Scientists can’t agree on how clumpy the universe is
The universe is surprisingly smooth. A new measurement reveals that the universe is less clumpy than predicted, physicists report in a series of papers posted July 30 at arXiv.org. The discrepancy could hint at something amiss with scientists’ understanding of the cosmos. To pin down the cosmic clumpiness, researchers studied the orientation of 21 million galaxies with the Kilo-Degree Survey at the Paranal Observatory in Chile. As light from those galaxies streams through the universe, its trajectory is bent by massive objects, a phenomenon called gravitational lensing. This lensing causes the elongated shapes of galaxies to appear slightly aligned, rather than oriented randomly. When combined with additional data from other sky surveys, that alignment quantifies how much the matter in the universe is clumped together. The researchers found that the universe is about 10 percent more homogenous, or smoother, than predicted based on light released just after the Big Bang, the cosmic microwave...