At an age of 380,000 years,the temperature of the universe had fallen to 3000 K,and electrons could then combine with protons to produce hydrogen gas instead of roaming freely through space.What major transition occurred as a consequence of this change in the universe at this time?
A) The universe would have lost its electrical charge suddenly to become electrically neutral.
B) The present laws of physics were applicable to the properties of the universe for the first time.
C) The universe became transparent to light for the first time.
D) Nuclear fusion no longer occurred below this temperature,so general fusion throughout the universe would have ceased.

Question

Quizplus · Accepted Answer

At an age of 380,000 years, the temperature of the universe had fallen to 3000 K, allowing electrons to combine with protons to form neutral hydrogen atoms. This caused the universe to become transparent to light for the first time. Prior to this, the universe was filled with a dense fog of ionized gas that scattered and absorbed light, making it impossible to see through. The formation of neutral hydrogen atoms allowed light to travel freely through the universe, making it transparent.

At an Age of 380,000 Years,the Temperature of the Universe