pion

A handful of sand in your fist: the grains press against each other, and your hand can't squeeze any further. Ordinary matter behaves similarly. But in a neutron star, compression is billions of times stronger — atoms are crushed, electrons are squeezed into protons, and nearly all space is filled with neutrons.

In a quiet room, you can hear the faintest whisper. Likewise, in the hydrogen atom, the lightest of all, an uninvited guest is easier to spot. That guest could be the Z' boson, a mediator particle of a new force predicted by many unification theories. The Standard Model already has its own mediator — the Z boson.

The 21-kilometer ring near Protvino was once planned to accelerate protons. Today, the same tunnel could host a very different machine — a muon collider. The muon is a heavy cousin of the electron, and that's its strength. On a curve, an electron radiates like a searchlight, losing precious energy. A muon radiates a billion times less.

Imagine a green beam that, passing through an ingenious optical setup, twists into a three-dimensional funnel of light — an optical vortex. At its heart, like in the eye of a hurricane, the intensity drops to zero. It is there that photons disappear.

At accelerators, by smashing heavy nuclei, physicists briefly create a quark-gluon plasma — a state of matter where quarks and gluons are not confined inside particles but are free. For a long time, it was imagined as a gas, but experiments showed it's an almost perfect liquid.

Imagine a perfectly tuned orchestra, where every instrument is adjusted with flawless precision, trying to play in a noisy hall. That noise is quantum gravity — the microscopic ripples of spacetime. It constantly threatens to throw the musicians off.

Two neutron stars (the remnants of dead stars, compressed to the size of a city but weighing as much as the Sun) spiral around each other and eventually collide. At that moment, something between a black hole and a super-powered magnet is born: a field billions of times stronger than that of the most powerful MRI machine.

A drop of cream in a glass of milk. Shake it, and the fat doesn't spread evenly: it clumps into denser blobs that move differently from the rest of the liquid. Quarks inside mesons, tiny particles that live for mere fractions of a second, behave in much the same way. A meson consists of a quark and an antiquark, and they are rarely equals.

The universe is full of invisible substance that governs the movement of galaxies. In the 1970s, astronomer Vera Rubin showed: without dark matter, stars on the outskirts would have long since flown apart. But what it's made of remains unknown.

At first glance, the atomic nucleus is a cramped communal apartment where protons and neutrons (together called nucleons) live by strict rules. Each occupies its own orbit, like electrons in an atom, and on average everything looks orderly.

Two tin nuclei collide at about two-thirds the speed of light. For an instant, a hot, dense cloud forms, and protons fly out in all directions. If you catch pairs of protons and measure how often they fly off in the same direction, you can work out the size of that cloud. This method is called femtoscopy: it works like a microscope for nuclear scales.

A laser hits a target of thin wires, and within tens of femtoseconds (billionths of a billionth of a second) knocks out a stream of protons. These protons fly into a converter made of lithium and deuterium, where neutrons are born.

Fusion, the merging of a proton with a boron-11 nucleus, promises a near-perfect energy source: no dangerous neutron flux, just a stream of charged particles that can be directly converted into electric current. But there's a fundamental problem: the Coulomb barrier.

Inside every atom lives a proton. For a long time, it was considered as eternal as matter itself. But theories that unify all forces of nature predict that, sooner or later, the proton will decay. The only question is how long we have to wait. In the Japanese detector Super-Kamiokande — a giant tank of ultra-pure water — physicists searched for signs of such a decay.

In the binary system Cygnus X-3, right here in our Galaxy, a black hole and a giant star whirl so tightly together that the star loses matter: it's swept away by a powerful wind. Jets blast out from near the black hole; recently, a telescope caught photons from them, each carrying the energy of a flying mosquito.

Neutrinos are tiny particles that zip through Earth, barely noticing it. In the MicroBooNE experiment, they are caught in a tank of liquid argon. When a neutrino strikes an argon nucleus, it produces an electron and protons, like splashes from a stone thrown into water.

The proton is not a solid ball. Its charge, mass, and other properties are distributed differently in space, and each property has its own radius. Physicists have long been able to measure where the proton's charge is concentrated and where its mass lies.

When a fast proton slams into an atomic nucleus, new particles are born for an instant. One of them is the phi meson: a short-lived clump of matter that decays into an electron-positron pair. Catching this decay is like hearing the echo of a distant explosion: the blast itself is over, but its trace is still flying.

Every time deuterium and tritium fuse in a fusion reactor, a fast neutron flies out. It can turn one substance into another — for example, create valuable isotopes for medicine. Today such neutrons cost a fortune, because there are few experimental facilities and they rarely operate.

In collisions of heavy nuclei, a fireball of thousands of particles is born. Among them are pions and kaons, two kinds of light particles that look very much alike. To understand what happens in this fireball, physicists need to know exactly how many of each particle flew out.

The Large Hadron Collider doesn't just smash protons: it also collides entire atomic nuclei. When two nuclei smash together at tremendous speed, they create a tiny blob of matter so hot that protons and neutrons melt into a 'soup' of quarks and gluons.

In the 2010s, physicists working at the Large Hadron Collider learned to create in the lab a substance that doesn't exist in the ordinary world.

The atomic nucleus is not a solid ball but a drop of liquid that can be squeezed. To understand how elastic it is, physicists accelerate gold nuclei and smash them into each other. On impact, the matter compresses to densities like those in a neutron star, then flies apart. The shape of this debris tells us about the properties of the matter inside.

At the Large Hadron Collider, physicists accelerate protons to nearly the speed of light and smash them together. Usually, the protons themselves take part in such collisions, but sometimes they pass close by without touching, and it is their electric fields that interact.

In the first moments after the Big Bang, space boiled. A superheated substance permeating the world gave rise to giant bubbles of a new phase – much like a liquid produces vapor. Collisions of these bubbles accelerated particles to energies unimaginable in Earthly accelerators.

Imagine a bridge with its middle ripped out: cars on the other side would be a surprise. That's how astronomers long viewed black holes with masses from 50 to 130 solar masses: the stars that could produce them explode as pair-instability supernovae.

A snowflake falling from a cloud chooses between a left-handed and a right-handed form. The difference between them is almost imperceptible, like a breath of wind, yet it is that very breath that decides which pattern will grow.