direct waves

The mirror races along at nearly forty thousand kilometers per second. Light that strikes it bounces back, but changed, like a ball volleyed by a racket in mid-swing. That's exactly the kind of mirror scientists have built inside an ultra-thin glass thread filled with hydrogen. First, a powerful laser pulse is sent down the fiber.

Drop a pebble into a pond, and ripples spread across the water. Something similar happens when a black hole merges with another: it emits gravitational waves that resemble the fading ring of a bell.

A stone drops into a pond, and ripples spread across the water. In the same way, massive bodies generate gravitational waves, except it's space itself that ripples. So far, these waves have been caught by giant detectors that barely flinch as a wave passes through. But what happens on the microscopic scale, inside a tiny piece of matter?

When a star many times heavier than the Sun dies, it collapses and explodes as a supernova. This is not just a flash of light — the entire process, from core collapse to the ejection of the outer layers, makes space itself tremble. These ripples are called gravitational waves.

A thrown stone sends ripples across water. A gravitational wave is the same kind of ripple, but in spacetime. It is produced, for example, by the merger of two black holes. In classical physics, this ripple is eternal: once created, it travels through the Universe without fading.

In the first moments of its life, the universe resembled a boiling cauldron. Matter wasn't spread evenly — clumps and voids were brewing within it, and their violent motion gave rise to a trembling of space itself: gravitational waves.

In the first 10⁻³⁵ seconds after the big bang, the most rapid part unfolded. Space expanded faster than light — that's expansion of the universe (inflation). Almost the entire score was performed by a single field, the inflaton, conducting the tempo and key.

A thousand years ago, Vikings took Iceland spar to sea. The translucent crystal split light into two rays. By their brightness, they could find the sun even in fog. Birefringence — the physical term for this phenomenon — now helps hunt for the most elusive force in the cosmos.

The spiral of water draining into a sink spins faster and faster toward the center. In an ordinary black hole, that funnel ends in an infinitely sharp point — a singularity where the laws of physics break down. But this new work considers a different picture: the funnel doesn't taper to a needle but ends in a smooth, swelling bubble.

Space is full of invisible waves — ripples in the fabric of spacetime left behind by cataclysms like black hole mergers. An ordinary black hole swallows everything without a trace. But there are hypothetical exotic objects — ultradense clumps of matter without an event horizon (a surface from which not even light can escape).

In the first moments after the Big Bang, the Universe hummed like a bell. Inflation, the epoch of rapid expansion confirmed by measurements of the cosmic microwave background, ended, and the inflaton field began oscillating around the minimum of its potential.

When two black holes merge far away, we receive a tremor of space — gravitational waves. Usually, they are described by Einstein's equations, but what if gravity works differently at the tiniest distances? The authors took one such hypothesis — Hořava–Lifshitz gravity.

The Universe is humming, but our ears catch only the bass. LIGO hears the rumble of black hole mergers — the infrasound of space. Higher up, in the gigahertz range, the flutes and violins of primordial gravity ring out.

The LIGO detectors caught the signal GW250114—a gravitational wave from the merger of two black holes. After the main burst, a decaying 'tail' remained — direct waves from the newborn hole's horizon. It was expected that their damping would reveal the gravitational strength at the horizon's surface. But the measured value came out smaller.

Two ultradense spheres, each the size of a city, whirl in a dance. Their masses are less than the Sun's, but inside them is matter compressed to unimaginable limits. One sphere is a neutron star; the other is a strange star, made entirely of quarks — the elementary particles that build up protons and neutrons.

The merger of two black holes is not just a silent dance, but a grand act after which spacetime itself vibrates for a long time. These damped oscillations — quasi-normal modes — are like the ringing of a gigantic bell. But there is another echo: barely perceptible, almost ghostly.

In the ocean of space, every storm of birth or merger of supermassive black holes generates ripples — gravitational waves traveling at the speed of light. Over billions of years, these waves superimpose, merging into a low-frequency hum, like a distant surf.

Traditionally a black hole was described by three parameters — mass, charge, and angular momentum.

The mystery of dark matter has puzzled physicists for nearly a century. Among the candidates for its role are primordial black holes (PBHs), born in the fiery embrace of the first moment after the Big Bang.

The cosmos sets its own lenses in the path of gravitational waves. When two black holes merge, the resulting ripple travels through the universe. If it encounters a massive galaxy cluster along the way, its gravity bends the path of the waves — much like glass focuses light.

Two neutron stars, ultra-dense remnants of massive stars, merge into one, and the space around them shudders: a gravitational wave is born, a ripple in the very fabric of spacetime. Almost simultaneously, a narrow stream of matter, the jet, erupts from the scene.

A black hole, like a spinning wheel, twists a cloud of light particles, axions, around itself. These particles are the leading candidates for dark matter. The cloud follows the laws of quantum mechanics, resembling a giant atom: there are levels, and there are transitions between them.

At the center of attention is a black hole with two points of no return: the outer and inner horizons. Beyond the outer horizon, space and time swap roles, but the journey is not over. Further in, at the inner horizon, gravity has another surprise in store.

When two superdense stars circle in a tight dance, the space around them shudders. This shudder, gravitational waves, is caught by giant detectors on Earth. But deciphering the signal is tricky: you need to figure out what exactly you're dealing with — a pair of black holes or neutron stars.

Two heavy spheres of dark emptiness hurtle toward each other and collide dead-on. This is not billiards: it's the collision of two equal black holes. The impact sends a tremor through space itself — gravitational waves. Most of this tremor is a low hum that physicists call bremsstrahlung.

Two stones fall into a pond. Ripples spread from each, but when they collide, there's a splash and a short, sharp clap. That's roughly what the merger of two neutron stars sounds like: those ultra-dense remnants of exploded stars.

Drop a pebble into a pond — ripples spread across the water. In much the same way, a massive body circling a black hole perturbs the fabric of spacetime, generating gravitational waves. But what if the pond itself isn't flat, but has hidden folds — extra dimensions invisible to the eye?

The merger of two black holes is the most powerful explosion in the Universe, yet we cannot see it. We only catch the shudder in spacetime — gravitational waves that carry information from the heart of the cataclysm. In December 2025, the LIGO detectors registered event GW250114.

In the usual picture, a black hole is a featureless pit in spacetime. But if a shell of matter vibrates around it, the gap between the edge of the abyss and this shell becomes a resonant cavity.

Two burned-out stars, each about the size of Earth but heavier than the Sun, spiral ever closer until one crashes into the other. The impact triggers a thermonuclear explosion, giving birth to a type Ia supernova. Such flashes serve as cosmic beacons for measuring distances across the universe. Yet the details of their origin remain hotly debated.

A giant black hole tore apart a star, leaving behind a lopsided disk of scorching gas — like a vinyl record warped by the heat. Now a tiny black hole (or a star) zips around and repeatedly pierces that disk. Each puncture is a bright X-ray flare.

A giant drum has just taken a hit. Its membrane is still trembling, but besides the main boom, a fine ripple spreads across it — someone ran a finger over the taut skin. In much the same way, in the first moments after the Big Bang, spacetime vibrated not only with the "roar" of expansion but also with the tension of suddenly emerging magnetic fields.

Usually, black holes inch closer gradually, circling in a tightening spiral. This dance births a long ripple of gravitational waves — a tremor in the very fabric of spacetime. Detectors LIGO and Virgo routinely catch such mergers. But GW190521 is the exception.

When two black holes merge, they shake the very fabric of spacetime. The newborn giant doesn't settle instantly (it rings like a cosmic bell, emitting a characteristic pattern of damped gravitational waves) the so-called ringdown.

When a neutron star and a black hole merge, they send out gravitational waves — ripples in spacetime that reach Earth. These ripples carry the imprint of their final dance: the orbit before the collision is often elongated, like an ellipse.

A stone falls into a pond — ripples spread across the water. If the stone doesn't fall but whizzes over the surface at tremendous speed, a straight wave runs along the water. When it hits a floating log, ripples spread out from the point of impact. That's roughly how gravity works in the new study.

A black hole collision isn't just a burst of gravitational waves; it also leaves a lasting trace: an eternal curvature of spacetime — gravitational memory. Like a boat on water leaves a lingering wake, the cosmos 'remembers' the catastrophe.

The fabric of space bends under weight, like a stretched trampoline. Gravitational waves — ripples spreading from cosmic cataclysms, such as merging black holes. If such a ripple encounters a massive galaxy or invisible dark matter, they act like a magnifying glass: bending and amplifying the signal.

The term 'wormhole'—coined for physics by John Archibald Wheeler in 1957—still teases the imagination. It's a hypothetical tunnel through curved spacetime, connecting distant regions of the Universe or even different universes.

A huge orchestra is tuning up before a concert. Each instrument makes its own noise, and in the general hubbub it's hard to pick out individual sounds. But if the conductor gives a special flick of the baton for a second, all the violins will simultaneously hit one high note, and that pure tone will cut through the cacophony.