locality

In nature's workshop, there is a strange lathe: it cuts threads on screws but forbids left-handed ones. You can tighten a screw as much as you like, in any clockwise direction, but counterclockwise is not allowed. This lathe is not a fantasy but an exact quantum rule that physicists have just built for magnetic materials.

Two tiny diamonds float in a vacuum, separated by a distance that light cannot cross during the experiment. Inside each, like a frozen spark, resides an entangled spin — a quantum state linking them into a single whole. Now the diamonds begin to move, but not just any motion: each one seems to split, existing in two places at once.

In the quantum world, a fact becomes objective when its value is imprinted on many independent fragments of the environment, like a notice posted on hundreds of bulletin boards across the city. Each copy alone adds no new information, but it changes the rules of the game for anyone trying to erase that information.

Electric charge is a slippery thing. You can measure how much there is in the entire universe or in a single particle, but try to point your finger and say, 'Right here, in this cubic centimeter, there is exactly this much charge right now,' and you hit a fundamental wall. The issue is that total charge, which physicists denote by the letter Q, is nonlocal.

Gravity in our world is curved spacetime. That's how Einstein's general theory of relativity describes it. But what happens to gravity at the level of atoms and particles, where quantum mechanics rules? This question has remained unanswered for nearly a century.

Building a house on sand is a bad idea. In physics, it was long believed that a quantum theory of gravity could not be built on a fixed "sand"—a pre-existing spacetime.

Light or sound can be confined in a tiny region of a crystal, like a pearl in a shell. Usually, two methods are used. The first is like a heavy ball in a pit: a particle with large mass simply cannot roll out. The second is a perfect cage of mirrors, where waves cancel each other everywhere except in the trap itself.

At the very beginning of the universe, when all of space was compressed into a point, the laws of physics break down. This point is called a singularity — an edge where our equations lose meaning. But what if it's not an end, but a special type of boundary? The authors of this work propose viewing the singularity as a free boundary.

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.

Light cones are not about light; they are boundaries in spacetime that separate causes from effects. These cones are not rigid: a massive object curves them, like a heavy ball pressing into a stretched sheet.

Three people sit in three corners of a room. Each receives a sealed envelope from an invisible courier, but the couriers do not coordinate and have never met. The people open the envelopes and see a note with one word: "yes" or "no." They choose nothing themselves: they just read.

When two black holes merge, their event horizons – surfaces of 'no return' – combine like two pieces of sticky film. The total area never decreases. This is the law discovered by Stephen Hawking in the 1970s.

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.

Two coins are flipped in different cities, but they always land the same way. Physicists call this entanglement: particles behave as if an invisible thread connects them. But what if the thread isn't instantaneous, just very fast — still not faster than light? Then some signal could slip between measurements, and the coincidences would be explained without any magic.

Toss a handful of pebbles into a stream: some settle on the bottom, others get swept around. That's roughly how waves behave in a disordered medium — light in frosted glass, sound in porous material. Usually, disorder slows things down: the wave gets stuck, spreads out, loses direction. But in a new study, physicists built an acoustic lattice where things work differently.

According to the laws of physics, nothing can outrun light, otherwise for some observers the effect would occur before the cause. Artur Ekert and Andrzej Dragan showed that this situation creates an uncertainty resembling quantum indeterminacy.

Spacetime at ultra-short distances resembles a digital screen: it's not smooth but made of tiny 'pixels.' This minimum length was calculated by Max Planck, and Heisenberg's uncertainty principle explains why the world cannot be continuous: precise measurement always…

In the quantum world, an object can be in several places at once. Yet in everyday life we see things strictly in their places. The reason is gravity. A massive star under its own weight inevitably collapses into a black hole or a neutron star, but it can't be both at the same time.

According to physicist Hugh Everett, every observation splits the universe into parallel branches. Normally, your memory of the outcome locks you into one branch, like a key keeping a door shut. A new protocol, reality steering, shows you can pick that lock: erase the memory, and the barrier fades, letting you slide into another reality.

A quantum computer is like an exquisite dish. There are recipes for ordinary kitchens, but special quantum states are secret ingredients that turn the dish into a masterpiece. One of them is 'magic'. The term was coined by John Preskill in 2018.

Two massive spheres in the cosmic void. Push one, and the second will feel the push only after a moment: gravitational influence travels, like an echo of a shout in the mountains, with inevitable delay. This is how curved space transmits signals locally, step by step — predicted by Einstein long ago.

The Social Laser theory describes society by borrowing the inner workings of a laser. People, like atoms in a crystal, absorb streams of information and become charged by it. When the number of those charged with a single idea outweighs the indifferent, even a weak signal (a post, a call to action) makes everyone act as one.

Two couriers leave the same city in opposite directions. An hour later, each opens an envelope: one contains a slip marked “plus,” the other “minus.” How did they know who would get which?