dark matter curvature

Think of a merry-go-round: the farther you sit from the center, the faster you're carried around. For a long time, astronomers assumed galaxies work the same way — stars at the edges should orbit more slowly than those near the center. But back in the 1970s, it turned out that in many spiral galaxies, the speed of stars barely drops with distance from the center.

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.

A homogeneous, spherical cloud of cosmic dust begins to contract under its own gravity. At some point, by classical laws, it should collapse into a point of infinite density — a singularity.

Somewhere in the center of a galaxy, a black hole is spinning. It doesn't hang in a void — around it swirls an invisible swarm of dark matter particles. Until now, this swarm was described for non-rotating holes, but in reality, holes always rotate.

A rotating black hole is no calm whirlpool. Space around it shudders and rings at the slightest disturbance, like a guitar string after a pluck. These oscillations are described by the Teukolsky equation — a complex mathematical construct that physicists have studied for half a century. Recently, a strange symmetry was noticed in this equation.

Light freezes at the edge of the abyss: that's what the event horizon of an ordinary black hole looks like. But at the center of this abyss lurks a singularity, a point where the laws of physics break down. What if, instead of a point, there were a hard shell? A gravastar is not a black hole.

The Standard Model of particle physics is a catalog of all known building blocks of the universe: electrons, quarks, and others. But it is silent about dark matter and doesn't get along with gravity.

Imagine a pot of boiling water. Toss in a handful of pasta, and it quickly overcooks and clumps into a sticky mess. But in a huge restaurant kettle where the pasta floats freely, each piece stays separate.

In 1956, two radio telescopes at Jodrell Bank stared at Sirius, capturing not an image but the trembling of intensity.

At the center of the Milky Way, shrouded in dust and glare, lurks a supermassive black hole — Sagittarius A*. Around it, like moths around a flame, swarm dozens of guide stars. Two of them, S2 and S38, with eccentric orbits and periods of just a few years, have become the protagonists in testing the fundamental laws of the cosmos.

Picture the early Universe as an unimaginably large bell. Inflation — the era of rapid expansion, dreamed up by Alan Guth, strikes it, sending a wave rippling across the fabric of spacetime.

The world around us is three-dimensional, but perhaps that's just an illusion. Some theories allow for extra dimensions of space, curled up or stretched in special ways. One such model depicts a five-dimensional universe with a "diluted" dimension (called a linear dilaton).

At the center of an ordinary black hole, according to classical ideas, lurks a singularity — a point of infinite density where the laws of physics break down. But some theories, inspired by the duality idea from string theory, propose replacing the point with a tiny 'smudged' region.

In cricket, there's a special delivery — the googly. The ball spins in a way that deceives the batsman. Physics had its own googly: for nearly half a century, mathematicians couldn't make twistor theory work with real gravity. It described 'nice' fields perfectly, where everything twists in one direction. But as soon as an 'awkward' component appeared, the machinery broke down.

In the first moments of the universe's life, there was not even a hint of dark energy — the very force that today pushes galaxies apart ever faster. But if you look deeper, down to the Planck scale (billions upon billions of times smaller than an atomic nucleus), spacetime ceases to be smooth.

An object cannot be a point. At least, not in Einstein's gravity. The equations of general relativity require that the source of the field, matter, be smeared out in space, not concentrated in an infinitesimal volume. Otherwise, infinities appear in the formulas, and a smooth spacetime cannot be constructed.

At the centers of many galaxies lurk black holes — regions with gravity so strong that even light cannot escape. Stars often orbit them, and sometimes one of those stars is a pulsar, a cosmic lighthouse sending out strictly periodic radio pulses. When such a pulsar moves behind a black hole, its signals reach us with a delay.

The hot broth of the early universe cooled unevenly. At some point, bubbles of a new phase began to pop within it, like steam bubbles in boiling water. But these bubbles weren't made of steam; they were made of a new state of matter in which particles of the dark sector clumped into larger lumps. That's how dark matter could have been born.

The black hole paradox has haunted physicists for decades. If a hole evaporates, where does its contents go? Discoveries by Stephen Hawking and Jacob Bekenstein showed that saving the laws of nature requires an unconventional move. Imagine the universe as a woven blanket of invisible threads.

The Universe behaves like a soap bubble swelling in a multidimensional foam. The dark bubble model explains why it's expanding ever faster: the spacetime bubble grows, and its membrane gains a tiny thickness — about a micron, like a bacterium. At such distances, gravity 'blurs' across this thickness and weakens.

Drop a pebble into a pond, and ripples spread across the water. A black hole 'sounds' much the same when matter falls into it or when its spacetime gets a gentle jolt. These fading oscillations are called quasinormal modes, like the tolling of a bell that gradually fades away.

A wormhole is a hypothetical tunnel in curved spacetime connecting two distant regions of the universe and potentially shortening the journey between them.

Light passing by a black hole swirls like water down a bathtub drain. The most intriguing part is the thin ring where rays can orbit forever, neither falling in nor escaping. This is the photon sphere — an invisible boundary that paints the hole's shadow on the sky.

Through the ripples on the water, pebbles at the bottom of a pool look shifted and warped. In a similar way, the gravity of invisible dark matter bends the light of distant galaxies — a phenomenon known as weak lensing.

Just a few hundred million years after the Big Bang, in the ocean of invisible dark matter, giant black holes were already taking shape. They were born from the matter itself — without any help from stars. This mechanism, based on the equations of Lemaître, explains their early appearance.

A black hole isn’t a perfectly smooth ball. Einstein’s theory allows invisible 'hair' — clumps of scalar field — to swarm around it, warping spacetime. The shadow — the dark region from which light can’t escape — was predicted by Penrose in the 1960s.

For nearly a century, astronomers have watched galaxies spin as if held together by invisible mass. Fritz Zwicky first noticed it, and Vera Rubin precisely measured the speeds of stars at the edges.

Back in the 1930s, Fritz Zwicky noticed that the speeds of galaxies in clusters were too high for the visible mass. Later, Vera Rubin confirmed this for individual galaxies.

A dying star is not just fading away. In its final moments, the core, starved of fuel, collapses into itself at colossal speed. Classical gravity leaves no choice: if the mass is large enough, a black hole is born — a region from which not even light can escape.

You are pacing a huge hall in complete darkness. You walk from wall to wall, counting your steps, and suddenly realize that the distances don't add up as they should. It seems as if the floor is not flat but bulging like a hump or hollowed like a bowl. That's roughly what astronomers found when studying distant galaxies and sound waves frozen in the early Universe.

A black hole is not just a dark sphere in space. If there is gas and dust nearby, they swirl into a flat, glowing disk that gradually falls inward. This disk acts like a lamp, illuminating the hole itself, and against the bright background you can see its shadow — a dark silhouette with sharp edges. But what if the disk is not flat but torn into pieces?

When stars at the edges of galaxies rotate faster than calculations based on visible mass predict, standard cosmology invokes the hypothesis of hidden dark matter — invisible substance that reveals itself only through gravity. A new study offers an alternative that requires no new particles.

Einstein's general relativity describes gravity as the curvature of spacetime — much like a heavy weight pressing down on a stretched elastic sheet. Black holes are regions where this curvature reaches extreme values, the deepest "funnels" in the fabric of the universe.

The familiar picture: gravity always attracts. But if a mass is in quantum superposition (that is, in two places at once, like an object in a double-exposure photograph) everything flips. Quantum theory allows a particle to be both here and there in a literal sense: its position is described by a wave function smeared across space.

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.

At the center of our Galaxy lies a supermassive black hole, with stars orbiting around it. Their motion resembles a cosmic dance: some race along elongated orbits, others follow nearly circular paths. If invisible dark matter exists near the black hole, it slightly distorts these orbits, like an unseen hand nudging a star off course.

The third law of black hole mechanics, proposed by Stephen Hawking, forbids a hole from spinning up to its limit in finite time — much like a whirlpool would need an eternity to reach absolute speed. Yet numerical simulations in five dimensions break this rule.

Back in the last century, Vera Rubin discovered that stars on the outskirts of galaxies rotate too fast, as if held by some invisible substance. Since then, dark matter has remained a puzzle. Usually, its origin is linked to new particles or forces. But a new study points to a simpler source — the geometry of space itself.

The night sky is full of stars, but they are only a small part of everything that exists in the universe. Astronomers have long noticed a strange thing: galaxies rotate so fast that they should fly apart, yet they don't. Something invisible holds them together, like invisible threads linking beads on a spinning wheel. This "something" was named dark matter.

In the first moments, the Universe went through a brief but turbulent period — inflation, when it expanded at a colossal speed. This idea was proposed by Alan Guth. At the same time, particles of ordinary matter were born.