The moment a person starts to change in a small collective community, they don't show up as the memory that people have of them, like something's different, something's out of phase, right?
天文学百科 The Astronomy Book (Big Ideas Simply Explained)
When the beams meet each other again, they are exactly out of phase as they interfere and promptly disappear, unless a gravitational wave has passed through space while the beams were traveling.
But if the horizontal and vertical components were out of phase with each other, which might happen if you increase the phase shift in one of them, their sum might instead trace out some sort of ellipse.