The researchers were able to probe the nature of the dark matter that surrounded the galaxies as it was 12 billion years ago. That’s billions of years earlier than we could ever see before. Scientists hope the ground-breaking findings could reveal the secrets of the still-mysterious dark matter that makes up an important part of our universe but is largely unknown. It has already offered tantalizing clues about the history of our world. The researchers say the findings indicate that the fundamental rules of the universe were different in its early years. As its name suggests, scientists cannot see dark matter directly because it does not emit light. Instead, scientists usually watch as light travels through the galaxies they want to investigate, measuring how it travels – the more it’s distorted, the more dark matter there is. However, the most distant galaxies – which we see as having existed billions of years ago – are too faint for this technique to work. The distortion cannot be properly detected and dark matter has remained impossible to analyze. This left scientists unable to probe dark matter more than 10 billion years ago. The time before that and the beginning of the universe, 13.7 billion years ago, remained impossible to understand. Now scientists say they have overcome this problem by using a different source: the microwaves released by the Big Bang. The team measured how these microwaves, instead of light, were distorted, and in doing so were able to see dark matter from the very beginning of the universe, looking at galaxies just after they were formed. “Most researchers use source galaxies to measure the distribution of dark matter from the present to eight billion years ago,” added Assistant Professor Yuichi Harikane of the University of Tokyo’s Cosmic Ray Research Institute. “However, we could look further back in time because we used the more distant CMB to measure dark matter. For the first time, we measured dark matter almost from the earliest moments of the universe.” The results showed a number of surprises, including how dark matter accumulated in the early universe. Theory suggests that dark matter should stick together and form clumps in the universe – but it was far less than predicted. “Our finding is still uncertain,” said Hironao Miyatake of Nagoya University, who led the team. “But if true, it would suggest that the whole model is flawed as you go further back in time. This is exciting because if the result remains after reducing the uncertainties, it could indicate an improvement in the model that may provide insight into the nature of dark matter itself.” An article describing the findings is published in Physical Review Letters.
