Is Cosmology just a theoretical subject?

Technically, YES! Cosmology attracts only the most genius of minds for a reason. Cosmology is a subject that is just in its nascent stages and it’ll be decades or even centuries before it becomes as extensive as physics or biology. It basically deals with the creation, continuity, and end of the universe. These three are not easily provable concepts.

Other than the universe, cosmology also deals with the working of space and time which again becomes a part of the unknown. Modern cosmology derives most of its knowledge with the Big Bang Theory as its backdrop or initiating point. If somehow, the Big Bang Theory is disproven, cosmology will have to start all over again.

Most cosmologists are philosophers with a scientific outlook. There are two types of cosmologists- one who give theories and the others who try to prove it.

Cosmology had been making headway, into a new age of discovery and proof due to the contributions of scientists like Stephen Hawking, but the theoretical and maybe literal existence of dark energy has stopped it dead in its tracks. Dark energy is to cosmology what quantum mechanics is to physics.

Hence, overall cosmology is mostly a speculative aspect of physics and its status as a science is often debated.Until and unless, cosmology doesn’t provide an enhanced model of the Big Bang Theory, which solves its criticisms, cosmology might not ever get out of that debate.

Just? You certainly need to be a keen and deeply thinking theorist to even tackle cosmology as a subject. Not surprisingly, this had been the realm of philosophers. To move towards discovery does depend upon a total and advanced grasp of scientific theory before delving into the vast expanse of logical thinking required to even envisage the possibilities of space and time.

Only by the very thorough setting up of a theory can a cosmologist begin to seek to prove or disprove it, thereby advancing our knowledge of the universe. If you read Hawking's progress through such mental activity, you will get an idea of how theories become scientific studies and their proofs result in new knowledge.