On the formation and propagation of pulses in ether

TL;DR

This paper discusses Euler's 18th-century theory of light propagation in ether, highlighting his analogy with sound in air, his attempt to determine ether's elastic properties, and his early estimation of light speed.

Contribution

It provides an annotated translation of Euler's work on pulse formation and propagation in ether, emphasizing his early insights and distinctions in wave motion theory.

Findings

Euler distinguished local fluid motion from pulse movement

He attempted to estimate the speed of light based on elastic properties

He recognized the analogy between light and sound propagation

Abstract

In 1746 Euler publishes E88 -- Nova theoria lucis et colorum (A new theory of light and colors) in five chapters. This is an annotated translation of Chapter II - De formatione ac propagatione pulsuum (On the formation and propagation of pulses in ether), in which Euler considers that the propagation of light in ether is similar to the propagation of sound in air. Based on the elastic properties of the air, he then tries to find the elastic properties of the ether, but, obviously, with no avail. Nonetheless, he correctly distinguished the local motion of the fluid particles from the motion of the pulse itself, and even attempted to estimate the speed of light.