All posts tagged: dark energy

Supernovae help astronomers measure how the Universe expands over time

Supernovae help astronomers measure how the Universe expands over time

Published by Jenni Sidey

Astronomers have leaned on Type Ia supernovae for decades because these stellar explosions act like mile markers across the cosmos. You simply measure how bright one appears, and then compare that with how bright it ought to be. After that, you can estimate how far away it is. Additionally, when you stack enough of those measurements together, a picture of how the Universe has expanded over time begins to emerge. That picture, though, is never as clean as it sounds. The light from a supernova reaches Earth carrying more than one message at once. Part of it reflects the explosion itself. Part of it is shaped by the star that blew apart, including its age and chemical makeup. Another part has been dimmed or reddened by dust in and around the galaxy where the blast happened. And part of it has been stretched by the expansion of the Universe. A new analysis from Konstantin Karchev and Roberto Trotta of SISSA, working with Raúl Jiménez of the University of Barcelona, tries to sort out those overlapping …

Microscopic wormholes may be warping reality all around us

Microscopic wormholes may be warping reality all around us

Published by Jenni Sidey

For decades, cosmologists have had an awkward number sitting at the center of their equations. The universe is expanding, and that expansion began speeding up in the recent cosmological past. The usual way to describe that behavior is with a positive cosmological constant, often written as Λ. But when physicists try to calculate that value using quantum field theory, the answer comes out wildly wrong, up to 120 orders of magnitude larger than what astronomers actually observe. That mismatch is one of the biggest unresolved problems in modern physics. A new paper in Physical Review D does not claim to solve it outright. But researchers from the University of Thessaly in Greece argue that a strange ingredient from quantum gravity, microscopic wormholes flickering through spacetime foam, could generate an effective cosmological constant of the right kind, and possibly behave like a dark energy sector as well. Wormholes do not act as dark energy in a simple, direct sense. (CREDIT: iStock images) Where the mismatch begins The paper starts from a familiar tension in cosmology. One …

The rise, the fall and the rebound of cyclic cosmology

The rise, the fall and the rebound of cyclic cosmology

Published by skeptic

The largest 3D map of our universe to date, with Earth at the center and every dot showing a galaxy DESI collaboration and KPNO/NOIRLab/NSF/AURA/R. Proctor The universe is dead; long live the universe. Not right at this moment, not yet. But one day everything we know will be gone. The cities we build, the lakes we swim in, the planet we live on, the solar system we inhabit, the star we orbit and every star we don’t – they’re all headed towards an inescapable finale. At the end of it all, what happens? Some say our ever-expanding universe will slow down and then one day do a cosmic U-turn, undoing all the growth that has happened since the big bang. Eventually, everything will crunch together into the tiniest possible space and then explode out again in a riot of rebirth – that’s the idea we call cyclic cosmology, or the big bounce. It’s been around for a long time, and the idea itself has faced a trajectory that mirrors its contents. It was briefly popular …

Scientists reveal the hidden forces shaping how gravity works across the Universe

Scientists reveal the hidden forces shaping how gravity works across the Universe

Published by Jenni Sidey

Gravity behaves predictably in your daily life. Drop a ball, and it falls. Planets loop around stars. On paper, the same rules should also govern matter spread across the universe. But the farther astronomers look, the more that certainty gets tested. That question sits at the center of a new analysis of galaxy motions on enormous cosmic scales. The work used light from the cosmic microwave background, combined with a large galaxy survey, to ask something deceptively simple: does gravity still follow the familiar inverse-square law across vast stretches of space? For now, the standard picture appears to be holding up. Researchers like Patricio A. Gallardo from the University of Pennsylvania tested how galaxy groups and clusters move toward one another over distances of tens of millions of light-years. Their results lined up well with the expectations of the standard cosmological model, known as Lambda-CDM, which combines general relativity, dark matter, and dark energy. A competing idea, modified Newtonian dynamics, or MOND, did not match the data nearly as well. Patricio Gallardo and his collaborators used …

Our local universe’s expansion rate doesn’t add up, astronomers find

Our local universe’s expansion rate doesn’t add up, astronomers find

Published by Jenni Sidey

A difference of a few kilometers per second might not sound like much. In cosmology, it has become one of the field’s most stubborn problems. An international team of astronomers has now delivered one of the sharpest direct measurements yet of how fast the nearby Universe is expanding, and the answer again lands on the high side. Their new value for the Hubble constant, the number used to describe that expansion rate, is 73.50 ± 0.81 kilometers per second per megaparsec. That is just over 1% precision. It also keeps the long-running Hubble tension very much alive. The result, published in Astronomy & Astrophysics, comes from the H0 Distance Network Collaboration, or H0DN. The project grew out of a March 2025 workshop at the International Space Science Institute in Bern, Switzerland, where researchers from across the field worked to build a shared framework for combining local measurements of cosmic distance. This graphic represents the tension that exists between measurements of the expansion rate of the late, nearby Universe, versus what would be expected based on …

The bombshell results that demand a new theory of the universe

The bombshell results that demand a new theory of the universe

Published by skeptic

If you imagine the story of the universe as a film endlessly in post-production, cosmologists would be its obsessive editors, constantly tweaking the narrative. The version they are working with is an astonishing cinematic achievement: it starts with a bang, space-time erupting out of nothing, before unfurling majestically with the formation of stars and then galaxies, sculpted by the gravitational pull of both visible matter and mysterious dark matter, all the while serenely expanding thanks to a shadowy force known as dark energy. But it can’t be the final cut. The more we peer into space, the more it seems incomplete: the story contains niggling inconsistencies and key protagonists remain maddeningly elusive. For decades, cosmologists have been struggling to refine the script. Now, they finally have fresh inspiration from the cosmos. A powerful telescope has mapped millions of distant galaxies to trace the expansion of the universe with unprecedented precision. What it appears to be revealing is that dark energy behaves so weirdly, it can’t be what we thought it was. If confirmed, it is …

A bizarre type of black hole could solve three cosmic mysteries in one

A bizarre type of black hole could solve three cosmic mysteries in one

Published by skeptic

Deborah Ferguson (UT Austin), Bhavesh Khamesra (Georgia Tech), and Karan Jani (Vanderbilt University)/LIGO Space-time is being driven apart. Every second that passes, the universe expands faster and faster. What is propelling this dramatic acceleration is an enigma, though – one scientists have known about, and searched for, for decades. Still, we are no closer to understanding it. We call it dark energy, but we know next to nothing about what it is or where it comes from. Nevertheless, it makes up about 68 per cent of the universe. It would be reasonable, however, to assume this mystery has nothing to do with black holes: behemoths so gravitationally powerful that once something is drawn in past a certain point, it can never escape. They pull matter towards them, so how could they be driving the universe’s expansion? Yet that’s exactly what a small group of astrophysicists is suggesting. The story goes like this: all matter that falls into black holes goes through a process that turns it into a kind of radiation. This, in turn, exerts a force on the space around it. Such an effect would be too small to notice in the immediate surroundings, but add together all the black holes …

Dark Energy Survey delivers its most precise cosmic map yet

Dark Energy Survey delivers its most precise cosmic map yet

Published by Jenni Sidey

Dark energy remains one of the most stubborn puzzles in modern science. Despite decades of observation and increasingly powerful telescopes, its true nature is still unknown. Now, scientists involved in the Dark Energy Survey, a six-year international project led by researchers from institutions including Northeastern University and supported by U.S. and global partners, have released their final results. The findings do not deliver a breakthrough explanation, but they narrow the field and sharpen the questions guiding future research. Jonathan Blazek, Northeastern University physics assistant professor and co-lead of the survey’s modeling and analysis team, indicates there is advancement made through precision. “While we’ve offered some hints as to what dark energy may be, we’ve yet to answer all of these questions,” said Jonathan Blazek. “What we do know is, better than ever before, what questions we should pursue and how to approach them.” The survey of dark energy, commonly referred to as DES, was performed by an international group of more than 400 scientists. The six-year survey produced one of the most comprehensive catalogs available …

The first quantum fluctuations set into motion a huge cosmic mystery

The first quantum fluctuations set into motion a huge cosmic mystery

Published by skeptic

Tiny oscillations in the early universe left a big mark on the universe Jozef Klopacka / Alamy The following is an extract from our Lost in Space-Time newsletter. Each month, we dive into fascinating ideas from around the universe. You can sign up for Lost in Space-Time here. “In the beginning”. These three words have cast quite a spell, ever since the 5th century AD when the Israelite priest known to biblical scholars as “P” put ink to parchment and wrote the opening lines of the Book of Genesis. Our modern telling of the creation story is no less poetic for being consistent with things we can observe in the universe today. Based on what we think we know, this is broadly how it goes. We have no words to describe the very beginning, because this is simply beyond physics and human experience. But we can extrapolate backwards from the present to say that the universe was formed in a hot big bang about 13.8 billion years ago. As it expanded, the very early universe suffered …