Mechanics and common sense
Mechanics and common sense
The combination of reason and common sense lead one astray in science.

Consider Newton's laws of motion. Newton's first law says that when you set an object in motion that it remains in motion and at constant speed when force is removed. Everyday experience contradicts this. The existence and nature of friction aren't obvious, nor is it trivial to conceive a frictionless world.

Everyday experience is that heavenly motion differs from motion on Earth. Common sense doesn't easily reconcile the differences.

A hollow polystyrene ball 5 inches in diameter weighs less than an ounce. A depleted uranium ball 5 inches in diameter weighs more than 10 pounds. Common sense dictates that the latter will fall faster. Common sense overlooks "inertia". In the absence of inertia one's common sense would prevail. If inertia were proportional to the square of mass, the polystyrene ball would fall faster!

Understanding requires patience, reflection, knowledge of mechanism and, in the case of the natural world, experimental testing. Mechanics is best understood by contructivism and not easily understood by memorizing.