The origin of the universe precedes the origin of life because the universe itself began first, setting the stage for the conditions necessary for life to develop much later.
- The universe originated about 13.8 billion years ago with the Big Bang, an event where all space, time, matter, and energy suddenly came into existence from a hot, dense state called a singularity
. This event marks the beginning of time and space itself, so nothing existed "before" the universe in a temporal sense
- After the Big Bang, the universe expanded and cooled, allowing subatomic particles to form, which then combined into atoms like hydrogen and helium during a process called nucleosynthesis within the first few minutes
. Over billions of years, these atoms formed stars, galaxies, and eventually planets.
- Life, by contrast, emerged much later—on Earth about 3.5 billion years ago—from complex chemical reactions among biomolecules in a suitable environment
. This means life arose from nonliving matter after the universe and Earth had already existed for billions of years.
Thus, the timeline is: first the universe originated, creating the physical conditions and elements necessary for planets and chemistry; then, billions of years later, life emerged on at least one of those planets. The origin of life depends on the prior existence of the universe and its physical components, so it necessarily follows the origin of the universe
