Why does a beam of laser light stay pencil-thin when sent into the stratosphere or to the moon? I鈥檓 aware that the photons move in waves in unison, but why doesn鈥檛 the wave component spread laterally as well, such as waves on the surface of the ocean normally do?
Martin Line, Mermaid Waters, Queensland, Australia
We pay 拢25 for every answer published in New Scientist. To answer this question 鈥� or ask a new one 鈥� visit newscientist.com/lastword. Terms and conditions apply.
Advertisement
This article appeared in print under the headline 鈥淟aser thin鈥�