Theoretical astronomy at its simplest is the definition of terms to be applied to astronomical entities, sources, and objects.
Def. an "expanse of space that seems to be [overhead] like a dome" is called a sky.
Computer simulations are usually used to represent astronomical phenomena.
Part of the fun of theory is extending the known to what may be known to see if knowing is really occurring, or is it something else.
The laboratories of astronomy are limited to the observatories themselves. The phenomena observed are located in the heavens, far beyond the reach, let alone control, of the astronomical observer. “So how can one be sure that what one sees out there is subject to the same rules and disciplines of science that govern the local laboratory experiments of physics and chemistry?” “The most incomprehensible thing about the universe is that it is comprehensible.” - Albert Einstein.
- Philip B. Gove, ed. (1963). Webster's Seventh New Collegiate Dictionary. Springfield, Massachusetts: G. & C. Merriam Company. p. 1221.
- Narlikar JV (1990). Pasachoff JM, Percy JR, ed. Curriculum for the Training of Astronomers ‘’In: The Teaching of astronomy. Cambridge, England: Cambridge University Press.