Step 1: Understanding the Problem:
The Big Bang Theory is the prevailing cosmological model explaining the origin and subsequent evolution of the universe from an infinitely dense, hot singular point.
Step 2: Approach and Formula:
Evaluate the sequential cosmological events proposed by the theory, particularly noting the timeline regarding the formation of fundamental elements relative to the initial explosion.
Step 3: Detailed Explanation:
- Option (A): It is true that the core purpose of the Big Bang Theory is to explain the origin of the universe.
- Option (B): Immediately following the singular explosion, the universe expanded violently and rapidly. As a direct physical consequence of this expansion, the overall extreme temperature came down. This is true.
- Option (C): It claims Hydrogen and Helium formed {before} the explosion. This is false. During the singularity phase, the extreme heat prevented the existence of any atoms. Matter, and eventually simple atoms like Hydrogen and Helium, formed {sometime after} the explosion as the universe sufficiently cooled down.
- Option (D): Over extensive periods, these newly formed, scattered Hydrogen and Helium gases slowly condensed due to gravitational forces, eventually forming the earliest stars and galaxies. This is true.
Step 4: Final Answer:
The incorrect statement is (C).