by If you were to zoom out on the universe, far beyond the level of the planets, stars or galaxies, you would see a vast, flat expanse with no significant features. At least, that is the traditional view.
The principle that everything looks the same everywhere is a fundamental pillar of the standard model of cosmology, which aims to explain the big bang and how the universe developed in the 13.7bn years ago.
But this week a meeting of some of the world’s leading cosmologists will be held at the Royal Society of London to ask the question: what if this assumption is wrong?
The meeting comes after a number of high-profile astronomical observations have challenged conventional wisdom, according to Professor Subir Sarkar, a cosmologist at the University of Oxford and co-organiser of the meeting.
“We are, in cosmology, using a model that was first formulated in 1922,” he said. “We have great data, but the theoretical basis is past its sell-by date. More people are saying the same thing and these are respected astronomers.”
The conference brings together some of the scientists behind the recent anomalous findings. These include observations that suggest the universe is expanding faster in some regions than others, hints of megastructures in the night sky and evidence of cosmic streams – great celestial rivers of matter on a scale that cannot easily be accommodated. on it within normal limits.
Dr. Nathan Secretrest, of the US Naval Observatory and a collaborator of Sarkar, is presenting results that raise the possibility that the universe is a little weak. After analyzing a catalog of more than 1m quasars (extremely luminous galactic cores), the team found that one hemisphere of the sky appeared to host about 0.5% more sources than the other another.
It may not amount to a major discrepancy but, according to Sarkar, if confirmed it would undermine dark energy, which is supposed to be the main component of the universe. “It would mean that two-thirds of the universe has just disappeared,” Sarkar said.
Dr Konstantinos Migkas, from Leiden University, will share findings that the Hubble constant – the rate at which the universe is expanding – appears to vary across space. “Our findings add another problematic piece to the puzzle,” Migkas said. At least on a local scale, this suggests that observations do not match the predictions of the standard model. “We can’t extrapolate that it’s wrong across the entire globe,” he said.
Alexia Lopez, a PhD student at the University of Central Lancashire, has discovered cosmic megastructures, named Big Ring and Giant Arc. These shapes, traced out by galaxies and galaxy clusters, occur on a scale beyond which the universe should be flat and effectively featureless.
“When we find a list of structures that exceed this scale, are they challenging this assumption that is so fundamental in cosmology?” said Lopez. “Perhaps our standard model needs more critical analysis.”
Sarkar suggests that the belief in the standard model of cosmology is so deep that it is treated as “the religion”. “I am concerned that this principle has not been checked,” he said, although not everyone agrees with this characterization.
Professor George Efstathiou, an astrophysicist at the University of Cambridge, who is presenting a more skeptical approach at the conference, said it was not true that the model had not been repeatedly questioned. “People accuse me of defending the model,” he said. “But what they don’t realize is how much time I spent trying to disprove it. I totally disagree that it’s some groupthink.”
Efstathiou said that while it was interesting, none of the anomalies being presented were compelling enough to undermine standard theories. “The question is: how good is the data?” he said. For example, the necessary use of multiple telescopes to observe the different hemispheres of the sky may result in the warping of the universe, so that sifting through data to look for patterns would result in anomalies, he suggested. “The Great Circle in the sky, I certainly don’t believe in it,” he said.
Professor Wendy Freeman, who is presenting new results from the James Webb space telescope, said: “These are all exciting threads at different levels of significance. We need to explore further where, if anything, the standard mold breaks. I don’t think there’s anything obvious that will stand the test of time.”
This kind of vigorous debate is welcome at the conference. “I look forward to a lively discussion,” Sarkar said. “Let them come at him with everything they’ve got.”
