The universe is the entirety of all objects and spaces that exist in time and space. It is the largest known system and is believed to be approximately 13.8 billion years old.

Dark matter is a form of matter that cannot be seen directly but can be inferred by its influence on galaxy formation and the speed of star rotation. It is believed to make up 27% of the total mass of the universe.

The Big Bang is the event that marked the beginning of the universe, approximately 13.8 billion years ago. It is believed to have been a moment when the entire universe rapidly expanded from an infinitely dense and hot point.

Dark energy is a form of energy that cannot be seen directly but can be inferred by its influence on the universe's expansion. It is believed to make up 68% of the total energy of the universe.

The cosmic horizon is the farthest limit that can be seen from Earth. It is the most distant point visible due to the universe's expansion and the speed of light. All stars and galaxies beyond this point are beyond human sight.

The cosmic horizon is the farthest limit that can be seen from Earth. It is the most distant point visible due to the universe's expansion and the speed of light. All stars and galaxies beyond this point are beyond human sight.