spacetime emergence

Clocks in the Universe are tricky things. Usually, in calculations of the birth of the world, a special scalar field plays the role of a clock — something like an invisible fluid filling all of space. It ticks, and physicists watch how the world changes relative to that ticking. But these clocks are man-made, introduced for convenience. The authors of the new work took a different path.

In the quiet of the quantum world, there is no emptiness. Particles are intertwined by invisible threads — entanglement. The authors of the work proposed that the very fabric of spacetime is woven from these threads. This is not just a metaphor: they built a mathematical framework where the distance between points is determined by how much shared information they hold.

In a two-dimensional universe, a black hole looks like a funnel in spacetime. But the authors of the new work went further: they proposed that the space where particle momenta 'live' is also curved, like a saddle.

At the center of a classical black hole lurks a singularity — a point where the density and curvature of spacetime become infinite. Physics goes silent there.

In the first moments after the Big Bang, the universe expanded at a terrifying rate. This process is called inflation, and it smoothed out all the wrinkles, making the cosmos homogeneous. But what started inflation itself?

A quantum wave is like a long-exposure photograph: everything’s blurred, but the blur itself reveals motion. Usually these frozen waves are treated as convenient abstractions. Yet if at each point in the image you estimate, by brightness, the moment on the particle’s internal clock it landed there, flat space suddenly acquires curves.

When a giant star runs out of fuel, it collapses into a black hole. Such a hole has an outer boundary — the event horizon, beyond which even light cannot escape. But many black holes also have an inner boundary — a second horizon that separates the outer layers from the singularity core.

A translator who translates not words but the very structure of a conversation runs into trouble when the chat moves beyond a quiet room. In a familiar simulation on a spatial lattice, everything follows a strict script. But the moment the interlocutors find themselves in a noisy square, where sound is distorted by echoes and the crowd keeps changing direction, the script falls apart.

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.

In the grand orchestra of the universe, every instrument has its own rhythm. Electrons in an atom make quantum leaps in femtoseconds, neurons in the brain exchange signals in milliseconds, and a human needs tenths of a second to become aware of the 'now.' Physicists have long sought the conductor…

When a grain of sand falls on a table, its impact is predictable. But if you squeezed it down to the size of an atomic nucleus, the familiar laws of gravity would break down — the force of gravity would grow without bound.

Our universe is expanding, and its future, according to cosmologists, is empty, cold de Sitter space. Understanding its quantum nature is like trying to read a book by looking only at its cover. The holographic principle suggests that all information about what happens inside a volume can be encoded on its boundary, like a picture on a film.

A translator hears not just words, but intonation, pauses, the tremor in a voice. Ordinary entropy analysis of cosmic perturbations is like meeting minutes: it records facts but loses the nuances. Pseudoentropy entropy is a new tool that captures the hidden "music" of the early universe.

A billiard game would be strange if the balls had no mass. They wouldn't collide but would pass through each other, ignoring obstacles. That's roughly what it looks like to imagine light as a stream of classical particles — tiny elastic bodies flying in straight lines. A new proof puts an end to that picture.

An orchestra plays out of tune, and the sound seems like chaos. But if you record all the notes and analyze them mathematically, you can reconstruct the shape of the concert hall — where the walls are, how high the ceiling is. Roughly in this way, physicists propose to derive gravity from quantum theory. In everyday life, space and time are the stage on which events unfold.

Time is a fickle thing. Inside a massive star, it flows calmly, like sand in an old clock on a mantelpiece. Outside, on the scale of the entire universe, it stretches along with space, as if the same clock were in an elevator that speeds up and slows down. For a long time, physicists puzzled over whether these two worlds could be glued together without visible seams.

Time in physics is like a conductor setting the tempo for the whole orchestra. But in the quantum world, there's no single baton: each particle can live by its own clock. Usually, we simplify the picture and assume time flows the same for everyone.

Two particles separated by kilometers change their states in concert, as if there were no distance between them. This is called quantum entanglement, and since its discovery it has baffled physicists: no known carrier can travel faster than light, yet correlations appear instantaneously.

Usually, a wormhole is imagined as a tunnel in space, whose walls are held open by something unusual — matter with negative energy. Like the supports in a mine that keep the ceiling from collapsing. But in this work, the physicists did without supports.

Two massive spheres slowly drift apart in empty space. From the standpoint of ordinary mechanics, nothing special is happening. But Einstein's equations say otherwise: accelerating masses stir spacetime itself, and from them spread gravitational waves — ripples that stretch and squeeze everything in their path.

A taut sheet wrinkles. If you tug a corner, a smooth wave runs across; if you sharply bunch the fabric, a sharp crease forms. Space and time in Einstein's equations behave much the same way. Gravitational waves resemble the gentle ripples of the sheet, while shock fronts are like stiff folds where matter's properties change abruptly.

An eternal Universe where the measure of disorder (энтропия) grows is, for most of its time, a homogeneous void. In it, complex structures occasionally assemble by chance, such as fleeting consciousnesses — ‘мозги Больцмана’.

You can zoom into a high-resolution photo for a long time — until suddenly a smooth face dissolves into individual pixels. Something similar, according to a new study, happens to spacetime itself. The authors propose that tiny intervals of length are not pre-existing 'parts' of the universe but results of measurements.

An old mechanical alarm clock ticks on the shelf. You hear the steady sound, see the hands moving, and you're certain time is passing. But if you take the clock apart, you won't find a single part labeled "time." Only springs and gears.

Gravity isn’t fundamental: it’s a shadow cast by entropy, the measure of disorder. Back in the 1970s, Jacob Bekenstein and Stephen Hawking found that black holes store disorder on their surface, as if information is smeared across the shell.

A balloon doesn't deflate all at once: first, dents appear on its surface, which run, merge, and finally the balloon shrivels into a point. Domain walls behave in much the same way — thin partitions that divided space in the first moments after the Big Bang.

The deepest equations of physics, like the Wheeler–DeWitt equation, contain no time. Past and future are scrambled within them, like frames on a film reel with no arrow indicating which way to play it. This symmetry is not a flaw but a feature.

The universe is not a solid monolith, but a canvas of countless quantum threads. Spacetime doesn't flow like water, but vibrates like a tapestry in the wind. For a long time, physicists only saw the overall pattern, neglecting the tremor of individual threads.

A translator gets distracted by every rustle in the hall, and a one-hour meeting stretches into two. That's roughly how ordinary quantum mechanics works: a particle evolves in time, while space serves as the stage. But what if we swapped their roles? Then the particle 'moves' through space, and time becomes a static backdrop.

The pendulum of an old clock swings because a spring mechanism gives it a regular nudge. Now imagine a pendulum that decides on its own when to swing, and does so with a steady rhythm, just because the room is warm and there's a slight draft. That's exactly how time crystals behave, born in clumps of light and matter inside a semiconductor chip.

Cosmology has long sought a loophole behind the Big Bang. Inflation, proposed by Alan Guth, stretches and smooths out primordial inhomogeneities, but what lit the fuse itself?

Holography is the idea that everything happening inside a volume can be encoded on its boundary, like an image on a hologram. In physics, this helps connect gravity to the quantum world. But sometimes, the holographic rules fail to assemble familiar spacetime, and scientists are looking for where exactly the mechanism breaks down.

In one model, spacetime is a smooth lake, and quantum particles are fish swimming in it. Their motion inevitably creates ripples. The math insists that the water trembles — otherwise the theory collapses. This trembling is strictly ordered and comes in two types.

The universe abhors monotony. A century ago, Edwin Hubble and Georges Lemaître gave us an elegant picture: an expanding cosmos, smooth as the surface of an inflated balloon.

A stone falls into a pond, and ripples spread across the water. They reflect off the shore, overlap, and die out. All this motion unfolds in space. But what if the pond itself changed its depth or density for an instant — not at one point, but everywhere at once? A temporal boundary is exactly such a jump in properties over time, not space.

At the heart of an active galaxy, where interstellar gas spirals into a dazzling accretion disk around a supermassive black hole, a boundary is born through which even sound cannot break. This acoustic horizon was long considered frozen ripples on water.

A rubber band stretched in different directions behaves differently from a whole sheet of paper. If you pull on an edge, the deformation does not spread evenly but seems to linger in certain spots.

To understand how the universe emerged from the Big Bang, physicists look to Georges Lemaître's idea of expansion, which rests on the laws of Hendrik Lorentz. One daring approach replaces elementary particles with giant tables of numbers — as if instead of the usual roulette balls, you use numbered cards.

If two people look at a city from different hills, their maps don't match. One sees the tower to the left of the river, the other sees it to the right. But both know: it's the same city. That's roughly how our Universe works in this new approach to quantum gravity. The authors suggest distinguishing between two "flavors" of spacetime.

A drop of cream falls into a cup of coffee, and within a minute, the entire drink turns beige. This mixing process can be quantified: how much "stirring" is needed to transform one distribution of particles into another? In mathematics, this approach is called optimal transport, and the measure of effort is the Wasserstein distance. The authors applied this idea to quantum systems.