they do collide, but without the physical effect.
compare it with slapping someone in the face. your hand will go trough his face and you both know that your hand hit's his face, but without the bruises and pain :p
i used that for an older experiment with doors, where i could walk "through" the door but still the player knew that it was colliding with the door and so trigger the next scene event.[/quote]
I understand that there still is collision behavior, but no collision physically.
But, right now, neither the person nor the beam has any collision behavior, which you'll see if you downloaded the game. Therefore, the beam shouldn't do anything to the person. However, despite being a sensor with no collision behaviors, the beam still "pushes" the people down for some reason.