“There’s probably some missing physics somewhere, but nobody has been able to come up with it yet,” says Freedman. The eBOSS study agrees with the CMB method, which deepens the puzzle. Our two main ways of calculating it – using the ancient cosmic microwave background (CMB) versus a local measurement of the movement of nearby objects – always disagree. This is a measure of the rate of expansion of the universe. “Things are fitting together remarkably well, with the exception of the Hubble constant,” says Wendy Freedman at the University of Chicago. However, one existing conflict has been exacerbated by the survey. As predicted by lambda-CDM, space-time as a whole seems to be flat, not curved. The team also constrained the shape of the universe 10 times more tightly than our next best set of observations. It didn’t quite nail it down, but the measurement was as precise as the best ground-based neutrino experiments. The development of large-scale structure is partly dependent on the behaviour of particles known as neutrinos in the early universe eBOSS was able to constrain their mass, which is a big outstanding problem in physics. Some past measurements have hinted that what we see in the universe may not match that model’s predictions, but the eBOSS map shows no conflict at all. Our leading approach to understand how the universe went from mostly homogeneous to clumpy is a model called lambda-CDM. Read more: Cosmological crisis: We don’t know if the universe is round or flat This lets us watch giant structures such as galaxy clusters forming. The team observed galaxies and quasars, which are the bright centres of some galaxies, and used their red shifts – changes in light due to them moving away from us – to measure distances and the rate of and expansion of the universe. Astronomers from the Sloan Digital Sky Survey. Quasars are in red and nearer galaxies in yellow. “There isn’t anything else with that range of coverage and that allows us to fill this 11-billion-year gap between the ancient and recent universe,” says Kyle Dawson at the University of Utah, who leads the extended Baryon Oscillation Spectroscopic Survey (eBOSS) team at SDSS. A slice through the largest 3-D map of the universe to date. This new survey looks deep enough to map 80 per cent of the universe’s 14-billion-year history. Light travels at a finite speed, so looking into space also means peering back through time. Captured by the Sloan Digital Sky Survey (SDSS), it has bolstered our leading picture of the cosmos, even though it deepens one enduring mystery. The Sloan Digital Sky Survey used a 2.5-metre telescope in New Mexico to capture the biggest map of the universeĪ huge 3D map depicts 11 billion years of cosmic history and places the tightest constraints ever on our best model of the universe.
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