virtual particle

In the first moments after the Big Bang, the universe underwent a rapid expansion — inflation. Space stretched faster than light, and quantum jitters of the vacuum turned into real particles. This is how dark matter, the invisible substance that holds galaxies together, could have been born.

A stone falls into still water, and smooth rings spread across the surface. If the stone doesn't just fall but also spins, tiny whirlpools, vortices, appear on the surface. Light can do the same, only instead of water, it's space and time themselves.

Boiling water in a pot is a good place to start. Bubbles of steam rise, pop, and the surface settles down. Something similar might have happened in the first moments of the universe's life with a special field filling space: bubbles of a new phase inflated and collided, like islands of steam in liquid.

Inflate a balloon, and the dots on its surface move apart from each other. Our universe expands in much the same way. The mathematical model of this process is called de Sitter space — where scientists study how the tiniest 'building blocks' of matter, elementary particles, behave. But in a curved, constantly expanding space, the usual description of particles breaks down.

Quantum vacuum is not absolute emptiness. It is more like a taut membrane that constantly ripples from invisible particles popping in and out of existence. Even in total darkness, this membrane trembles. Physicists decided to see how it behaves around a thin spherical shell, inside which is ordinary flat space, like in our room.

Electric charge is not like a number chiseled in stone. In the vacuum around any charged particle, pairs of particles and antiparticles are constantly born and annihilated, like the foam in a glass of champagne. The bubbles screen the true charge, making it appear smaller or larger depending on how close we get.

The quantum vacuum is not a dead void but a boiling cauldron of probabilities. In some theories, our Universe is frozen in a metastable state: like superheated water, it's ready to explode into steam at the slightest nudge.

The void is never truly empty. In curved spacetime (for instance, in an expanding universe or near a black hole) the vacuum heats up. This is reminiscent of how acceleration makes particles appear seemingly out of nowhere: a phenomenon known as thermal vacuum radiation.

After the Big Bang, the universe may have been stuck in a false vacuum — a temporary state like a soap bubble ready to pop. A rare true vacuum bubble could then erupt, stretching space in the blink of an eye.

A builder checks the strength of an arch not by running through all possible shapes in their head, but by mentally nudging it and seeing how much force is expended. That's essentially how the principle of virtual work works in mechanics. The authors of a new study have applied this approach to the very geometry of spacetime. They constructed a covariant framework of virtual work for the metric.

An empty glass on the table seems reliable. But if there's a microcrack in the bottom, one day it will break — not with a crash, but quietly, spreading in a web of lines. So too with the vacuum: it may not be the true vacuum but a false one — temporarily stable, yet ready to transition to a deeper, real state.

In the microcosm, long-range forces, gravity or electricity, do not switch off even at enormous distances. Therefore, any particle drags behind it a trail of soft (i.e., very low-energy) photons or gravitons. This trail is called the "dress"; without it, calculations fall apart and infinities appear.

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.

Astronomers build maps of galaxies and listen to the radio whisper of neutral hydrogen. The signal is so faint that even a working TV would drown it out, but sensitive antennas pick it up from the depths of the Universe.

A superconductor carries current without resistance, like water running through a pipe without friction. The secret lies in electron pairs: two electrons stick together as one, even though they normally repel. In an ordinary superconductor, the spins of the electrons in a pair point in opposite directions: this is the singlet state.

Energy transfer in photosynthesis is like a children's slide: it bends under the weight of one, reshaping the path for the next. That's what happens in a leaf: an excited molecule instantly reshapes the 'landscape' of its neighbors. Physicists reproduce this effect using ions suspended in a vacuum trap.

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.

Quantum nothingness resembles water in a pot just before boiling. From time to time, a bubble spontaneously swells up — but not of steam, but of an entire universe. Such a bubble doesn't collapse; instead, it inflates into spacetime, triggering its own Big Bang. The only question is how often this happens.

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.

When an electric field reaches monstrous strength, emptiness ceases to be empty. Back in the mid-20th century, Julian Schwinger showed that the vacuum literally explodes with pairs of particle-antiparticle if the field is intense enough.

The early universe resembled a rapidly inflating balloon: it expanded so fast that light couldn't keep up with its own edges. Then this frantic acceleration gave way to calm expansion. The balloon was no longer being blown up, and it began to slowly deflate. At the moment of the regime change, emptiness didn't stay empty: from it, as if from an overheated boiler, pairs of particles burst forth.

A pot of water has just been stirred: the whirlpools and eddies gradually calm down, and the liquid becomes smooth. A similar process, but in the quantum world, occurs in superfluid helium or in a cloud of ultracold atoms.

A handful of rice grains falls onto a hot skillet, and they start jumping. Each grain pushes its neighbors, and the whole pile stirs without any external hand. That's active matter: a multitude of particles that draw energy on their own and convert it into motion.

According to the Standard Model, the vacuum is not emptiness but an ocean of virtual ghost particles. An ultra-strong electromagnetic field, like a storm, yanks electron-positron pairs into reality.

A deuterium molecule, two atoms of heavy hydrogen, falls apart under a laser pulse. One electron is ripped away, leaving an ion behind. At that moment, they are still linked: the direction of one immediately tells you which way the other went. This link is called quantum entanglement.

Vacuum is not silent emptiness, but a boiling cauldron of quantum fluctuations, born from nothing and vanishing in billionths of a second. This invisible symphony acts like a constant wind, pressing an atom against a wall — as if a powerful bass note pushes a light ball.

The quantum vacuum is not emptiness, but a tautly stretched string, where particles constantly appear and vanish. Abruptly changing conditions, like shifting the mirrors of a microcavity, causes the 'string' to emit real photons.

In helium cooled to near absolute zero, the liquid stops rubbing against itself and begins to flow without any resistance.

In the first instants after the big bang, the universe was a quantum vacuum where pairs of particles and antiparticles, virtual "guests" from physical nothingness, spontaneously appeared and almost immediately annihilated.

A snowdrift grows by strict rules: falling snowflakes form bumps, those attract more snow, and the bumps amplify. The same mathematics describes city growth, patterns on bark, ripples on water, and clusters of cosmic dust. Physicists call this uniformity universality.

Two phones with identical batteries: one charges in a basement with a weak signal, and the process goes slower. The battery percentage here plays the role of a clock hand. Physicists applied the same logic to the quantum world. Their clock is a microscopic battery that stores energy. The charging rate depends on a hidden quantum 'mode'—like a switch.

A spring compressed to the limit breaks. Likewise, classical gravity theory leads to a singularity — a point where all laws break down. Quantum mechanics turns this end into an elastic bounce.

A laser beam holds a single ion in a vacuum, and that ion behaves like a ball trapped between two cups. The cups aren't pits in the ground but regions where the ion energetically prefers to be. In the classical world, a ball would roll into one cup and stay there.

Liquid helium at ultra-low temperatures enters a state of superfluidity: it flows without friction, like a perfect lubricant.

In the first instants after the Big Bang, the Universe expanded faster than light could cross it. This rapid growth, inflation, stretched tiny quantum jitters to the size of entire galaxies. But from what state did these jitters begin?

In a container the size of a coin, light behaves like water: it gathers into a single quantum fluid. When energy is added, whirlpools, quantum vortices, spin up on their own. Each vortex is like a tiny whirlpool that cannot simply disappear. Physicists illuminated this fluid with a laser and took snapshots.

Two metal plates in a perfect vacuum attract each other. Even Richard Feynman compared emptiness to a boiling foam: particle pairs are born and immediately vanish, creating the Casimir effect. If the plates are asymmetric, they also start to twist — that's a vacuum motor. But rotation doesn't require oddly shaped parts.

In a glass of salty water, even if it sits perfectly still, something is always happening. Tiny salt particles, ions, float and collide, sending ripples through the water. These ripples are invisible, but they create a force that attracts or repels nearby objects. Previously, it was thought that this force only acts over very short distances, as if it quickly fades out.

Our Universe may have arisen from a highly unstable state that physicists call the false vacuum. Imagine a glass of water cooled below its freezing point: the liquid remains liquid only until the first jolt, which instantly triggers crystallization into ice.

Quantum entanglement is a special connection between particles: they affect each other instantly, even across light-years. For a long time, it was believed that strong acceleration destroys this bond.