Universe

The Universe is all of time and space and its contents.The Universe includes planets, stars, galaxies, the contents of intergalactic space, the smallest subatomic particles, and all matter and energy. The observable universe is about 28 billion parsecs (91 billion light-years) in diameter at the present time. The size of the whole Universe is not known and may be infinite.12 Observations and the development of physical theories have led to inferences about the composition and evolution of the Universe.