What is the universe?

The universe is everything that exists, including all matter, energy, space, and time. It encompasses all galaxies, stars, planets, and other celestial objects, as well as all forms of radiation and other physical phenomena.

The origins and nature of the universe are still the subject of much scientific inquiry and debate, but the prevailing theory is that the universe began around 13.8 billion years ago in a cosmic event known as the Big Bang. According to this theory, the universe was initially in a hot, dense state and has been expanding and cooling over time.

The study of the universe and its properties is known as cosmology. Cosmologists use a variety of tools and methods, including observations of distant galaxies, the cosmic microwave background radiation, and gravitational waves, to understand the origins and evolution of the universe and to explore its many mysteries, such as dark matter and dark energy.