Final answer:
The particle era is the phase in the universe's early history where subatomic particles were frequently created and destroyed, ending when matter overcame antimatter as the universe cooled.
Step-by-step explanation:
The era of the universe you are asking about is called the particle era, a tumultuous period during which subatomic particles were constantly being created and destroyed. During this time, the universe was akin to a 'seething cauldron,' with photons (particles of light) colliding and interchanging energy, sometimes being annihilated to create particle-antiparticle pairs. These particles, in turn, frequently collided, and when matter particles met with antimatter particles, they would annihilate each other, converting into a burst of gamma-ray radiation. The particle era ended when the universe cooled down enough to prevent the formation of these pairs from photons, leading to a predominance of matter over antimatter.
As the universe expanded and cooled, the conditions allowed for the creation of larger particles, such as electrons and positrons. The temperature of the universe during this era was extremely high, exceeding 10¹⁴ K initially, which enabled the creation of various subatomic particles, including those that later contributed to dark matter. Eventually, temperatures fell to a point where it became cool enough for electrons to combine with nuclei and form neutral atoms, a process marking the end of the particle era and the beginning of the recombination era.