two degrees, but water can still turn the wheel. The secret is that water is made to boil not by heating but by a sudden drop in pressure, so steam bursts out even from barely warm liquid.

Any device, from a toaster to a smartphone, heats up when operating. This is the inevitable result of energy conversion — there's always a heat trace left, like a hot stove burner after cooking.

Water in a glass settles down once you stop stirring it. Oil in an engine dampens vibrations. It seems viscosity is always about damping. But in some flows, it's the opposite: add friction, and waves start to grow as if from nowhere. Physicists have found a simple explanation.

Heat flow usually evens everything out: hot things cool down, cold things warm up, and in the end you are left with a uniform warm swamp. The same holds in the quantum world: the environment, whether a crystal lattice or a gas of photons, tends to destroy the fragile entanglement between particles.