The Big Bang theory describes the universe's origin from an extremely hot, dense state around 13.8 billion years ago, followed by rapid expansion and cooling that continues to this day.
During the first fraction of a second—an era called inflation—the universe expanded exponentially, smoothing and flattening space. After inflation ended, the universe consisted of a highly energetic plasma of particles and radiation.
Within minutes, protons and neutrons combined to form light elements (hydrogen, helium, deuterium, and small amounts of lithium) in a process known as Big Bang nucleosynthesis.
About 380,000 years after the Big Bang, the universe cooled enough for electrons and nuclei to combine into neutral atoms. This allowed photons to travel freely, producing the Cosmic Microwave Background—the oldest light we can observe.
Over time, gravity amplified slight density variations in the plasma, leading to the formation of stars, galaxies, and large-scale structures.
Key evidence supporting the Big Bang includes the expansion of space (observed via galaxy redshifts), the abundance of light elements, and the precise measurements of the Cosmic Microwave Background by missions such as COBE, WMAP, and Planck.
Modern cosmological models (ΛCDM) incorporate dark matter and dark energy, explaining current observations of cosmic acceleration, geometry, and composition.
14 November 2012
Could you tell the story of human existence in a minute? This thrilling video culls together multiple teasing snippets in an attempt to do just that. And sets it to music. Briefly depicted, from start to finish, is an artistic animation of the Big Bang, a trip across the early universe, the formation of the Earth and Moon, the emergence of multi-celled life and plants, the rise of reptiles and dinosaurs, a devastating meteor strike, the rise of mammals and humans, and finally the rise of modern civilization. The minute movie ends with a flyover of the modern skyscraper and a human standing atop a snow covered mountain. The above video is the latest from the Symphony of Science project. Gallery: Yesterday's Total Solar Eclipse Challenge: Can you identify the skyscraper at 1:18 and the snow-covered mountain at 1:25?