cosmology

A census by body shape: that's one way to describe what astronomers did with 6348 massive galaxies. Instead of height and weight, they measured how concentrated the light is toward the center, how flattened the galaxy is, and how asymmetric its shape is. Then they ran the same measurements on galaxies from three computer models of the universe and compared the results.

A river drawn on a map is always a single line. But stand on the bank, and you will see that within the channel there are faster currents, eddies, and branches that merge and split. The cosmic web is like that river, but made of dark matter, and until recently astronomers drew it as a single line.

In the heart of an old city stands a clock tower whose hands have never been adjusted since it was built. By how far it runs slow, you can calculate how much time has stretched since then. In space, the role of such towers is played by relic galaxies — dense stellar systems that formed in the first few billion years and have since neither merged with neighbors nor given birth to new stars.

A sunspot, a dark island on the fiery surface, lives its own turbulent life. Beneath it, in invisible depths, giant magnetic loops drift like twisted cables. When such a loop emerges, it can discharge as a flare, and hurl clouds of charged particles into space. Scientists have long tried to understand what determines the strength and suddenness of these events.

The night sky looks like a random scattering of stars. But zoom out to enormous distances, and the chaos disappears. Galaxies gather into long filaments and flat walls, with colossal voids gaping between them — cosmic voids. This structure is called the cosmic web.

The standard cosmological model ΛCDM (which includes dark energy and cold dark matter) is the score of a cosmic symphony. It describes how space expanded after the big bang. How dark matter clumped together. How galaxies ignited. For a long time, everything played flawlessly.

The early Universe was not just a hot soup of particles. In the first fractions of a second, mirror symmetry could have been broken: the world and its reflection would not be quite identical. If so, the large-scale cosmic web of galaxies would retain a barely noticeable 'curl'—as if all matter were slightly twisted in one direction.

The early universe was less like a calm pond and more like a boiling cauldron. Matter flowed, collided, and swirled against the backdrop of rapid spatial expansion. To understand how stars and galaxies emerged from this hot soup, physicists build digital simulations. This new work is the third part in a series on lattice-based cosmological modeling. The first two focused on fields; this one deals with fluids.

Right after the Big Bang, space cooled unevenly. In some places, folds could have formed — threads of energy as thin as a hair but incredibly dense. Physicists call them cosmic strings. They oscillate, collide, and emit gravitational waves — ripples in the fabric of space itself.

380 thousand years after the Big Bang, the universe cooled enough for light to decouple from plasma. That cosmic microwave background still pervades space, like the first chord of a symphony, the echo of a fiery beginning.

Three invisible strings oscillate in the intergalactic void. This is not poetry, but a hypothesis about the nature of dark matter — an ultralight quantum field with spin 1, carrying three polarizations.

2.1 × 10⁻⁹ — that's the temperature variation across the sky, about the same as measuring ripples a fraction of a millimeter high on the ocean surface. This microscopic non-uniformity is imprinted in the cosmic microwave background and tells the story of the very beginning of time.

The first three minutes after the birth of the world are a cosmic kitchen where nature cooked the lightest atomic nuclei. The recipe is set by gravity: it controls the cooling rate of the hot 'broth' of particles. If gravity worked differently than we are used to, the dish would have turned out different — with different amounts of helium and deuterium.

Deep in the Amazon rainforest, beneath a multi-layered canopy of leaves, lie vast earthen figures — squares, rectangles, the occasional rhombus. For decades they teased archaeologists with their silent geometry, until a researcher armed with orbital optics saw them as an astronomical instrument.

The mystery of antimatter in space has long puzzled astrophysicists: where do positrons come from, settling like snowflakes into our detectors? The answer might lurk in the most ubiquitous gamma-ray background. The Universe is soaked in diffuse light — the cosmic photon background (CPB).

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…

The standard cosmological model ΛCDM, where dark matter and dark energy act as the chief architects of the cosmos, has predicted astronomical data with Swiss-watch precision for decades. Its foundation was laid by three geniuses.

When we peer deep into space, we see the past. Edwin Hubble’s law turns redshift into a time machine: light from galaxy UDS 12999 traveled to us for 7.6 billion years — more than half the age of the Universe.

The cosmological principle – the notion that the Universe is homogeneous and isotropic on large scales – has guarded our understanding of the world since the time of Edwin Hubble and Georges Lemaître, whose ideas formed the basis of the Big Bang model.

The universe hasn't always been expanding. In some models, it first contracted, nearly empty and flat, and then, upon reaching a limit, bounced back and started growing, like the world we know. This scenario is called bouncing cosmology.

From childhood, we're used to thinking of space as infinite and isotropic. But Einstein and Lemaître were already asking: could the Universe be closed in on itself, like a Möbius strip or a 3-torus?

Lenticular galaxies are the cosmic quiet types: they have a disk but no bright spiral arms. For a long time, their origin remained a mystery. A team of scientists ran the Hydrangea computer simulation and traced the fate of each galaxy from its youth to the present day. On the mass–size diagram, these galaxies line up in a V shape.

In the first instants after birth, the universe might have been multidimensional, like a sheet of paper that suddenly gained thickness. This "thickness"—the extra dimensions — began to inflate rapidly. Such superfast growth is called inflation.

Since the end of the 20th century, we've known: the expansion of the Universe is accelerating — galaxies are flying apart faster and faster. The discovery brought a Nobel Prize to Adam Riess, Saul Perlmutter, and Brian Schmidt.

The Universe resembles a dense forest: up close, individual galaxy-trees are visible, gathered into groves, but from a distance everything merges into a solid green canopy. The boundary beyond which the cosmos becomes homogeneous is called the angular scale of homogeneity: it's the size of a patch of sky from which galaxies are distributed evenly.

Our universe isn't just expanding: it's doing so faster and faster. It's like raisin bread dough in the oven: the raisins move apart, and the farther they've already separated, the faster they continue to recede. The strange force pushing the cosmos apart is called dark energy. Most scientists think it's constant, like a permanent spring built into the very fabric of space.

A blacksmith forges a sword. With each hammer blow, the red-hot metal flattens, but the hammer, the anvil, and the surrounding air all warm up slightly. Part of the impact energy is irreversibly lost as heat — a trade-off familiar to anyone who has ever driven a nail, and it turns out to be the key to the biggest mysteries of the cosmos.

Ancient light, traveling 14 billion years, reaches us from all directions. At first glance, it looks perfectly smooth, but if you look closely, tiny fluctuations appear, like ripples on a still pond. Those ripples aren't random noise; they're an encoded history of the universe.

A magnet with only one pole — north, but no south. Split it in half, and instead of two ordinary magnets, you get two more one-pole magnets. In our world, no such particle has been found, although many theories predict their existence. These hypothetical objects are called magnetic monopoles. The authors of the study noticed a curious connection.

Cosmology is going through strange times. On one hand, the standard model with dark matter and dark energy beautifully describes the large-scale structure. On the other, it's cracking at the seams.

The classic story of the Universe’s birth from a blazing point called the Big Bang raises uncomfortable questions: why is the cosmos so homogeneous, and what was before the singularity?

Physics often resembles the construction of a giant ship — the Universe. The physicist-engineers have yet to agree on the basic blueprints.

A pendulum chooses how to swing on its own. If you give it a strong push, it quickly returns to a smooth rhythm. If you hold it at its extreme position, it will stay there, but as soon as you let go, it resumes its usual motion.

Imagine inflating a balloon. It expands quickly at first, then slows down, and then suddenly speeds up again, as if someone gave the pump another squeeze. That's what seems to be happening to our universe.

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.

The Universe is like an inflating balloon. Quantum mechanics forbids measuring exactly how big it is and how fast it's inflating at the same time. This principle permeates the cosmos: a new equation states that the Universe's expansion and its size are linked by a fundamental uncertainty.

Edwin Hubble and Georges Lemaître discovered the expansion of the Universe nearly a century ago. One way to test it is the surface brightness test: in an expanding cosmos, the light of a distant galaxy should fade like a pattern on a stretching film.

In the scorching solar corona, where temperatures soar past a million degrees, float cold, dense clouds — solar prominences. They hang for weeks, neither falling nor dissolving, like icebergs in a boiling ocean. How they got there is a question that has puzzled astronomers for decades.

Globular clusters are dense 'balls' of hundreds of thousands of stars that orbit the center of the Milky Way. Some were born in our Galaxy, others were captured when the Milky Way swallowed dwarf satellite galaxies. They can be distinguished by chemical composition, but astronomers now have a new tool — dynamical age.

You are pacing a huge hall in complete darkness. You walk from wall to wall, counting your steps, and suddenly realize that the distances don't add up as they should. It seems as if the floor is not flat but bulging like a hump or hollowed like a bowl. That's roughly what astronomers found when studying distant galaxies and sound waves frozen in the early Universe.