D6 Cosmic Background Radiation

Topic

This model centers on ground-based telescopes installed at the highest, driest available sites; these instruments measure the cosmic microwave background with fine angular resolution using arrays of thousands of superconducting bolometric detectors cooled by dilution refrigerators.

These telescopes have three primary objectives: measuring the Sunyaev-Zel'dovich effect in galaxy clusters as a probe of large-scale structure; measuring the polarization of the cosmic background to search for the imprint of primordial gravitational waves left by inflation; and measuring the gravitational lensing experienced by that same cosmic background to determine neutrino mass.

The most remarkable feature of these telescopes is their combination of extreme altitude—minimizing atmospheric water vapor that would otherwise absorb the microwave signal—and superconducting detectors so sensitive that the absorption of a single photon measurably alters their electrical resistance.

Deploying tens of thousands of these detectors increases mapping speed and sensitivity a hundredfold compared to the previous generation of instruments, yielding the most precise map available of the total mass integrated between us and the surface of last scattering. Thus, from the ground-based telescopes that open this document to the integrated mass map that concludes it—and encompassing the Sunyaev-Zel'dovich effect and superconducting detectors—ground-based measurements of the cosmic background radiation allow a single cosmic microwave background to simultaneously reveal the universe's large-scale structure, the imprint of inflation, and the mass of one of the most elusive particles in existence.

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