For me it is the fact that our blood contains iron. I earlier used to believe the word stood for some ‘organic element’ since I couldn’t accept we had metal flowing through our supposed carbon-based bodies, till I realized that is where the taste and smell of blood comes from.
Gravity makes up for what it lacks in force with its range and also the exponential nature from things getting attracted to each other forming a point of more potent attraction and so on (it was more relevant in the beginning of the universe, but we’re still feeling its effects)