What is the most abundant element in the universe?

Hydrogen is the most abundant element in the universe, comprising roughly 75% of the elemental mass of the universe. It is the primary building block of stars, which are formed from clouds of hydrogen gas that undergo gravitational collapse, leading to nuclear fusion. This process not only makes hydrogen essential for star formation, but it also plays a vital role in the synthesis of heavier elements through stellar nucleosynthesis.

Hydrogen's abundance is a result of its simplicity and lightness, allowing it to be the first element formed after the Big Bang. As the universe expanded and cooled, hydrogen atoms combined to form the first stars, perpetuating its dominance. In contrast, elements like oxygen, carbon, and nitrogen, while important for terrestrial life and stellar processes, are far less abundant in the cosmos. They are typically produced within stars and supernova events, which occur much later in the universe's timeline compared to the formation of hydrogen. This process of element creation underscores the unique and foundational role hydrogen plays in the cosmos.