"<a href=""https://www.youtube.com/watch?v=tozuzV5YZ7U&amp;t=0m43s"">0:43</a> I paused the video to make a prediction about how this is possible", and my prediction is that the laser is pulsing on and off with specific timing so that the camera's rolling shutter will capture the laser only where they want it visible. (Kind of like the experiment with dripping water in front of a speaker or flashing light.)