Cosmology: universe not lumpy (Introduction)

by David Turell , Tuesday, August 08, 2017, 19:03 (2663 days ago) @ David Turell

The latest mapping of the universe shows that lumpiness is not present:

https://www.scientificamerican.com/article/cosmic-map-reveals-a-not-so-lumpy-universe/?...

"The new results, part of the ongoing Dark Energy Survey (DES), charted the distribution of matter in part by measuring the way that mass bends light, an effect known as gravitational lensing. The Universe was extremely smooth, with matter evenly distributed in its infancy nearly 14 billion years ago, but mass has been clumping together ever since into galaxies, gas clouds and other structures. Data released by the DES team on August 3 suggest that the clumping has happened more slowly than indicated by earlier estimates, which were based on baby pictures of the Universe made by measuring the cosmic microwave background, the afterglow of the Big Bang.

"The difference in the results produced by the two techniques is still within the margins of error in both sets of measurements, say the survey leaders. A smaller gravitational-lensing survey, the Kilo Degree Survey (KiDS) also found a similar discrepancy last year.

"Either way, the results show that DES is now reaching levels of precision that make it competitive with microwave-background surveys—including those by the European Space Agency's Planck satellite — says survey leader Joshua Frieman,

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"The latest study was based on the first year of data collection, in which DES mapped 26 million galaxies in the southern sky and measured their apparent shapes. The team then calculated the amount of gravitational lensing in each part of the sky to reconstruct the density of matter. The results confirm what has become the ‘standard model’ of cosmology, in which ordinary matter constitutes only 4% of the Universe’s contents. But the researchers find a slightly smaller amount of dark matter — about 26% — than Planck’s 29%, with the rest being taken up by ‘dark energy’, the stuff believed to be pushing the cosmos apart at an accelerating speed.

"Galaxies and dark matter are not spread uniformly across the Universe, and instead have been concentrating, under the pull of gravity, into a weblike structure of clusters and filaments, with enormous voids in between. The level of concentration measured by DES is 7% lower than what the standard model of cosmology predicts, based on Planck's data from the primordial Universe.

"If confirmed, this gap could mean that mass has been clumping at a lower pace than predicted, potentially revealing new physics. For example, it could point to unexpected interactions between dark matter and dark energy, or to new types of neutrinos.

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"Overall, researchers are excited to have an additional tool to probe the cosmos in ever-greater detail. “My own view of all of these measurements is that they are stunning tests of the cosmological model, and the precision and accuracy only keep getting better and better,” says astronomer Wendy Freedman of the University of Chicago.

"The latest map is based on DES's first round of observation, which began in 2013, and it covers about one thirtieth of the full sky, three times larger than a preliminary map the survey released in 2015. The final survey, due to conclude in 2018, will cover one-tenth of the sky; the results might appear some time in 2020, Frieman says. Ultimately, the goal of the DES is to map a large-enough region to see how the influence of dark energy has evolved over the Universe's recent history."

Comment: The smoothness finding is in favor of the inflation theory.