The ultimate cosmic question: How fast is the universe expanding?
The universe is expanding. But how fast? Why is this happening? And what will be the universe's ultimate fate?
These are big, literally cosmic questions, and astronomers continue to struggle to nail down the answers. Different techniques for measuring what is called the Hubble Constant — the rate at which the universe is expanding — keep coming up with different estimates.
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CBS News
28-04-2025
- CBS News
Chicago astronomist, professor named one of Time Magazine's Most Influential People of 2025
Alongside Snoop Dogg and Demi Moore, a Chicago professor and astronomist was named one of Time Magazine's 100 Influential People of 2025. Wendy Freedman is a professor of astronomy and astrophysics at the University of Chicago. Time recognizes her research in observational cosmology, or the study of direct observations, using instruments like telescopes, to examine evidence of the universe's development and structure. Freedman and her team created a new Hubble Constant, a unit of measurement used to describe how fast the universe is expanding. It is considered one of the most critical numbers in cosmology because it can determine the universe's age and could even reveal potential new physics. Her work has been recognized within the science community, but this is her first "public" recognition. "It was a complete surprise when I learned about it. I am honored to be on this list," she said. "I feel very grateful to the University of Chicago for giving me the opportunity to study what I do and all the people and my teams over the years that have made this possible. It's not a solitary endeavor," Freedman said. The concept of the Hubble Constant originated from a Belgian physicist in 1927, and then Edwin Hubble provided the first observational evidence of it. Since then, NASA has recognized four women, including Freedman, behind the Hubble Space Telescope's achievements. "This measurement was one of the primary justifications for building a space telescope," according to NASA. The Hubble Space Telescope Key Project is the name of the international team she co-led to refine the Hubble Constant. April 24th marked 35 years of the Hubble Telescope in space. NASA celebrated the milestone by releasing photos of galaxies and planets. Freedman's observations are among the 1.6 billion observations made by the Hubble. Freedman was also the first woman to join the Carnegie Observatories as a permanent scientific staff member. She began her work there initially as a postdoctoral fellow. She also helped launch the Giant Magellan Telescope Project and served as the chair of the board of directors for over a decade. Planetary Nebula NGC 2899, Hubble Telescope NASA Being a woman scientist in the middle of a significant debate in cosmology does not come without controversy. "What people had been arguing about was whether the Hubble constant was 50 or 100, and we were able to make that measurement with 10% accuracy, which, for the time…was a huge step forward," she said. She said controversy can be good because it keeps scientists accountable. "Science is a field that self-corrects. You get better measurements that supersede the older ones. That's one of the reasons why I love science," she said. So, what's next? "As you make more and more accurate measurements, you unearth other kinds of things that could be causing a difference. So that's where we're actively involved now, and that is another controversy. We're trying to understand how exciting this is, because it would be very exciting if it were something new and fundamental about the universe that we didn't understand before," she said. The list is divided into six categories: innovators, titans, artists, icons, leaders, and pioneers. "We have artists, musicians, scientists, and writers. Human capacity for doing things is really very vast. I think it's nice that all of those kinds of things get recognized because it's who we are," Freedman said. Some other people on the list are Gisèle Pelicot, a French woman who survived years of sexual assault by her husband and over 50 men, whose case took the world by storm, as well as Tedros Adhanom Ghebreyesus, the Director-General of the World Health Organization, and Robert Montgomery, who "revolutionized organ transplantation, expanding access and improving outcomes for patients worldwide." There are also controversial people on this list, including six members of the Trump Administration, including President Trump. "TIME's founders knew that focusing on the individuals who are transforming the world is the best way to help readers understand it," Sam Jacobs, Editor-In-Chief of Time, wrote in the explainer of how Time chooses the 100 people. "
Yahoo
17-04-2025
- Yahoo
The universe isn't just expanding—it may be spinning
The prevailing consensus in astrophysics is that the universe has spent the past 13-or-so billion years expanding outward in all directions, ever since the Big Bang. It's expanding at this very moment, and will continue to do so until… a number of possible theoretical endings. Meanwhile, the specific rate at which the universe is growing remains a longstanding point of contention known as the 'Hubble tension.' However, there may be a way to finally ease that tension—you just need to put a slight spin on everything. In simplest terms, the rate at which the universe expands on paper doesn't match actual astronomical observations. That speed—called the Hubble Constant—is measured in units of kilometers per second per megaparsec (km/s/Mpc), with a megaparsec measuring about 300,000 light years. The most widely accepted theoretical model, the Lambda/Cold Dark Matter model (ΛCDM), says the universe is growing at 67-68 km/s/Mpc. But what astronomers see through their equipment is a little faster, at about 73 km/s/Mpc. And therein lies the Hubble tension. In a study published in the April issue of the Monthly Notices of the Royal Astronomical Society, a team of researchers including experts at the University of Hawai'i's Institute for Astronomy argue that introducing a miniscule amount of rotation to standard mathematical model of the universe may provide the way to align both expansion theories.'Much to our surprise, we found that our model with rotation resolves the paradox without contradicting current astronomical measurements,' study co-author and astrophysicist? István Szapudi said in a statement. 'Even better, it is compatible with other models that assume rotation.' In addition to its mathematical compatibility, the concept also doesn't break any of the known laws of physics. The problem is detecting this spin, given just how slowly the universe may be turning. But while it is difficult to discern with current tools, the spin is still fast enough to influence the expansion of space over the eons. Szapudi and their colleagues' new model indicates the universe finishes a single rotation once every 500 billion years—meaning there's still quite a bit of time before the universe completes its first full circuit. 'To paraphrase the Greek philosopher Heraclitus of Ephesus, who famously said 'Panta Rhei' (everything moves), we thought that perhaps 'Panta Kykloutai,' everything turns,' said Szapudi. Looking ahead, astronomers hope to construct a full computer model of the universe based in part of their new theory. From there, they will hopefully be able to pinpoint signs of cosmic spinning to search for among the stars.
Washington Post
19-03-2025
- Washington Post
Cosmologists intrigued by signs the universe might stop expanding
The fate of the universe is still very much up in the air. Right now it is expanding, at an accelerating rate. If nothing changes, many billions or trillions of years from now the universe would presumably become cold, dark and inhospitable. But new data posted online Wednesday by scientists with the Dark Energy Spectroscopic Instrument (DESI) survey suggest this process of cosmic acceleration — attributed to a mysterious energy field dubbed 'dark energy' — has been weakening over the past 4 billion to 5 billion years. Dark energy may not be a 'cosmological constant,' as generally assumed, but rather may evolve over time, according to the DESI scientists. If this idea of 'evolving dark energy' holds up under further investigation, it would put many different cosmic futures in play. Perhaps the universe will settle down into a serene maturity, never in a rush, imperturbable. Or perhaps the acceleration will pick up again, as if someone turned a knob somewhere. Or perhaps everything will go into reverse, and the whole business will contract again. That would be the ultimate turnaround — a cosmic 180. 'This result brings to the table, again, the possibility that the universe may not continue to expand forever. One of the possibilities now is that, in some theories, the universe could stop expanding, and re-contract into a Big Crunch,' said Mustapha Ishak, a cosmologist at the University of Texas at Dallas and co-chair of the working group that analyzed the data. 'We can't foretell what dark energy will do in the future,' added Willem Elbers, a cosmologist at England's Durham University and a co-chair of the working group. Dark energy is the primary driver of cosmic evolution, but if that mysterious energy field decays, matter and gravity could become the dominant factors, he said. 'In that case, the ultimate fate hinges on a knife's edge. Depending on how space is curved, a collapse is possible,' he added in an email. For planning purposes, it is important to recognize that the timescale here is many billions or trillions of years. The DESI observations may be cosmically consequential but do not rise to the level of an action item for us mortals. As observational data pours in, theoretical cosmologists have some work to do. There continues to be uncertainty about the Hubble Constant, the rate of the universe's expansion, and whether there's something glitchy in the estimates or, more profoundly, something wrong with the standard model for the evolution of the cosmos. Different estimates of the expansion rate have led to a decade-long debate dubbed the Hubble Tension. New telescopes are coming online to try to discern what the universe is telling us about its past and future. NASA's Nancy Grace Roman Space Telescope is under construction at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and is on track for launch in two years. Later this year, the Vera C. Rubin Telescope in Chile, funded by the National Science Foundation and the Department of Energy, is scheduled to begin observations. NASA's SPHEREx space telescope, a relatively modest observatory, launched March 11. It will survey 450 million galaxies, testing theories that the embryonic universe underwent a period of exponential acceleration known as 'cosmic inflation.' DESI, funded by the Department of Energy's Office of Science and managed by the Lawrence Berkeley National Laboratory, is an international collaboration involving 900 researchers and 70 institutions worldwide. The experiment uses a telescope at Kitt Peak in Arizona to map the history of the universe. Its dataset includes 13.1 million galaxies and 1.6 million quasars, which are very bright, distant objects powered by supermassive black holes. So there's a lot of data coming in, and the universe clearly hasn't run out of ways to surprise cosmologists. 'I think the universe is giving us a lesson in cosmic humility. It doesn't seem to be following the manual we had,' Adam Riess, a cosmologist at Johns Hopkins University who shared the Nobel Prize in physics for discovering the accelerated expansion of the universe, said in an email. Riess is not part of the team that published the new data. 'When a similar but slightly weaker version of this DESI result first appeared last year, many were not sure if this clue would sustain another year's scrutiny and tripling of the data, but it has!' he said. 'If confirmed, it literally says dark energy is not what most everyone thought, a static source of energy, but perhaps something even more exotic.' If the DESI news sounds vaguely familiar, it is because last April the same team announced a similar result. The difference is the quantity of the data — more than twice as many galaxies studied — and the confidence in the result. The team is still not claiming a 'discovery,' but the probability that the results will hold up with further study is increasing. Although the new data has been posted online, it has not yet been published in a peer-reviewed journal. 'We are still at the 'interesting' or 'stay tuned' level. Very intriguing but not yet definitive,' cosmologist Wendy Freedman of the University of Chicago, who is not part of the DESI team, said in an email. On Tuesday, another team of scientists, the Atacama Cosmology Telescope collaboration, posted online the results of observations of the most ancient light in the universe — the cosmic microwave background radiation. In a news release, the team described the data as 'the clearest and most precise images yet of the universe's infancy.' The radiation was emitted 380,000 years after the Big Bang, when the expanding universe first became transparent to light. Jo Dunkley, a Princeton astrophysicist, said in an email that the new data supports the standard model in cosmology, called Lambda Cold Dark Matter. It does not rule out the possibility of evolving dark energy as suggested by the DESI results so far, she said. 'I think that until we figure out what dark energy is, almost anything is in play — i.e. the dark energy could change its behavior in the future in a way that leads to a Big Crunch, even though that's not what the simpler models would suggest,' she said.
