The discovery of the cosmic microwave background (CMB) in 1965 and the subsequent detection of minute ripples in the CMB in 1994 both garnered Nobel Prizes. The former confirmed the big bang models of the universe while ruling out the steady state models. The latter demonstrated how an initially smooth universe developed structures like clusters and superclusters of galaxies. The ripple discovery also provided strong indicators of where the early clumpiness originates—a period of hyperfast expansion in the earliest fractions of time after the creation of the universe. Additionally, the CMB provides a powerful tool to understand the gross features of the universe, such as its geometry, content, and age.
A recent article in Science highlights another important discovery arising from measurements of the CMB. The fluctuations observed in the CMB represent a density map of the universe when it was 380,000 years old. Over the next billion years, the regions of higher density became the clusters and superclusters of galaxies observed today. The first phases of this growth involved the dark matter, which comprises 22% of the universe’s energy budget, forming a cosmic filamentary web. The visible structures astronomers see formed at the junctions of this dark matter web.
As the CMB photons pass through space on their journey to Earth, the gravity pull of clusters of galaxies distorts their path slightly. Detecting these distortions will allow cosmologists to reconstruct this dark matter web from the period before galaxies formed. The original article posted on the arXiv preprint server describes in more detail the first detection of these gravitational distortions of the CMB.
Although more-detailed observations of the CMB and the large scale structure in the universe will be needed to give a clear picture of the early dark matter web, detecting the distortions is the first critical step down that path. As the picture becomes clearer, our knowledge of the early universe will grow dramatically. Additionally, RTB predicts this new tool will illuminate further evidence of fine-tuning to make the universe habitable.