How Far Can Laser Light Travel?

Have you ever played with a pocket-sized laser, wondering how far its light would travel? Could you, a naughty student inside a classroom on Earth, annoy a poor substitute teacher on Mars by waggling your laser pointer at him?​ Image Credit: Abigail Malate, Staff Illustrator,Inside Science.© American Institute of Physics The dimmest light visible to the naked eye in perfect darkness is around one ten-billionth of a watt per square meter. However, with the presence of urban light pollution, on...