collision question

I haven’t played around with this engine in a while, but I find something a little puzzling. If I put a box and a plane below it and start the game engine with the box as an actor and the plane as a nothing, the box collides with the plane and stops. However, if I put another box that is designated as nothing and push the actor box with a force, it goes through the nothing box. It stops only if I lable the other box as an actor, too. Why is there collision with the plane when it’s not labled as an actor but not with the box?

Nevermind. They were out of alignment from the pespective I was in. There is collision with the box, too.