It sounds like vertigo.
The inner ear sends, for the lack of a better term, motion messages to the brain, as if you were moving, when you look up into a large space. The brain gets the illusion of movement when no movement is present, and you get dizzy.
Found something that may explain it better than I can.
Vertigo, or dizziness, is a symptom, not a disease. The term vertigo refers to the sensation of spinning or whirling that occurs as a result of a disturbance in balance (equilibrium). It also may be used to describe feelings of dizziness, lightheadedness, faintness, and unsteadiness. The sensation of movement is called subjective vertigo and the perception of movement in surrounding objects is called objective vertigo.
Vertigo usually occurs as a result of a disorder in the vestibular system (i.e., structures of the inner ear, the vestibular nerve, brainstem, and cerebellum). The vestibular system is responsible for integrating sensory stimuli and movement and for keeping objects in visual focus as the body moves.
When the head moves, signals are transmitted to the labyrinth, which is an apparatus in the inner ear that is made up of three semicircular canals surrounded by fluid. The labyrinth then transmits movement information to the vestibular nerve and the vestibular nerve carries the information to the brainstem and cerebellum (areas of the brain that control balance, posture, and motor coordination). There are a number of different causes for dizzy spells.