One of the most accurate surveys of the universe’s structure has suggested that it is “less lumpy” than expected, in findings that could indicate mysterious forces at work.
Notes written by Dark Energy Survey and the South Pole Telescope Charting the distribution of matter with the aim of understanding the competing forces that have shaped the evolution of the universe and governed its ultimate fate. The extraordinarily detailed analysis adds to a body of evidence that suggests there may be a crucial component missing from the so-called Standard Model of Physics.
“It looks like there are a few fewer [clumpiness] Eric Baxter, an astrophysicist at the University of Hawaii and co-author of the study, said:
The results did not pass the statistical threshold that scientists consider strong enough to claim a discovery, but they follow similar results from previous surveys that suggest a chasm could be opening between theoretical predictions and what is actually happening in the universe.
“If the result holds up, it’s very exciting,” said Dr. Chihuai Chang, an astrophysicist at the University of Chicago and lead author. “The whole point of physics is to test and break models. The best case scenario is that it helps us understand more about the nature of dark matter and dark energy.”
Since the Big Bang 13 billion years ago, the universe has been expanding, but matter has also been cooling and coalescing as gravity pulls denser regions together, creating a cosmic web of galaxy clusters and filaments. As scientists worked to make sense of this cosmic tug of war, a strange picture emerged in which only about 5% of the contents of the universe is explained by ordinary matter. Roughly 25% is so-called dark matter, which is invisible mass that contributes to gravity, but is otherwise invisible. The remaining 70% is dark energy – a mysterious phenomenon that is said to explain why the expansion of the universe is accelerating rather than slowing down due to gravity.
The latest work uses data from the Dark Energy Survey, which has surveyed the sky over six years from a mountaintop in Chile, and the Antarctic Telescope, which looks for faint traces of radiation traveling across the sky from the first few moments of the universe. Either way, the analysis uses a phenomenon called gravitational lensing, in which light bends slightly as it passes massive objects, such as galaxies and dark matter clumps, allowing scientists to infer the distribution of matter in the universe.
Separately, scientists can infer the structure of the very early universe from the heat left over from the big bang and use computational models to “fast forward” and see if the models match up with the observations.
Analysis indicates that the material is not as “lumpy” as might be expected. According to Professor Carlos Frink, a cosmologist at Durham University who was not involved in the research, there are three possible explanations. First, it could be a result of noise in the data or a systematic error in the telescope. It is also possible that rather than a major rewriting of cosmological theory, a poorly understood astronomical phenomenon could explain the results. “For example, supermassive black holes in the centers of galaxies can produce huge jets of radiation that could, in principle, push matter around and smooth it out a bit,” he said.
A third, more exciting option, is that the discrepancy is explained by entirely new physics, such as the existence of new types of neutrinos, the strange behavior of dark energy, or unconventional forms of dark matter. “Of the three possibilities, I hope it’s the last, I’m afraid it’s the second, but I suspect it’s the first,” Frink said.
Results Published in Physical Review D.
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