The universe began about 13.8 billion years ago with an event known as the Big Bang. According to this theory, the universe started as a tiny, extremely hot and dense point-a singularity-that suddenly expanded rapidly. This expansion caused space itself to grow, and as the universe expanded, it cooled down, allowing the formation of the simplest elements like hydrogen and helium

. Key points about the beginning of the universe:

• Edwin Hubble’s observations in the 1920s showed that galaxies are moving away from each other, indicating the universe is expanding. This implied that the universe was once much smaller and denser, leading to the idea of the Big Bang

• After the Big Bang, the universe was initially a hot gas mostly composed of hydrogen and helium. Over billions of years, gravity pulled this gas together to form stars, galaxies, and eventually planets

• The earliest moments involved the formation of subatomic particles, matter-antimatter annihilation, and nucleosynthesis, where light elements formed within the first few minutes

• Around 380,000 years after the Big Bang, the universe cooled enough for neutral atoms to form, allowing photons to travel freely. This event left behind the cosmic microwave background radiation, which is the oldest light we can observe today

While the Big Bang theory explains the expansion and evolution of the universe from this initial hot dense state, what caused the Big Bang itself remains a mystery

. In summary, the universe began as a tiny, hot, dense fireball that exploded and expanded, leading to the formation of all matter and cosmic structures we see today