Chapter 26: Problem 24

What was the era of recombination? What significant events occurred in the universe during this era? Was the universe matter-dominated or radiation- dominated during this era?

Short Answer

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The era of recombination occurred about 378,000 years after the Big Bang and was the period when atoms first formed due to the universe cooling, allowing electrons and protons to combine. Significant events during this era include the formation of neutral hydrogen atoms and the universe becoming transparent, allowing photons to travel freely. During this era, the universe transitioned from being radiation-dominated to matter-dominated.

Step by step solution

Define the era of recombination

The era of recombination, also known as the era of decoupling, occurred about 378,000 years after the Big Bang. This era gets its name from the fact that this is the time when atoms first formed due to the cooling of the universe that allowed electrons and protons to combine.

Explain significant events during the era of recombination

One of the most significant events during the era of recombination was the formation of neutral hydrogen atoms. Before this era, the universe was too hot and dense for atoms to exist. Protons and electrons existed independently in what is known as a plasma. As the universe expanded and cooled, the electrons and protons were able to combine to form hydrogen atoms. Another notable event of this era is that, because the universe was no longer a plasma of charged particles, it became transparent rather than opaque. This allowed photons to travel freely through space, and the universe's background radiation we observe today was essentially 'released'.

Clarify whether the universe was matter or radiation dominated

In terms of matter or radiation dominance, at the time of the era of recombination, the universe was transitioning from being radiation-dominated to matter-dominated. During the very early stages of the universe, radiation energy was more prevalent because the universe was incredibly hot and dense. However, as the universe expanded and cooled, the balance shifted towards matter.

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What was the era of recombination? What significant events occurred in the universe during this era? Was the universe matter-dominated or radiation- dominated during this era?

Short Answer

Step by step solution

Define the era of recombination

Explain significant events during the era of recombination

Clarify whether the universe was matter or radiation dominated

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