information loss

A boiling kettle on the stove eventually boils dry — and so, according to the classical picture, a black hole should gradually vanish in a hiss of radiation. But what if you add a special ingredient to the kettle?

Alice prepares a quantum particle in one of several states and sends it to Bob. The channel the particle travels through isn't perfect: it's noisy, scatters, interacts with the environment. Bob receives the signal and tries to figure out what Alice actually sent. This is the classic "prepare-send-measure" scheme, and there's always a risk of losing something along the way.

A black hole has three laws, just like an ideal gas. The first: energy is conserved. The second: the horizon area never decreases. And the third, the most finicky, demands that at zero temperature the entropy (a measure of disorder) tend to zero or a universal constant.

A fussy thermometer shows different temperatures depending on who is looking at it. A black hole behaves much the same way: its thermal properties, entropy and temperature, depend on how we describe the information hidden inside.

A star circles a rotating black hole like a figure skater at the center of a rink. While it is far away and can be treated as a point, the dance remains predictable: the orbit follows clear laws, like music that is easy to glide to. But as it approaches, gravity begins to act unevenly.

General relativity, which describes the structure of the universe, does not forbid closed timelike curves. But Stephen Hawking put forward the 'chronology protection' conjecture: quantum effects should destroy such curves, making time travel to the past impossible.

Water turns to ice at zero degrees — sharply, with no intermediate states. Something similar happens to complexity when we take a random quantum state of an entire system and look only at a part of it. As long as that part occupies less than half the system, its complexity grows smoothly. But as soon as the fraction crosses 50%, a jump occurs.

A black hole is not eternal. Even in a perfect vacuum, it slowly loses energy — a process known as Hawking radiation. Quantum effects near the event horizon create pairs of particles, one of which escapes, carrying away some of the black hole's mass.

The universe cooled like a giant bathtub after a hot start. At 400 000 years after the Big Bang, hydrogen was ready to recombine — protons capturing electrons to become neutral atoms. But somewhere in this dark water, a tap kept dripping.

The agony of a solitary black hole lasts forever. But in its final moments, as its mass evaporates according to the law discovered by Hawking, it manages to send a radio farewell signal. Not a quantum whisper, but a classical hum — if only there's a magnetic field nearby.

The cosmological horizon — the edge of the observable Universe, which is expanding at an accelerating rate — is like a safe with a timer. Information about what crosses this boundary doesn’t vanish but returns, albeit with a delay. Physicists have figured out how long this pause lasts.

The merger of two black holes is not just a silent dance, but a grand act after which spacetime itself vibrates for a long time. These damped oscillations — quasi-normal modes — are like the ringing of a gigantic bell. But there is another echo: barely perceptible, almost ghostly.

A black hole is like a perfectly dark room: from outside, you can't see what's inside, and anyone crossing the threshold seems to vanish from the outside world. But what does the falling observer feel? In classical physics, nothing special: the event horizon isn't marked by any signpost.

Traditionally a black hole was described by three parameters — mass, charge, and angular momentum.

A black hole resembles a safe that slowly gives up its contents, energy and information, through a faint glow known as Hawking radiation. But if the safe opens too quickly, a 'firewall' may flare up at its boundary — a region where the familiar laws of physics break down. In the new work, physicists complicated the model of this safe.

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.

A black hole is like a perfect vacuum cleaner: anything that crosses its horizon vanishes without a trace. But this vacuum cleaner has a strange feature: its "dust bag" grows, and by the size of the bag you can tell how much has been sucked in. In black hole physics, this size is linked to entropy entropy — a measure of hidden information about what fell inside.

A star contracts under its own gravity, and at some point its fate hangs on a razor-thin balance. Classical physics paints a grim picture: if the mass and the force of compression are tuned with terrifying precision, what emerges is not a black hole but a 'naked' singularity.

Erasing even a single bit means releasing heat. This discovery by Rolf Landauer hinted that information is neither material nor illusory. Imagine that every event casts a shadow: that is information, the collection of all unrealized possibilities.

A bonfire doesn't burn out all at once. If you glance at the flames at a random moment, all you see is a jumble of fire tongues, and you can never tell what exactly burned: a wet branch, an old magazine, or an armful of dry grass. But if you watch the fire hour after hour, rhythms emerge in its dance: a burst of heat, a lull, a change in color. These rhythms tell the story of what was thrown into the flames.

A swarm of tiny ice balls is scattered across a warm room. Some melt faster, others slower, but when only wet spots remain, they all vanish in the same way: the last drop evaporates according to the same law. This is roughly how primordial black holes behave — hypothetical objects born in the first moments after the big bang.

A black hole is not an eternal vacuum cleaner. Left alone in the void, it slowly disappears, radiating energy like a puddle drying on asphalt. This process, predicted by Stephen Hawking, is called evaporation.

A black hole is like a pot that slowly boils away. Its surface emits particles, a process known as Hawking radiation. The hotter the pot, the faster it empties. But what if the pot is not ordinary, but has a double bottom — capable of turning into a passage to another place?

Black holes lose mass like water from a bucket in the sun — an evaporation discovered by Stephen Hawking.

A light beam approaches a black hole not head-on, but at a glancing angle. If the angle is just right, the light neither falls in nor escapes: it starts looping around, like a figure skater circling the rim of a funnel. This narrow track is the photon ring. It acts like a lens, repeatedly reflecting the image of everything that falls into the hole.

A black hole is like a perfect safe: anything that goes in seems lost forever. But at the microscopic level, it doesn't destroy information: it shuffles it with its internal degrees of freedom, much like a deck of cards after a thorough shuffle.

A black hole is like an ember that was thought to smolder forever, but eventually must go out — evaporating without a trace.

In the early Universe, primordial black holes emerged — objects no larger than an atom but with the mass of a mountain. They gradually evaporate and, before disappearing, should produce gravitational waves — ripples in spacetime. If they were all identical, they would pop simultaneously, like popcorn kernels: the roar would be deafening.

A sugar cube weighs about a gram. But a black hole that could hide inside such a cube would weigh as much as a small mountain — billions of tons. Yet even such tiny things, born in the first instants after the Big Bang, should have vanished long ago.

A quantum particle can be in two states at once, like a coin spinning, both heads and tails. Near a black hole, the event horizon, where spacetime curvature bends space and time to the extreme, acts as a one-way gate.

When a balloon with a painted pattern deflates, the pattern ripples and distorts. Something similar happens to a black hole that slowly evaporates, losing energy through the radiation discovered by Stephen Hawking.

Twenty-first-century astrophysics is deafening with triumphs: we’ve caught the tremor of spacetime from the merger of invisible giants; glimpsed the 'shadow' of a supermassive monster in a distant galaxy; traced the orbits of stars dancing around a compact something at the heart of the Milky Way.

If you shrank an ordinary black hole to the size of a grain of sand, it would shine like a tiny star and quickly vanish in a flash. That's Stephen Hawking's prediction: the event horizon acts like a hot surface emitting particles.

In 1965, Penrose unleashed a mathematical thunderbolt on physics: any sufficiently massive star, shrinking under its own weight, inevitably collapses into a singularity — a region where spacetime curvature becomes infinite and the laws of physics break down.

Black holes are not eternal: they slowly lose energy, emitting entropy — a measure of hidden information — as heat. This process was predicted by Stephen Hawking. But until now, it remained a mystery what happens at the very end, when the hole has almost disappeared and must return the captured data.

Water boils in a pot, and bubbles rise from the bottom. They grow, float up, and pop, and the water remains water. Something similar, physicists have found, can happen to space itself — if it contains dark energy (the mysterious force accelerating the expansion of the universe). In such an eternally inflating universe, black holes are sometimes born.

A star that has exhausted its fuel falls into itself. Its outer layers fly apart, while the core compresses to unimaginable densities. It was once thought that this process ends in a point — a singularity where the laws of physics break down. New work shows that just before the very end, something strange happens inside the future black hole.

A tiny black hole — the size of an atom but as massive as a mountain. It wasn't born from a star but in the first instants after the big bang, and it has been quietly losing mass ever since, radiating heat.

The standard picture of black hole evaporation, painted by Hawking, long seemed reassuring: quantum fluctuations near the horizon produce thermal radiation, the hole slowly melts away, and the spacetime behind it remains smooth.

A stone falls into a pond, and the ripples on the water tell for a long time where it sank. With a black hole, it would seem, things are different: everything that crosses the horizon (the boundary from beneath which not even light can escape) vanishes without a trace.