In the Michelson and Morley experiment, when the two half-beams reached the screen, they shared the same space, a condition called interference.
The Michelson Interferometer
Interfering Waves
©2012 WGBH Educational Foundation. All Rights Reserved. Adapted from PlanetQuest: "SIM Lite Astrometric Observatory"/NASA/JPL. Images courtesy of Archival Photographic Files, apf6-00086, Special Collections Research Center, University of Chicago Library, and Library of Congress.