Dec 27, 2025 · The most widely accepted explanation for the origin of the universe is the big-bang theory, which proposes that the universe began approximately 13.8 billion years ago in an extremely …

Discoveries in the early 20th century lead to the Big Bang theory with a hot fireball, cooling and becoming less dense as the universe expanded, allowing the first subatomic particles and simple …

Oct 22, 2024 · Around 13.8 billion years ago, the universe expanded faster than the speed of light for a fraction of a second, a period called cosmic inflation. Scientists aren’t sure what came before inflation …

Jul 17, 2025 · At first, the dense, fast-expanding universe was full of superheated electrons and protons whizzing around, creating a sort of murky, searingly hot soup. But roughly 400,000 years after the …

Jan 18, 2017 · How did the universe begin—and what were its early days like? The most popular theory of our universe's origin centers on a cosmic cataclysm unmatched in all of history—the big bang.

Jul 26, 2025 · The story of how the universe began is the story of how everything came to be. It is not just the domain of physicists and philosophers, but a tale that pulses in the blood of every human …

In the first moments after the Big Bang, the universe was extremely hot and dense. As the universe cooled, conditions became just right to give rise to the building blocks of matter – the quarks and …

A depiction of the universe's 13.8 billion-year history, with the Big Bang at the left and the present day at the right. Researchers seek indirect ways to study the first instants of cosmic history, which are …

The Big Bang was the moment 13.8 billion years ago when the universe began as a tiny, dense, fireball that exploded. Most astronomers use the Big Bang theory to explain how the universe began.

The current accepted model of the history of the universe is based on the concept of the Big Bang: the universe started hot and dense then expanded and cooled. Different particles interact during each …