I'm trying to intuitively understand curl of a vector field, and I was watching this video. In it, they present the following scenario:
I'm curious as to why the curl is zero in the four squares that are zero. They are two arrows pointing in the same direction, shouldn't that contribute twice the curl to a particle at a given point, and not cancel the other arrow out? I just don't see how the two arrows in the same direction cancel each other out, unless maybe it has to do something similar to how two torques applied in the same direction at opposite ends will produce no net torque.