Final answer:
The 'freezing out' of the strong force at 10^-38 seconds after the Big Bang refers to the separation and emergence of the strong force as a distinct entity from the unified forces due to the cooling of the universe.
Step-by-step explanation:
When we say that the strong force "froze out" at 10-38 second after the Big Bang, we are referring to the process similar to liquids or gases freezing and turning into solids at certain temperatures. In the early universe, when temperatures were significantly higher, all the fundamental forces (strong, weak, electromagnetic, and gravity) were unified into one single force. However, as the universe expanded and cooled, these forces began to take on distinctive characteristics and separate from one another at different times and temperatures in the universe's history.
The strong force, responsible for holding the nuclei of atoms together, separated from the other forces during the early stages of the universe, marking its unique and individual characteristics, and this separation is what is colloquially known as the strong force 'freezing out.' This event occurred shortly after the inflationary epoch, and it played a crucial role in the development and shaping of the universe as we observe it today.