Skip to main content

About the Cosmic Microwave Background

The cosmic microwave background (CMB) is the relic radiation left over from an early hot phase in the history of the universe. Remarkable progress has been made in the characterization of the CMB after its initial discovery by Arno Penzias and Robert Wilson in 1965. Although the temperature of CMB is remarkably uniform throughout the universe, the temperature does have very small fluctuations depending on where in the sky one looks. A prediction of the inflationary model of the early universe, these small fluctuations (roughly one part in 100,000) were first measured by the Cosmic Background Explorer satellite in 1992. Characterizing these fluctuations to gain a deeper understanding of primordial fluctuations is a rapidly evolving field that has seen major advances from space-based missions, such as the Wilkinson Microwave Anisotropy Probe and the Planck satellites, and from ground-based observations by the Atacama Cosmology Telescope and the South Pole Telescope, among others. These results have provided independent evidence for the accelerated rate of expansion of the universe, propelled by a mysterious dark energy.”

About Argonne and CMB

Argonne’s CMB research includes fabrication of state-of-the-art superconducting sensors for the South Pole Telescope (SPT), next-generation readout technologies, and various topics in cosmology such as dark energy constraints based on measuring the hot gas in galaxy clusters and investigating the evolution of the universe via joint analysis of data from the CMB and from optical surveys, such as the Dark Energy Survey. Cosmological simulations carried out by Argonne theorists, now supported under the U.S. Department of Energy’s Exascale Computing Project, are an important aspect of the scientific thrust in this area.

All the detectors filling the focal plane in SPT-3G, the latest incarnation of SPT, were fabricated at Argonne. This work, which was a combined effort involving Argonne (the High Energy Physics, Materials Science, and Nanoscience and Technology divisions), Fermilab, and the University of Chicago, is continuing under Argonne’s Universe as Our Laboratory strategic initiative, with a view to develop and fabricate the detectors for CMB-S4, the next-generation (Stage 4) ground-based CMB experiment.

The CMB-S4 experiment will provide a dramatic leap forward in our understanding of the fundamental nature of space and time and the evolution of the universe. CMB-S4 will provide stringent new tests of the inflationary model of the universe, including the search for primordial gravitational waves, help determine the number and masses of neutrinos, constrain new light relic particles and test general relativity on large scales.