Gravitational waves and cosmic expansion: similarities and differences

TL;DR

This paper compares gravitational waves and cosmic expansion within Einstein's general relativity, highlighting their similarities and differences through the metric of spacetime, emphasizing a simplified, accessible approach.

Contribution

It provides a conceptual comparison of gravitational waves and cosmic expansion focusing on the spacetime metric, clarifying their conceptual relationship.

Findings

Both phenomena are described by the spacetime metric.

The focus on the spatial part of the metric simplifies understanding.

Highlights differences in how the metric relates to physical properties.

Abstract

Gravitational waves and cosmic expansion are both described in terms of Einstein's general relativity. This article explores the similarities between the two phenomena, as well as some differences, using the fundamental concept of the metric of spacetime, expressed via a line element. In both contexts, the focus is on the metric description of space, as opposed to the components of the metric determining the properties of time. This allows for a simplified, more accessible discussion.