The correct option is 1 and 3 only.
Explanation
The Big Bang Theory explains the origin and evolution of the universe. It postulates that the universe began from a singular point of infinite density and temperature approximately 13.7 billion years ago. The process involved a rapid initial expansion, followed by cooling and the eventual formation of matter.
Statement-wise Analysis
- Statement 1 is Correct. According to the Big Bang theory, the expansion of the universe was extremely rapid initially. Within fractions of a second after the explosion (a period known as inflation), the universe expanded exponentially before the rate of expansion began to slow down.
- Statement 2 is Incorrect. The formation of the first atoms occurred after the initial rapid expansion had slowed down.
- The initial expansion (inflation) lasted for a tiny fraction of a second.
- The expansion then slowed down significantly.
- The first atomic nuclei formed within the first three minutes, and neutral atoms formed roughly 300,000 years later. Both events occurred well after the initial rapid expansion phase had ended and the expansion rate had decelerated.
- Statement 3 is Correct. As the universe expanded, the energy density decreased, leading to a significant drop in temperature. This cooling was essential for the conversion of energy into matter, allowing subatomic particles and eventually atoms to form.
Key Takeaway
The Big Bang event was characterized by an initial fraction-of-a-second rapid expansion (inflation), followed by a slowdown and cooling period that allowed for the formation of atomic matter (nucleosynthesis and recombination) much later.