The universe encompasses all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. It is the totality of everything that exists.

Here are some key aspects of the universe:

• Size and Expansion: The universe is vast and is continuously expanding. The observable universe, which is the portion we can see from Earth, is estimated to be about 93 billion light-years in diameter.
• Composition: The universe is composed of ordinary matter (baryonic matter), dark matter, and dark energy. Ordinary matter makes up only a small fraction of the total. Dark matter and dark energy are not directly observable and are not well understood.
• Origin: The prevailing cosmological model for the universe is the Big Bang theory. This theory suggests that the universe originated from an extremely hot, dense state about 13.8 billion years ago and has been expanding and cooling ever since.
• Structure: The universe has a hierarchical structure, with planets organized into solar systems, solar systems into galaxies, galaxies into groups, groups into clusters, and clusters into superclusters, forming large-scale structures like filaments and voids.

For more detailed information, you can refer to these resources:

• NASA - Universe Facts
• Space.com - Universe Facts