Light, delayed: The Shapiro Effect and the Newtonian Limit

TL;DR

This paper discusses the gravitational time delay known as the Shapiro effect, exploring its theoretical foundations, simplified derivations, and potential astrophysical measurements, highlighting its role in understanding the Newtonian limit and post-Newtonian corrections in general relativity.

Contribution

It provides simplified derivations of the Shapiro effect and gravitational redshift, and discusses astrophysical scenarios for measuring the effect, enhancing understanding of the Newtonian limit in relativity.

Findings

Simplified derivations of the Shapiro effect and gravitational redshift.

Identification of astrophysical situations where the Shapiro effect can be measured.

Insights into the Newtonian limit and post-Newtonian corrections in general relativity.

Abstract

The Shapiro effect, also known as the gravitational time delay, is close kin to the gravitational deflection of light that was the central topic of our Summer School. It is also an interesting test bed for exploring a topic that provides the foundations for most of the calculations we have done in this school, yet is highly complex when treated more rigorously: the question of the Newtonian limit, and of the post-Newtonian corrections that must be applied to include the leading-order effects of general relativity. This contribution discusses simplified derivations for the gravitational redshift and the Shapiro effect, as well as astrophysical situations in which the Shapiro effect can be measured.