universets

The universe is the totality of space, time, matter, energy, and the physical laws that describe them. It includes all galaxies, stars, planets, and structures, as well as the empty space between them.

The observable universe refers to the region from which light has had time to reach Earth since the Big Bang, about 93 billion light-years in diameter. The full universe may extend beyond that, possibly infinitely.

The current consensus is that the universe began with the Big Bang about 13.8 billion years ago. Initially extremely hot and dense, it expanded and cooled, allowing formation of subatomic particles and simple nuclei, followed by atoms, stars, and galaxies.

The universe's energy budget is roughly 5% ordinary matter, 27% dark matter, and 68% dark energy. Ordinary matter makes up stars, planets, and living beings.

The large-scale structure is shaped by gravity and dark matter, leading to filaments and voids. The expansion of space is accelerating due to dark energy, inferred from supernovae and CMB observations.

Cosmology uses general relativity, quantum physics, astronomy, and observations of the cosmic microwave background, supernovae, and large-scale surveys to study the universe's properties, age, geometry, and fate. Debates include the exact nature of dark energy and whether a multiverse exists.