Measuring the Expansion of the Universe Through Changes in the CMB Photosphere

TL;DR

This paper proposes that future high-precision measurements of the CMB anisotropy, separated by a century, could directly observe the universe's expansion in real-time through changes in the CMB photosphere.

Contribution

It introduces a method to measure the universe's expansion by detecting changes in CMB anisotropy patterns over a century.

Findings

Potential to observe CMB anisotropy changes at l~900

Feasibility of measuring these changes with future detector arrays

Measurement separated by a century can reveal universe's expansion

Abstract

The expansion of the universe may be observed in ``realtime'' by measuring changes in the patterns of the anisotropy in the CMB. As the universe ages, the surface of decoupling--or the CMB photosphere--moves away from us and samples a different gravitational landscape. The response of the CMB to this new landscape results in a different pattern than we observe today. The largest change occurs at l~900. We show that with an array of detectors that we may envision having in a couple of decades, one can in principle measure the change in the anisotropy with two high precision measurements separated by a century.