What is big-bang theory?

Explanation

### Step-by-Step Text Solution:

1. **Definition of the Big Bang Theory**: The Big Bang Theory is a scientific explanation for the origin of the universe, proposing that it began from a singular, extremely hot and dense point approximately 13.8 billion years ago.

2. **The Great Explosion**: According to the theory, this singular point underwent a massive explosion, often referred to as the "Big Bang." This explosion marked the beginning of time and space as we know it.

3. **Separation of Cosmic Materials**: Following the explosion, the cosmic materials, which include non-living elements such as carbon, oxygen, iron, helium, and hydrogen, were dispersed. These materials were divided into numerous pieces and began to move away from each other.

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