The VSL Discussion: What Does Variable Speed of Light Mean and Should we be Allowed to Think About ?

TL;DR

This paper discusses the controversial concept of variable speed of light (VSL) theories, examining historical examples and addressing criticisms related to their validity and consistency with special relativity.

Contribution

It provides a historical overview and critical commentary on VSL theories, highlighting their conceptual challenges and debates within physics.

Findings

VSL theories have faced criticism for tautologies and relativity violations.

Historical examples include Einstein's 1911 VSL attempts and Dicke's electromagnetic theory.

The paper offers insights into the ongoing debate and conceptual issues surrounding VSL theories.

Abstract

In the past years, variable speed of light (VSL) theories have been of growing interest but also a subject of controversial discussion. They have been accused both for tautologies and for violating special relativity, and concerns have been expressed about the validity of such approaches in general (e.g. Ellis, astro-ph/0703751). Without trying completeness on the issue, the example of Einstein's VSL attempts (1911) and Dicke's `electromagnetic' theory (1957) are urges to give some comments on the above criticism.