The universe is the entirety of everything that exists, including all matter and energy, space and time, and the physical laws and constants that govern them. It is thought to have begun with the Big Bang, a massive explosion that occurred approximately 13.8 billion years ago. This explosion caused the universe to rapidly expand and cool, leading to the formation of subatomic particles, atoms, stars, galaxies, and eventually planets and life as we know it.
The universe is still expanding today and is thought to be infinite in size. It is made up of a vast number of galaxies, which contain stars, planets, and other celestial bodies. Scientists believe that the universe contains a variety of different types of matter, including dark matter and dark energy, which make up most of the universe and have yet to be directly observed.
The study of the universe is known as cosmology, and scientists use a variety of tools and techniques, including telescopes and satellites, to study and understand its properties, origins, and ultimate fate.