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Category: cosmology

After nearly 100 years, scientists may have detected dark matter

In the early 1930s, Swiss astronomer Fritz Zwicky observed galaxies in space moving faster than their mass should allow, prompting him to infer the presence of some invisible scaffolding—dark matter—holding the galaxies together. Nearly 100 years later, NASA’s Fermi Gamma-ray Space Telescope may have provided direct evidence of dark matter, allowing the invisible matter to be “seen” for the very first time.

Dark matter has remained largely a mystery since it was proposed so many years ago. Up to this point, scientists have only been able to indirectly observe dark matter through its effects on observable matter, such as its ability to generate enough gravitational force to hold galaxies together.

The reason dark matter can’t be observed directly is that the particles that make up dark matter don’t interact with electromagnetic force—meaning dark matter doesn’t absorb, reflect or emit light.

Recently discovered X-ray transient traced to possible collapsar origin

Using various ground-based and space telescopes, an international team of astronomers has observed a recently discovered fast X-ray transient designated EP 241021a. Results of the multiwavelength observational campaign, published November 17 on the pre-print server arXiv, shed more light on the behavior and nature of this transient.

Fast X-ray transients (FXTs) are bursts in soft X-rays lasting from a few hundred seconds to several hours. They are very difficult to detect because they occur at unpredictable locations and times and their activity is very brief. Moreover, their nature is still puzzling. However, astronomers trying to explain their origin take into account several scenarios; for instance, stellar flares, supernova shock breakouts, and long gamma-ray bursts (GRBs).

EP 241021a is an FXT detected on October 21, 2024, with the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe (EP) satellite, at a redshift of 0.75. It exhibited a luminous soft X-ray flash lasting about 100 seconds and a peak 0.5–4 keV luminosity of approximately one quindecillion erg/s.

Yes, the Universe Can Expand Faster Than Light

An expanding universe complicates this picture just a little bit, because the universe absolutely refuses to be straightforward. Objects are still emitting light, and that light takes time to travel from them over to here, but in that intervening time the universe grows larger, with the average distance between galaxies getting bigger (yes, I know that sometimes galaxies can collide, but we’re talking on average, at big scales here).

So when we see an image of a distant galaxy, and that light has traveled for billions of years to finally end in our telescopes, we don’t know how far away that galaxy is right now, at the moment that we get the light. We have to turn to a cosmological model that incorporates the expansion history of the universe, so we know how much the universe has grown in a given amount of time.

Our current best model of the universe is called LCDM, which involved both dark matter (different episode) and dark energy (different episode). We can discuss the relative merits and weaknesses of LCDM (different episode), but for now let’s just take it as a given, as deviations from LCDM don’t really change the picture much.

The Universe Could ‘End’ With a Dark Eternity, an Astrophysicist Explains

Whether the Universe will ‘end’ at all is not certain, but all evidence suggests it will continue being humanity’s cosmic home for a very, very long time.

The Universe – all of space and time, and all matter and energy – began about 14 billion years ago in a rapid expansion called the Big Bang, but since then it has been in a state of continuous change.

First, it was full of a diffuse gas of particles that now make up atoms: protons, neutrons, and electrons. Then, that gas collapsed into stars and galaxies.

What is Time? Stephen Wolfram’s Groundbreaking New Theory

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What is time? Is it just a ticking clock, or is it something more profound?

In this thought-provoking episode of Into the Impossible, Stephen Wolfram challenges everything we know about time, offering a revolutionary computational perspective that could forever change how we understand the universe.

Stephen Wolfram is a computer scientist, physicist, and businessman. He is the founder and CEO of Wolfram Research and the creator of Mathematica, Wolfram Alpha, and Wolfram Language. Over the course of 4 decades, he has pioneered the development & application of computational thinking. He has been responsible for many discoveries, inventions & innovations in science, technology, and business.

He argues that time is the inevitable progress of computation in the universe, where simple rules can lead to complex behaviors. This concept, termed computational irreducibility, implies that time has a rigid structure and that our perception of it is limited by our computational capabilities. Wolfram also explores the relationship between time, space, and gravity, suggesting that dark matter might be a feature of the structure of space.

Tune in to discover the true nature of time.

Continue reading “What is Time? Stephen Wolfram’s Groundbreaking New Theory” | >

Endings and beginnings: Atacama Cosmology Telescope releases its final data, shaping the future of cosmology

There’s always a touch of melancholy when a chapter that has absorbed years of work comes to an end. In the case of the Atacama Cosmology Telescope (ACT), those years amount to nearly 20—and now the telescope has completed its mission. Yet some endings are also important beginnings, opening new paths for the entire scientific community.

The three papers published in the Journal of Cosmology and Astroparticle Physics by the ACT Collaboration describe and contextualize in detail the sixth and final major ACT data release—perhaps the most important one—marking significant advances in our understanding of the universe’s evolution and its current state.

ACT’s data clarify several key points: the measurement of the Hubble constant (the number that indicates the current rate of cosmic expansion—the universe’s “speedometer”) obtained from observations at very large cosmological distances is confirmed, and it remains markedly different from the value derived from the nearby universe. This is both a problem and a remarkable discovery: it confirms the so-called “Hubble tension,” which challenges the model we use to describe the cosmos.

A 13-Billion-Year-Old Signal Could Finally Reveal the First Stars

Astronomers are uncovering new ways to study the universe’s first stars, objects too distant and faint to observe directly, by examining the ancient 21-centimeter radio signal left behind by hydrogen atoms shortly after the Big Bang. Understanding how the universe shifted from complete darkness t

Artificial spacetimes for reactive control of resource-limited robots

Not metaphorically—literally. The light intensity field becomes an artificial “gravity,” and the robot’s trajectory becomes a null geodesic, the same path light takes in warped spacetime.

By calculating the robot’s “energy” and “angular momentum” (just like planetary orbits), they mathematically prove: robots starting within 90 degrees of a target will converge exponentially, every time. No simulations or wishful thinking—it’s a theorem.

They use the Schwarz-Christoffel transformation (a tool from black hole physics) to “unfold” a maze onto a flat rectangle, program a simple path, then “fold” it back. The result: a single, static light pattern that both guides robots and acts as invisible walls they can’t cross.

npj Robot ics — Artificial spacetimes for reactive control of resource-limited robots. npj Robot 3, 39 (2025). https://doi.org/10.1038/s44182-025-00058-9

When superfluids collide, physicists find a mix of old and new behavior

Physics is often about recognizing patterns, sometimes repeated across vastly different scales. For instance, moons orbit planets in the same way planets orbit stars, which in turn orbit the center of a galaxy.

When researchers first studied the structure of atoms, they were tempted to extend this pattern down to smaller scales and describe electrons as orbiting the nuclei of atoms. This is true to an extent, but the quirks of quantum physics mean that the pattern breaks in significant ways. An electron remains in a defined orbital area around the nucleus, but unlike a classical orbit, an electron will be found at a random location in the area instead of proceeding along a precisely predictable path.

That electron orbits bear any similarity to the orbits of moons or planets is because all of these orbital systems feature attractive forces that pull the objects together. But a discrepancy arises for electrons because of their .

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