A hundred thousand years after the Big Bang, helium hydride formed the first molecule. By about t + 370,000 years, neutral ...

This process gradually cleared the fog of neutral gas, allowing ultraviolet light to travel freely and making the universe transparent to light. Observation Techniques: 21-centimeter radio waves ...

By about t + 370,000 years, neutral hydrogen formation had wound itself down, leaving the Universe transparent for the first time. But not all the matter formed by Big Bang nucleosynthesis ...