How can one, being on Earth, understand that it (and not the sky) rotates?

Most of the experiments that make it possible to understand this are associated with the appearance of the Coriolis force: oscillations of the Foucault pendulum, the deflection of shells when firing from a cannon, the deflection of falling bodies from the vertical. The other part is related to the effects of centrifugal force: the flattening of the Earth and the change in the value of the acceleration of gravity with a change in latitude.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.