On The Relativity of Redshifts: Does Space Really "Expand"?

TL;DR

This paper critically examines the concept of expanding space in cosmology, analyzing how redshifts of photons are understood through Einstein's general relativity, revealing both simplicity and complexity in the phenomenon.

Contribution

It challenges the conventional notion of space expansion by providing a nuanced analysis of redshifts within Einstein's framework, questioning the physical reality of expanding space.

Findings

Redshifts can be understood without assuming space expansion.

The nature of cosmological redshift is more complex than the simple stretching of space.

Implications for interpreting observational data in cosmology.

Abstract

In classes on cosmology, students are often told that photons stretch as space expands, but just how physical is this picture? Does space really expand? In this article, we explore the notion of the redshift of light with Einstein's general theory of relativity, showing that the core underpinning principles reveal that redshifts are both simpler and more complex than you might naively think. This has significant implications for the observed redshifting of photons as they travel across the universe, often refereed to as the cosmological redshift, and for the idea of expanding space.