scalar charge

A boiling kettle on the stove eventually boils dry — and so, according to the classical picture, a black hole should gradually vanish in a hiss of radiation. But what if you add a special ingredient to the kettle?

A scale that weighs not a body, but the very space around it. That's how Einstein's equations work in general relativity: they link the curvature of spacetime to what resides within it.

A black hole is not a vacuum cleaner. By itself, it doesn't pull everything in more strongly than an ordinary star of the same mass. But if there's a magnetic field nearby and charged particles flying around, an interesting game begins.

Inside the atomic nucleus, protons and neutrons are packed so tightly that the forces between them resemble tightly coiled springs. Some springs compress and expand equally in all directions: these are the familiar central forces.

Two houses with identical facades. Windows, doors, wall color — everything matches. But inside, one is empty, while the other buzzes with life. How can you tell without stepping inside? In space, there's a similar puzzle: a black hole and a gravastar look the same from the outside, but they are built differently.

Light from afar bends around a black hole like a cyclist taking a sharp turn. Get closer, and it starts looping around an invisible sphere of photons. Every black hole has such a sphere, but usually it's wobbly: the slightest nudge sends light flying away or falling in.

A pendulum in a noisy room is constantly jostled by people passing by. Its motion is a mix of regular swings and random jerks. Something similar happens with weak gravitational waves against the backdrop of an expanding universe. In Einstein's general relativity, these waves are tiny ripples in spacetime.

Usually, a black hole is described as a frozen frame: there's mass, there's charge, and it's all static. But real objects live in time. They radiate, lose energy, and change.

In the centers of many galaxies slumber supermassive black holes, surrounded by accretion disks and the activity of active galactic nuclei. When a compact object — such as a stellar-mass black hole — orbits them, a gravitational duet is born.

A black hole merger is not a silent impact. The newborn hole quivers and decays, emitting gravitational waves — ripples in space itself. This signal is called the 'ringdown,' and it resembles the fading chime of a bell: it has a fundamental tone and several overtones.

The explosion of a distant supernova told us something hard to believe: the universe is expanding faster and faster. The engine of this acceleration is dark energy — nearly 70% of everything that exists.

A wormhole is a tunnel connecting two distant regions of the universe. If such a wormhole existed and were traversable, a particle inside it would feel not only gravity but also a force from its own electric field. This force depends on how spacetime is curved around it.

When massive bodies accelerate (say, two stars orbiting each other) the space around them doesn't stay calm. It trembles like the surface of a pond after a stone is thrown. These tremors are called gravitational waves. They carry energy away, and the source gradually loses mass.

A neat stack of atomic layers lies on a substrate. An invisible beam of terahertz light shines down on it, with a magnetic field applied from the side. After reflection, the beam's polarization rotates slightly.

The Sun is not just a source of light but a giant laboratory where ghostly particles are born. Every second, billions of neutrinos fly through your body, barely noticing you. But inside the Sun, these particles behave differently: they change their type on the fly, like an actor playing three roles in a single play.

Quantum noise, like the hiss of an untuned radio, filled the infant Universe. Alan Guth showed that superfast expansion (inflation) caused this ripple to freeze, giving rise to clumps of matter — the seeds of galaxies. A new method extends this picture to any theory of gravity.

An inflating balloon starts out slowly, then suddenly expands faster and faster, as if someone is pumping it up from inside. That's roughly how our universe behaves: galaxies are receding with acceleration. The culprit behind this acceleration is called dark energy.

Right after the Big Bang, space swelled at an unimaginable speed — that's inflation. Now expansion has slowed, but galaxies are moving apart faster and faster. The culprit behind the acceleration has been named dark energy.

In the 1920s, Edwin Hubble noticed galaxies were moving apart — thus discovering the expansion of the Universe.

On the table sits a glass of water. For each molecule, all directions are equivalent: it doesn't distinguish north from south. That's symmetry. But if you freeze the water, the molecules align into an ice lattice, and symmetry breaks: a preferred direction emerges. The quantum world breaks symmetry more cunningly. The glass freezes, yet each molecule still tumbles randomly.

A palm hovering over a hot stove feels the heat even when the surrounding air seems cool. Something similar happens to electrons in the Aharonov–Bohm effect: the particle senses an electric voltage even though it enters a region where the field has already been switched off.

If you drop an ice cube into a glass of water, it will float until it melts. But if you cool the water slowly, at some point it all freezes at once: that's a first-order phase transition: abrupt, with a clear boundary.

A stone thrown into a pond creates ripples that spread far. But if you throw it into thick jelly, the waves die out almost immediately. That's roughly how an additional gravity field behaves under different mathematical descriptions. The authors built a unified approach to calculate how such a field manifests itself in the Solar System.

Take two heavy balls and place them a meter apart: they attract each other with a force that weakens by a factor of four when you double the distance. Newton discovered this law, and it works in a room, in the solar system, in a galaxy. But does it still hold when we're talking about hundreds of millions of light-years? Astronomers found a way to test this directly.

In its first moments, the Universe expanded faster than light could cross it. This process, inflation, left behind ripples — tiny density fluctuations from which galaxies later grew. The spectrum of these ripples is usually described by a number: if it is exactly 1, then all fluctuations, large and small, were equally strong.

In the dark depths of space lurks invisible matter. It doesn't shine, but its pull holds galaxies together. Usually, we assume dark matter obeys the same laws of gravity as tables and chairs. A new study offers a different perspective: dark matter might subtly alter gravity itself.

A stone on a table won't budge without a kick. Where does this stubbornness come from? The idea that the rest of the Universe is to blame was put forward over a century ago. Now it has been formalized into a rigorous theory. In the new work, gravity is described not as an attraction between bodies but as a field that sets the scale of distances and time.