Possible direct measurement of the expansion rate of the universe

TL;DR

This paper proposes a novel method to directly measure the universe's expansion rate by precisely observing the fluence changes of stable sources like galaxies over time, leveraging their abundance.

Contribution

It introduces a new observational approach using galaxy fluence measurements to directly determine the cosmic expansion rate, relaxing detector precision requirements.

Findings

Potential to measure expansion rate with relaxed detector precision.

Method benefits from the large number of galaxies available.

Feasibility of direct measurement through combined observations.

Abstract

A new method is proposed for directly measuring the expansion rate of the universe through very precise measurement of the fluence of extremely stable sources. The method is based on the definition of the luminosity distance and its change along the time due to the cosmic expansion. It is argued that galaxies may be chosen as the targets of the observation to perform the measurement. We show that, by simultaneously increasing the observation time and physically adding the fluences from different galaxies, the requirement on the relative precision of the detector for an observation of 1 second on a single galaxy can be relaxed to $10^{-5}$. Benefiting from the abundance of galaxies in the universe, the method may be quite promising.