Photons without borders: quantifying light pollution transfer between territories

TL;DR

This paper explores how light pollution from distant sources affects local sites, emphasizing the importance of accounting for long-range photon transfer in managing and reducing light pollution effectively.

Contribution

It introduces methods to quantify and visualize the impact of remote light sources, especially focusing on municipal contributions to local light pollution levels.

Findings

Light pollution transfer can occur over hundreds of kilometers.

Municipalities significantly influence local light pollution levels.

Quantitative tools help identify major sources of light pollution.

Abstract

The light pollution levels experienced at any given site generally depend on a wide number of artificial light sources distributed throughout the surrounding territory. Since photons can travel long distances before being scattered by the atmosphere, any effective proposal for reducing local light pollution levels needs an accurate assessment of the relative weight of all intervening light sources, including those located tens or even hundreds of km away. In this paper we describe several ways of quantifying and visualizing these relative weights. Particular emphasis is made on the aggregate contribution of the municipalities, which are -- in many regions of the world -- the administrative bodies primarily responsible for the planning and maintenance of public outdoor lighting systems.