Final answer:
The Big Bang theory is the primary cosmological model taught because it is supported by extensive evidence and explains a wide range of astronomical phenomena. Other theories have not stood the test of observation and experiment to the same extent, rendering the Big Bang theory the most scientifically validated explanation of the universe's beginning and expansion.
Step-by-step explanation:
The Big Bang theory is the primary theory taught in a typical astronomy class because it is the most comprehensive and widely supported explanation for the origin and evolution of the universe. This theory describes a singular event where space, time, matter, and energy erupted from a singularity approximately 13.8 billion years ago. The expansion of the universe, the cosmic microwave background radiation, and the abundance of light elements all serve as strong evidence for the Big Bang. Although there are other models like the steady-state theory, they have fallen out of favor due to lack of supporting observational evidence.
Challenges to the Big Bang theory, such as the precise balancing of the universe's density, have led to further developments in the model, incorporating concepts like dark energy and inflation. However, no other theory has yet matched the Big Bang in its ability to explain such a wide range of astronomical observations, from galactic redshifts indicating an expanding universe to the most perfect blackbody spectrum ever detected, which corresponds to the residual temperature from the Big Bang.
The dominance of the Big Bang theory in educational curricula reflects its status as the prevailing cosmological model among scientists today. It is the framework within which current research is conducted and hence offers students the most relevant and up-to-date understanding of cosmic history.