I never really thought very deeply about the concept of frame of reference as it related to physics before. I kind of just took it for granted. But the more I think about, the more puzzling it becomes.
Take pic related, you’re in a truck trailer, the truck is moving, you’re passing someone, they see you moving but from your perspective you yourself are standing still. It’s everything else that is moving.

Is there some space-time bending fuckery going on when this happens that we can’t fully grasp like with Gravity or am I just thinking about this too much?